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Arrowleaf sida (Sida rhombifolia L.) is a weed that has a fibrous stem, aggressive root system and waxy leaves that can hinder herbicide absorption. Based on knowledge of the environmental requirements for germination of this species, it is possible to predict emergence to assist in integrated management. The aim of this investigation was to characterize the air temperature and soil water potential requirements for arrowleaf sida germination, to model the emergence in the field using thermal and hydrothermal time models and to evaluate the longevity of the arrowleaf sida seed bank. Laboratory experiments were conducted to determine the temperature and water potential for seed germination by testing eight temperatures (10, 15, 20, 25, 30, 35, 40, and 45 °C) and 10 water potentials (0, −0.05, −0.1, −0.2, −0.4, −0.6, −0.9, −1.2, −1.5, and −2.0 MPa). Field experiments were conducted between 2014 and 2018 to model the emergence using three sampling times (starting on 10/20, 11/10, and 12/01), during which soybean seeds were sown. To evaluate the longevity and persistence of the seed bank, a factorial experiment was conducted, in which the first factor included three burial depths (0, 3, and 6 cm) and the second factor included five collection times (0, 1, 4, 10, and 16 months) after seed burial. The base, optimal and maximum temperatures for arrowleaf sida germination were 10.0, 24.8, and 42.5 °C, respectively, and the base water potential was −1.20 MPa. It is possible to predict the emergence of arrowleaf sida in the field by hydrothermal and thermal time models under different environmental conditions. In addition, this species has a persistent seed bank, with 30% of seeds being viable after 16 months of burial. [ABSTRACT FROM AUTHOR]

Climate change models predict temperature increases, which may affect germination, an important stage in the recruitment of individuals in agroecosystems. Therefore, it is crucial to conduct research on how temperature will impact the germination of multipurpose native species. Leucaena diversifolia (Schltdl.) Benth. is native to America and is commonly cultivated around the world due to having a high protein content in seeds, and their trees are used in agrosilvopastoral systems because they fix nitrogen and provide shade and cattle feed. However, climate change affects the critical phases of its life cycle and influences its growth, reproduction, phenology, and distribution. To assess the germination performance of Leucaena diversifolia under different temperatures throughout thermal times, we estimated germination variables and determined cardinal temperatures and thermal time; we also analysed germination and potential distribution under two climate change scenarios. We found significant variations in seed germination (78–98%) and differences in cardinal temperatures (Tb = 5.17 and 7.6 °C, To = 29.42 and 29.54 °C, and Tc = 39.45 and 39.76 °C). On the other hand, the sub-optimal and supra-optimal temperature values showed little differences: 51.34 and 55.57 °Cd. The models used showed variations in germination time for the analysed scenarios and the potential distribution. We confirm that the populations and distribution of L. diversifolia will be altered due to climate changes, but the species retains the ability to germinate under warmer conditions. [ABSTRACT FROM AUTHOR]

Wild edible fruits are important genetic and economic plant resources. They represent a significant livelihood resource for the population and are valuable in coping with climate change and food poverty. This work aimed to model the potential distribution of ten species of wild edible fruits from the state of Veracruz. These species were modelled with present and future climate scenarios. To obtain the projections, we used the MaxLike R library and bioclimatic variables from the WorldClim database under climate change scenarios with two radiative forcing trajectories (RCP4.5 and 8.5), and forecasts from three general circulation models (CCSM4, GISS.E2-R and MPI-ESM-LR) for the horizons 2050 and 2070. Then, we explore the spatial coincidence of the potential distribution of the fruits with geographic areas of Veracruz with high levels of marginalization, aiming to support the design of adaptative strategies to climate change. Pithecellobium dulce is the only species that will likely increase its current potential distribution in the future. The rest of the studied species Celtis caudata, Cordia dodecandra, Crataegus mexicana, Hymenaea courbaril, Manilkara sapota, Prunus serotina and Psidium guajava are projected to reduce their distribution area by more than 40%. The species Pouteria sapota and Pimenta dioica, of great economic value, could reduce their geographic area up to 82% and 85%, respectively. Municipalities with low to very low marginalization have the possibility of picking between four and six species on average, with potential of establishing in their surroundings. The analysed species are multipurpose, contribute to food security and are an alternative in adapting to climate change because they are candidates to be included in conservation initiatives while confronting the problem of marginalization. [ABSTRACT FROM AUTHOR]

Climate change models predict temperature increases, which may affect germination, an important stage in the recruitment of individuals in agroecosystems. Therefore, it is crucial to conduct research on how temperature will impact the germination of multipurpose native species. Leucaena diversifolia (Schltdl.) Benth. is native to America and is commonly cultivated around the world due to having a high protein content in seeds, and their trees are used in agrosilvopastoral systems because they fix nitrogen and provide shade and cattle feed. However, climate change affects the critical phases of its life cycle and influences its growth, reproduction, phenology, and distribution. To assess the germination performance of Leucaena diversifolia under different temperatures throughout thermal times, we estimated germination variables and determined cardinal temperatures and thermal time; we also analysed germination and potential distribution under two climate change scenarios. We found significant variations in seed germination (78–98%) and differences in cardinal temperatures (Tb = 5.17 and 7.6 °C, To = 29.42 and 29.54 °C, and Tc = 39.45 and 39.76 °C). On the other hand, the sub-optimal and supra-optimal temperature values showed little differences: 51.34 and 55.57 °Cd. The models used showed variations in germination time for the analysed scenarios and the potential distribution. We confirm that the populations and distribution of L. diversifolia will be altered due to climate changes, but the species retains the ability to germinate under warmer conditions.

Societal Impact Statement Exceptionally rainy winters and hot–dry summers are becoming the new normal around the United Kingdom. The effects of these climatic changes can already be seen in forests and grasslands, agricultural fields and even in our own gardens, as native plants try to keep pace with them. In this study, the seed germination of the native flora of Wakehurst, in the Southeast England, was analysed to identify potential threats to the long‐term persistence of selected species, which are part of the natural landscape of this area. Recommendations are provided for ecological restoration interventions which aim to maintain the different potential benefits those plants can provide to people. Summary Seeds play an important role in plant adaptation to human‐driven climate change. In this study, we applied a multilevel modelling of thermal germination responses of native temperate plants, to understand how global warming could affect their reproduction and the potential benefits they provide, as part of their natural capital. We identified Wakehurst (Southeast England, UK), as our study system. We modelled thermal seed germination parameters of the native flora as a whole and according to different uses categories (e.g., medicinal or food plants), through a phylogenetic meta‐analysis of publicly available data from Kew's Millennium Seed Bank (MSB). We also carried out a comparative germination study for MSB seed lots of 20 selected species. Finally, we quantified the germination risk, by comparing current and predicted environmental temperatures with thermal germination parameters at flora, uses categories and species level. Under future climatic scenarios, germination of the native flora will be at higher risk in spring than in autumn. Fitted quadratic models, although affected by phylogeny, did not show major differences among uses categories. Species with a narrow window of cold germination temperatures could be more at risk than those with warm optimal temperatures. Restoration activities should target species from phylogenetically clustered uses categories, to avoid losing their benefit provisions, and implement climate‐smart seed sourcing for high‐risk species. This multilevel germination modelling approach, based on collections and available data from conservation seed banks, can be applied to selected floras and regions to inform climate‐smart ecological restoration activities, while accounting for their natural capital.

Abstract Key message We have examined thermal control for embryo growth and seed germination in European ash. Using historical data (span of 36 years) of embryo index in matured seeds, we showed that maturation is not influenced by the annual average temperature. Secondary dormancy in ash’s seeds is easily induced, and the thermal window for both embryo growth and seed germination was between 10 and 20 °C. Context Seed germination plays a crucial role in establishing plant communities. Ash seeds are characterized by deep morphophysiological dormancy, usually overcome by 32 weeks of stratification. Observed climate changes might disrupt ash’s thermal window for embryo growth and seed germination. Thus, proper examination of seed adaptability can be important for forest management. Aims We investigated the effect of temperature on the embryo index (ratio between embryo and seed length) as well as embryo growth and germination of European ash (Fraxinus excelsior L.) seeds under different thermal conditions. Methods We used seeds collected at the same site in Poland between 1985 and 2021 to first analyze the influence of the growing season on the initial embryo index in mature seeds. Subsequently, we examined embryo growth and germination of seeds at constant temperatures of 3°, 10°, 15°, 20°, 25°, and 30 °C from seeds collected in 2021. Using the modeled rate of embryo growth and germination, we predicted the cardinal temperatures for those processes in ash seeds. Results The embryo index of ash seeds varied; however, there was no relationship between the index and year of seed collection. The base temperature for embryo growth was 1.4 ± 1.1 °C, with a ceiling temperature of 29.9 ± 2.0 °C and an optimal temperature of 15.7 ± 0.3 °C. The base temperature for germination was at − 1.8 ± 0.3 °C. Due to the induction of secondary dormancy, the ceiling temperature of germination was impossible to establish. Conclusions The initial embryo index of mature ash seeds seems to be an individual trait and was not affected by local average annual temperatures. The most effective temperature ranges for embryo growth and germination were similar, however narrow (between 10 and 15 °C). Temperatures above 20 °C inducted secondary dormancy, hampering embryo growth as well as germination. Such a narrow thermal window for embryo growth can potentially act as a limiting factor for the natural regeneration of ash seeds.

Amaranthus blitoides S. Watson and A. hybridus L. are common herbaceous annual summer weeds in different regions of Iran, which produce a large number of small seeds per plant. The goal of these experiments was to determine seed germination cardinal temperature and investigate the effect of constant temperature, osmotic and salt stresses, stratification, flooding duration, after‐ripening and seed planting depth on seed germination and seedling emergence. Two‐piece segmented, dent‐like and beta four‐parameter models were used to investigate the relationship between germination rate and constant temperature. The dent‐like model showed the best description of the effect of constant temperature on seed germination rate of both A. blitoides and A. hybridus. Optimal seed germination of A. blitoides occurred at 35°C, but in A. hybridus optimum germination was observed in a range of constant temperatures from 30 to 40°C. Osmotic and salt stresses and flooding adversely affected seed germination of both species. After ripening for 6 months increased germination percentage of both A. blitoides and A. hybridus. Maximum seedling emergence of A. blitoides (42.8%) and A. hybridus (44.9%) occurred at a planting depth of 3.3 cm, whereas further increased planting depth minimized seedling emergence of both weeds. Information obtained from this study will help us to develop effective techniques for management of A. blitoides and A. hybridus. [ABSTRACT FROM AUTHOR]

Introduction: The germination process is one of the most critical stages of a plant's growth and determines the success of the emergence of a weed in an agroecosystem, as it is the first stage in which the weed competes for a niche. Various environmental factors including temperature and moisture, affect the germination of weed seeds. Modeling techniques are capable of predicting germination, seedling emergence, and establishment of weed species. The ability to predict weed germination in response to environmental conditions is very effective for the development of control programs. The present research was conducted to determine the cardinal temperature and evaluate the best model for quantifying the response of the germination rate of western ragweed weed seeds under different water stress conditions. Materials and Methods: A factorial experiment was conducted in the form of a completely randomized design with three replications. The investigated factors included temperature at eight levels (5, 10, 15, 20, 25, 30, 35, and 40 C˚) and water potential at six levels (0, -0.3, -0.6, -0.9, -1.2, and -1.5 MPa) on the germination of western ragweed. In order to quantify the response of western ragweed germination rate to temperature, three non-linear Dent-like, Beta, and Segmented regression models were used. Results: The results showed that the effect of temperature, water potential, and their interactions on maximum germination, germination rate, and time required to reach 10, 50, and 90 percent germination were significant. Also, the results showed that by increasing the temperature from 10 to 25 C˚, the percentage and rate of germination increased whereas by increasing water potential, the percentage and rate of germination decreased. During the comparison of the models, based on RMSE, R², CV, and coefficients a and b parameters, the Beta model was the most suitable for estimating the cardinal temperatures of western ragweed. The base, optimum, and ceiling temperatures using the Beta model were 3.88, 25, and 40 C˚, respectively. Conclusions: The use of the Beta model to quantify the germination response of western ragweed seeds to different levels of water potential at different temperatures had acceptable results. Therefore, it is possible to predict the germination rate at different potentials. using the output of these models at different temperatures. [ABSTRACT FROM AUTHOR]

Societal Impact Statement: Exceptionally rainy winters and hot–dry summers are becoming the new normal around the United Kingdom. The effects of these climatic changes can already be seen in forests and grasslands, agricultural fields and even in our own gardens, as native plants try to keep pace with them. In this study, the seed germination of the native flora of Wakehurst, in the Southeast England, was analysed to identify potential threats to the long‐term persistence of selected species, which are part of the natural landscape of this area. Recommendations are provided for ecological restoration interventions which aim to maintain the different potential benefits those plants can provide to people. Summary: Seeds play an important role in plant adaptation to human‐driven climate change. In this study, we applied a multilevel modelling of thermal germination responses of native temperate plants, to understand how global warming could affect their reproduction and the potential benefits they provide, as part of their natural capital.We identified Wakehurst (Southeast England, UK), as our study system. We modelled thermal seed germination parameters of the native flora as a whole and according to different uses categories (e.g., medicinal or food plants), through a phylogenetic meta‐analysis of publicly available data from Kew's Millennium Seed Bank (MSB). We also carried out a comparative germination study for MSB seed lots of 20 selected species. Finally, we quantified the germination risk, by comparing current and predicted environmental temperatures with thermal germination parameters at flora, uses categories and species level.Under future climatic scenarios, germination of the native flora will be at higher risk in spring than in autumn. Fitted quadratic models, although affected by phylogeny, did not show major differences among uses categories. Species with a narrow window of cold germination temperatures could be more at risk than those with warm optimal temperatures. Restoration activities should target species from phylogenetically clustered uses categories, to avoid losing their benefit provisions, and implement climate‐smart seed sourcing for high‐risk species.This multilevel germination modelling approach, based on collections and available data from conservation seed banks, can be applied to selected floras and regions to inform climate‐smart ecological restoration activities, while accounting for their natural capital. [ABSTRACT FROM AUTHOR]

Key message: We have examined thermal control for embryo growth and seed germination in European ash. Using historical data (span of 36 years) of embryo index in matured seeds, we showed that maturation is not influenced by the annual average temperature. Secondary dormancy in ash's seeds is easily induced, and the thermal window for both embryo growth and seed germination was between 10 and 20 °C. Context: Seed germination plays a crucial role in establishing plant communities. Ash seeds are characterized by deep morphophysiological dormancy, usually overcome by 32 weeks of stratification. Observed climate changes might disrupt ash's thermal window for embryo growth and seed germination. Thus, proper examination of seed adaptability can be important for forest management. Aims: We investigated the effect of temperature on the embryo index (ratio between embryo and seed length) as well as embryo growth and germination of European ash (Fraxinus excelsior L.) seeds under different thermal conditions. Methods: We used seeds collected at the same site in Poland between 1985 and 2021 to first analyze the influence of the growing season on the initial embryo index in mature seeds. Subsequently, we examined embryo growth and germination of seeds at constant temperatures of 3°, 10°, 15°, 20°, 25°, and 30 °C from seeds collected in 2021. Using the modeled rate of embryo growth and germination, we predicted the cardinal temperatures for those processes in ash seeds. Results: The embryo index of ash seeds varied; however, there was no relationship between the index and year of seed collection. The base temperature for embryo growth was 1.4 ± 1.1 °C, with a ceiling temperature of 29.9 ± 2.0 °C and an optimal temperature of 15.7 ± 0.3 °C. The base temperature for germination was at − 1.8 ± 0.3 °C. Due to the induction of secondary dormancy, the ceiling temperature of germination was impossible to establish. Conclusions: The initial embryo index of mature ash seeds seems to be an individual trait and was not affected by local average annual temperatures. The most effective temperature ranges for embryo growth and germination were similar, however narrow (between 10 and 15 °C). Temperatures above 20 °C inducted secondary dormancy, hampering embryo growth as well as germination. Such a narrow thermal window for embryo growth can potentially act as a limiting factor for the natural regeneration of ash seeds. [ABSTRACT FROM AUTHOR]

ABSTRACT Palm trees are propagated almost exclusively by seeds and each species germinates under a certain temperature range. In this sense, the two-way thermogradient plate may be used to determine temperature limits for germination and seed response to temperature. The objective was to define the alternating temperature regime promoting higher and faster seed germination of Carpentaria acuminata and Phoenix canariensis palms using a two-way thermogradient plate. This equipment allowed 64 combinations of alternating and constant temperatures, ranging from 6.97 to 36.42 ºC for C. acuminata, and 7.96 to 35.94 ºC for P. canariensis. Seeds were sown in Petri dishes (25 x 9 cm) containing 1% water agar. Linear regressions were estimated to determine cardinal temperatures. After 50 days, non-germinated seeds were transferred from the two-way thermogradient plate to a germination chamber at 30 °C. The temperature regime promoting highest seed germination percentage of C. acuminata was 30.45/33.00 °C (day/night), with minimum, optimum, and maximum temperatures of 9.13, 28.53, and 36.33 °C, respectively. For seed germination of P. canariensis, the most appropriate temperature regime was 29.77/17.93 °C (day/night), with minimum, optimum, and maximum temperatures of 9.53, 28.03, and 35.43 °C, respectively.

IntroductionThe length of the growth period is the key to crop adaptation to new environments. It is strongly affected by the environment in such a way that it is possible to predict the length of the growing period based on some correlations with environmental factors. Simple models that quantify intraspecific variability in flowering responses to temperature and photoperiod can be useful for characterizing lines. Quinoa (Chenopodium quinoa) shows considerable resistance to a wide range of abiotic stresses. Cardinal temperatures and day length at each development stage are necessary to find an appropriate model for predicting plant growth and development.Materials and MethodsTen separate experiments (10 planting dates included: 29 March, 29 April, 28 May, 28 June, 26 July, 23 August, 6 September, 20 September, 29 January, and 29 February) were conducted as randomized complete block design with three replications. The experimental factor consisted of five quinoa lines plus one cultivar (Titikaka). Five promising lines were modified at Yazd Salinity Research Center. Four lines belong to the middle maturing group, one to the late maturing group, and the Titikaka cultivar belongs to early maturing group. The time of beginning and end of each developmental stage, including germination, pollination, and seed maturity, was recorded. The response of developmental stages to temperature and photoperiod was used to determine the cardinal temperature and day length of the main developmental stages (emergence, flowering, and seed maturity).Results and DiscussionBased on the coefficient of determination (R2) it seems that the quadratic model is suitable for estimating the cardinal temperatures of germination, flowering, and ripening of quinoa seeds. Using both quadratic and segmented models to estimate the length of special days resulted to satisfactory robustness. The results showed that on days with a length of lesser than 12 hours and temperatures lesser than 30°C, the flowering rate increased with a simultaneous increase of temperature and day length. As the day length increased to 14 hours, the rate of flowering development changed more significantly when temperatures were between 19 and 25°C than at temperatures below 19°C. For all lines, increasing the day length or temperature resulting in an increased plant maturation rate (from flowering to seed maturity) at a constant temperature or day length. The optimal temperature range for all developmental stages of quinoa lines was between 20 and 25°C. There was a significant difference in the base temperatures of the developmental stages. The base temperature for germination of quinoa lines was above 0°C, the base temperature for flowering was between -2 and +2°C, and the base temperature for seed maturity was below 0°C. The maximum temperature of all quinoa developmental stages was above 40°C (42-51°C). At low temperatures, the flowering stage was more sensitive than the seed ripening stage. The critical day length for flowering and seed ripening of quinoa lines was between 11.5 to 12 hours.ConclusionsThe optimum temperature range for germination was obtained by 25-34°C, for flowering by 28-21°C, and for seed ripening by15-32°C. The optimum temperature of all developmental stages of quinoa lines was between 20 and 25°C. The optimum day length range for flowering is estimated at 11.37-34.12 hours and for seed ripening by 10.58-12.3 hours. Using the segmented and quadratic models to estimate quinoa cardinal temperature and photoperiod response resulted in the same estimations, although in most values, the quadratic model showed a higher coefficient of determination. In general, the results indicated that the temperature and day length have a compensatory effect on the flowering rate and seed ripening stages of the studied lines.

Seed germination is a complex physiological process influenced by abiotic stresses such as drought, temperature, salinity along with other biological and physical means. Halothermal time model (HaloTT) permitted quantitative assessment of seed germination at different water potential (ψ) and temperature (T). The present study aimed to evaluate the reliability of HaloTT model and to find cardinal temperature values for seed germination of Oats under various Ts and ψs. Avena sativa L. Var. Swan seeds were incubated at seven constant Ts under five various ψs prepared through sodium chloride (NaCl) at Plant Physiology Lab., University of Peshawar, Pakistan. The cardinal Ts measured through HaloTT model for Oats seed germination were 10, 30 and 40 °C for the base (Tb), optimum (To) and ceiling (Tc) temperatures correspondingly in distilled water (0 MPa). The maximum halotime constant (θHalo) was recorded as 48 MPa °Ch−1 at 30 °C in distilled water (0 MPa). The highest value of halotime and thermal time of germination rate was observed at -2.0 MPa at 40 °C. Germination percentage (GP), germination rate index (GRI), germination energy (GE), coefficient of velocity of germination (CVG), timson germination index (TGI), mean germination rate (MGR) and coefficient of variation of germination time (CVt) was observed maximum in 0 MPa at 30 °C, while minimum in -2.0 MPa at 40 °C. Contrarily the high rate of mean germination time (MGT) and time to 50 % germination (T50 %) was reported in -2.0 MPa and -1.5 MPa at 10 and 40 °C, while in distilled water (0 MPa) is lowest at 25 and 30 °C. Thus, we concluded that HaloTT model precisely interpret germination responses to various ψs across different Ts and may be used as an accurate and simple method to predict germination parameters under natural field conditions.

Germination of castor seeds of seven dwarf hybrid genotypes, compared to a 'Local' genotype, selected from a Tunisian population by the University of Catania well adapted to the Mediterranean environment, were studied at six different temperatures (8, 12, 16, 25, 32, and 40 °C). The results indicate that the optimal temperature (25 °C) and near-optimal temperature (32 °C) are the best temperatures for ensuring castor germination (final germination percentage (FGP) ≥ 82.81%). Furthermore, these temperatures positively influenced the vigour index (VI) and the radicle elongation. At a temperature of 8 °C, no germination occurred, while temperatures of 12 and 40 °C negatively affected the seed germination, which, in some genotypes, was null or negligible (<21.25%). A temperature of 16 °C allowed good results to be reached for the FGP and the other considered parameters. Overall, the dwarf hybrids performed better at high temperatures than at low temperatures, thus, making them suitable for late sowings, with the exception of the genotype 'C1020', which resulted the best performance at 16 and 40 °C, being suitable for both early and late sowings. On the other hand, the 'Local' castor genotype, being the best-performing genotype at 12 and 16 °C, and the most tolerant to low temperature (base temperature (Tb) 12.1 °C), could be used in the early sowing in spring. [ABSTRACT FROM AUTHOR]

Palm trees are propagated almost exclusively by seeds and each species germinates under a certain temperature range. In this sense, the two-way thermogradient plate may be used to determine temperature limits for germination and seed response to temperature. The objective was to define the alternating temperature regime promoting higher and faster seed germination of Carpentaria acuminata and Phoenix canariensis palms using a two-way thermogradient plate. This equipment allowed 64 combinations of alternating and constant temperatures, ranging from 6.97 to 36.42 ºC for C. acuminata, and 7.96 to 35.94 ºC for P. canariensis. Seeds were sown in Petri dishes (25 x 9 cm) containing 1% water agar. Linear regressions were estimated to determine cardinal temperatures. After 50 days, non-germinated seeds were transferred from the two-way thermogradient plate to a germination chamber at 30 °C. The temperature regime promoting highest seed germination percentage of C. acuminata was 30.45/33.00 °C (day/night), with minimum, optimum, and maximum temperatures of 9.13, 28.53, and 36.33 °C, respectively. For seed germination of P. canariensis, the most appropriate temperature regime was 29.77/17.93 °C (day/night), with minimum, optimum, and maximum temperatures of 9.53, 28.03, and 35.43 °C, respectively. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the thermal requirements and compare methods for estimating leaf emergence in Annona squamosa L. under different shading conditions during the dry and rainy seasons in a transition region between the Cerrado Amazon biomes, Mato Grosso, Brazil. Seedlings were grown under full-sun conditions (reference) and black polyolefin screens with 35%, 50%, 65%, and 80% attenuation of global radiation. Basal temperatures were determined using the method of least standard deviation; accumulated thermal sum was estimated using the method described in Ometto (1981); the relationship between number of leaves and thermal sum were evaluated using the phyllochron and Wang & Engel (1998) models. The minimum and maximum basal temperatures for the growth of A. squamosa were 11.0 and 38.0 °C, respectively. The accumulated thermal sum presented small variation between shading conditions and seasons, resulting in means of 1744±44 and 4434±118 degree-days at 113 and 260 days after transplanting (DAT), corresponding to the end of the dry and rainy seasons, respectively. The thermal requirement for leaf emergence varied among the different shading conditions, with higher phyllochrons under full sun conditions and 80% shading (109.8 °C day leaf-1) and lower phyllochrons under 50% shading (91.74 °C day leaf-1). The phyllochron model presented higher efficiency in estimating leaf emergence compared to the Wang & Engel model. Growing A. squamosa seedlings under 50% shading is recommended as it resulted in higher degree-day accumulation and lower phyllochron for leaf emergence. [ABSTRACT FROM AUTHOR]

Camelina sativa (L.) is known as an important oilseed crop due to its application for biofuels, bio-products, and healthy food uses. However, it has a small seed (~ 0.7 × 1.5 mm), which can be a serious problem for plant establishment in some environments. Despite this, there is not enough information about this plant in response to edaphic (i.e., soil pH and burial depth) and abiotic environmental (i.e., temperature, water potential, salinity and light) factors. Our findings showed that all studied germination and emergence characteristics were affected by each of the environmental factors mentioned above. The cardinal temperatures were 1.50, 20.3 and 34.7 °C for the base, optimum and ceiling temperatures, respectively. The tolerance threshold values for salt and water potential stresses were 232 mM and − 1.29 MPa for seed germination, and 202 mM and − 0.75 MPa for the seedling emergence, respectively. There was no significant difference between the seeds germinated in the light and dark regimes. The maximum germination and seedling emergence were recorded at a pH range of 7–8 and a sowing depth of 0.5 cm. The results obtained in the present study could help camelina producers to effectively manage the production of this oilseed crop under stressful conditions. The models fitted here could be applied in simulating camelina growth. [ABSTRACT FROM AUTHOR]

Cedrela odorata is a native tree of economic importance, as its wood is highly demanded in the international market. In this work, the current and future distributions of C. odorata in Mexico under climate change scenarios were analyzed according to their optimal temperature ranges for seed germination. For the present distribution, 256 localities of the species' presence were obtained from the Global Biodiversity Information Facility (GBIF) database and modelled with MaxEnt. For the potential distribution, the National Center for Atmospheric Research model (CCSM4) was used under conservative and drastic scenarios (RCP2.6 and RCP8.5 Watts/m2, respectively) for the intermediate future (2050) and far future (2070). Potential distribution models were built from occurrence data within the optimum germination temperature range of the species. The potential distribution expanded by 5 and 7.8% in the intermediate and far future, respectively, compared with the current distribution. With the increase in temperature, adequate environmental conditions for the species distribution should be met in the central Mexican state of Guanajuato. The states of Chihuahua, Mexico, Morelos, Guerrero, and Durango presented a negative trend in potential distribution. Additionally, in the far future, the state of Chihuahua it is likely to not have adequate conditions for the presence of the species. For the prediction of the models, the precipitation variable during the driest month presented the greatest contribution. When the humidity is not limiting, the thermal climatic variables are the most important ones. Models based on its thermal niche for seed germination allowed for the identification of areas where temperature will positively affect seed germination, which will help maximize the establishment of plant populations and adaptation to different climate change scenarios. [ABSTRACT FROM AUTHOR]

Industrial hemp (Cannabis sativa L.) as a grain and fiber crop is experiencing a resurgence in North America. Due to governmental prohibition, there has been limited information on regional agronomic production systems including basic information on seed germination. This study was initiated to provide basic information on the relationship between temperature and germination in hemp seed. Germination was measured at constant temperatures ranging from 3 to 42 °C. Cardinal temperatures were determined for two industrial oil crop hemp cultivars ('Georgina' and 'Victoria'). The optimal germination temperature indicated by a high mean germination percentage and rate was between 19 and 30 °C. Optimal (29.6 °C), base (3.4 °C) and ceiling (42.6 °C) temperatures were calculated from a linear regression of the germination rates to reach 50% germination for each temperature. The thermal time for 'Georgina' and 'Victoria' to reach 50% germination at suboptimal temperatures was 694 and 714 °C h, respectively. The osmotic and solid matrix-primed hemp seeds germinated faster than the untreated seeds, but the final germination percentages were not different. The primed seeds germinated faster at supraoptimal temperatures but did not impact final germination percentages in the thermally inhibited seeds. [ABSTRACT FROM AUTHOR]

To quantify both the possible impacts of temperature as well as salinity stress on the germination responses of three seed lots of maize (large flat (LF), large round (LR) and small (SM)) and also, to calculate the cardinal temperatures for these seed lots, a laboratory experiment was launched through using halotime and halothermal time models. The experiment was conducted under eight constant temperatures (5, 10, 15, 20, 25, 30, 35 and 40 °C) and at the following four levels of salinity (0, 50, 100 and 200 mM, as provided by NaCl). The salinity tolerance threshold was 230, 241 and 415 mM for LF, LR and SM seed lots. Small seed lot showed the highest germination tolerance to salinity stress when comparison is made to others, thus providing the indication that under soil salinity conditions, germination and optimal seed placement in the field could be affected by various indicators including seed vigor as well as seed size. The salinity threshold amount was decreased linearly by the rise of temperature in all seed lots; so thermoinhibition could be introduced as a compatible approach in stressful situations. For LF, LR and SM seed lots, the cardinal temperatures at 0 mM were estimated to be 10, 9.7 and 8.5 °C for base, 33, 34 and 30 °C for optimum, and 44.6, 44.8 and 46.6 °C for the ceiling temperature, respectively. As a result, the applied models in this survey could accurately predict the germination responses of maize seeds with different shapes and sizes at different temperatures as well as salinity levels. [ABSTRACT FROM AUTHOR]

Seed germination (SG) is crucial for the survival of plant species; however, it is often subjected to unpredictable environmental conditions such as temperature (T) and salinity. Therefore, the objectives of this work were to concurrently investigate salinity and T effects on SG behavior of green bean using a halothermal time (HaloTT) model, to compute the cardinal Ts, and to explore the effect of salinity on seeds' salt ion assimilation (i.e., Na+ and Cl−). Our findings revealed that the effect of salt stress on SG was quantified well by the HaloTT model (R2 > 0.82). The estimated cardinal Ts at 0 mM were 8.15, 30.0, and 39 °C for the base (Tb), optimum (To), and ceiling (Tc) temperatures, respectively. The median threshold NaCl concentration (NaClb(50)) was 305 mM at To, then declined linearly at Ts ≥ To, reaching 0 mM at Tc. Decreasing germination capability at Ts above To was due to the shifts in NaClb(50), which appears as a thermoinhibition phenomenon. Na+ and Cl− assimilation enhanced significantly with T and seed ψ decreased compared to control. In conclusion, green bean SG was initially controlled by salt osmotic effect (≤ 150 mM), when exceeding this concentration, its effect became both osmotic and toxic. [ABSTRACT FROM AUTHOR]

Seed germination is one of the most critical plant growth stages regulated by temperature (T) and water potential (Ψ). This experiment was conducted to quantify the seed germination response of two quinoa (Chenopodium quinoa) cultivars (Sajama and Titicaca) to T and Ψ using hydro time (HT) and hydrothermal time (HTT) models. The results showed that T, Ψ, and their interaction significantly affected the maximum germination percentage (MGP) of both cultivars. Based on the results of the segmented model fit at Ψ = 0 MPa, the minimum ( T b ), optimum ( T o ), and maximum T ( T c ) in Sajama was estimated at 6.9, 21.9 and 34.9 °C, respectively and in Titicaca were estimated 8.0, 21.8 and 33.6 °C, respectively. While using the HTT model at different T and ѱ the T b was estimated by 8.28 and 8.39 °C for Sajama and Titicaca, respectively, the T o also estimated 26.96 for Sajama and 27.21 °C for Titicaca. Also, using the modified HTT model, the T o estimated 27.46 for Sajama and 27.31 °C for Titicaca. There was an increase in hydro time constant ( θ H ) when T increased at supra-optimal Ts (from 17 to 70 MPa h−1) as well as when the T decreased at sub-optimal Ts (from 17 to 79 MPa h−1). Also, it was observed that change of the T from T o to T b and T c increased base Ψ (ψb) so that for each degree Celsius decrease of T at sub-optimal Ts, the ψb increased by 0.032 and 0.034 MPa in Sajama and Titicaca, respectively. Each degree Celsius increase of T at supra-optimal Ts also increased ψb by 0.021 MPa in Sajama and 0.020 MPa in Titicaca. Using HT and HTT to predict germination rate for the 50% of germination (GR50) revealed that they had acceptable accuracy (HT, R2 = 0.97, and = 0.99 for Sajama and Titicaca, respectively; HTT, R2 = 0.87 for Sajama and = 0.90 for Titicaca). The results of this experiment provide data for future simulating models of quinoa growth and development. [ABSTRACT FROM AUTHOR]

Germination models are really useful in predicting seed germination, attributed to their application in economic crop management. Hence, we evaluated cardinal temperatures (Ts), seed germination behavior, and model coefficients of fenugreek under varying temperatures (Ts; 10, 20, 30, and 40 °C) and water potentials (ψs 0, −0.01, −0.02, and −0.05 MPa). We observed that the maximum and minimum hydrotime constant (θH) values at 20 °C, respectively. The base water potential at 50 percentiles (Ψb 50) exhibited an asymmetrical pattern with the highest (−0.9 MPa) value computed at 40 °C and the lowest (−0.13 MPa) at 10 °C. Furthermore, the ceiling temperature (TC), base temperature (Tb), and optimal temperature (To) of Fenugreek were determined to be 34.5 °C, 7.8 °C, and 18 °C, respectively. In addition, we observed that germination index, germination rate index, germination percentage, germination energy, Timson germination index, seed vigor index I and II, and root-shoot ratio are at their highest values at 20 °C and lowest at −0.05 MPa at 40 °C. Based on our findings, we suggest that the hydrothermal time model (HTT) can be used to explore the independent and synergistic effects of both T and ψ on the germination of seeds in different environmental conditions. The obtained model coefficients indicate that fenugreek is temperature-sensitive and suitable for agriculture in irrigated regions. [ABSTRACT FROM AUTHOR]

Germination of castor seeds of seven dwarf hybrid genotypes, compared to a ‘Local’ genotype, selected from a Tunisian population by the University of Catania well adapted to the Mediterranean environment, were studied at six different temperatures (8, 12, 16, 25, 32, and 40 °C). The results indicate that the optimal temperature (25 °C) and near-optimal temperature (32 °C) are the best temperatures for ensuring castor germination (final germination percentage (FGP) ≥ 82.81%). Furthermore, these temperatures positively influenced the vigour index (VI) and the radicle elongation. At a temperature of 8 °C, no germination occurred, while temperatures of 12 and 40 °C negatively affected the seed germination, which, in some genotypes, was null or negligible (Tb) 12.1 °C), could be used in the early sowing in spring.

Wheat is the most extensively cultivated crop and occupies a central place in human nutrition providing 20% of the daily food calories. This study was conducted to find both T and ψ effects on wheat germination and the cardinal Ts value; a lab experiment was accomplished using HTT models. Cultivars were germinated under different accelerated aging periods (AAP, 0, 24, 48, and 72 h) at each of the following constant Ts of 15, 20, 25, 30, and 35 °C at each of the ψs of 0, −0.05, −0.1, −0.15, and −0.2 MPa. GR, GP, and other germination parameters (GI, GRI, CVG, SVI-I, SVI-II, GE, and MGT) were significantly determined by solute potential, temperature, and reciprocal action in both cultivars (p ≤ 0.01). Depending on the confidence interval of the model co-efficiently between cultivars, there was no significant difference. Hence, the average of cardinal Ts was 15, 20, and 35 °C for the Tb, To, and Tc, respectively, in the control condition (0 MPa). Hydro-time values declined when Ts was raised to To in cultivars, then remained constant at Ts ≥ To (2.4 MPah−1 in Pirsabak 15 and 0.96 MPah−1 in Shahkar). The slope of the relationship between ψb(50) and TTsupra with temperature when Ts is raised above To and reaches 0 at Tc. In conclusion, the assessed parameter values in this study can easily be used in simulation models of wheat germination to quantitatively characterize the physiological status of wheat seed populations at different Ts and ψs. [ABSTRACT FROM AUTHOR]

Introduction One of the most important stages in the life cycle is germination, which is controlled by various environmental and genetic factors. Temperature and water potential are the most important factors in germination control. Different models for quantization of germination response to temperature and osmotic potential have been used. Quantification of germination response to osmotic potential and temperature is possible using non-liner regression models. Therefore, this research was carried out to determine the cardinal temperature of germination (base temperature, optimum and maximum germination) of safflower of Sofeh cultivar under different osmotic stress (drought stress) conditions and seed deterioration. Material and methods In this study germination response to water potential in different temperature were studied. Treatments included osmotic levels (0, -0.4 and -0.8 MPa), temperature (5, 10, 15, 20, 30, 35 and 40 °C) and seed deterioration (0 and 5 days). Ccumulative germination response of seeds to differential water potential and temperature were quantified using three-parameter sigmoidal model. For quantifying response of germination rate to temperature for different osmotic potential were used of 3 non-linear regression models (segmented, dent-like and beta). The root mean square of errors (RMSE), coefficient of determination (R2), CV and SE for relationship between the observed and the predicted germination percentage were used to select the superior model from among the employed methods. Germination percentage and time to 50% maximum seed germination of safflower were calculated for the different temperatures and osmotic potential by fitting 3-parameter sigmoidal functions to cumulative germination data. Results Results indicated that temperature in addition to germination percentage also on germination rate was effective. Also results showed that germination percentage and germination rate increased with increasing temperature, while germination percentage and germination rate reduced as a result of water potential increment. Results indicated that under different osmotic potential as 0, -0.4 and -0.8 MPa, the segmented model estimated base temperature as 2.23, 3.67 and 4.33 °C, the dent model estimated base temperature as 3, 3.96 and 4.33 °C, the beta model estimated base temperature as -1.22, -1.28 and -2.28 °C, the segmented model estimated optimum temperature as 23.05, 25.44 and 24.19 °C, the optimum temperature using beta model as 28.89, 28.99 and 26.46 °C, the dent-like model estimated lower limit of optimum temperature and upper limit of optimum temperature as 21.12, 21.92 and 20.16 and 30.07, 25 and 23.27 °C, ceiling temperature using segmented model were 40, 40 and 35 °C, using dent-like model were 40, 39.83 and 35 °C, using beta model were 40, 35 and 34.82 °C, the segmented model estimated fo as 23.02, 69.51 and 84.17 h, the dent-like model estimated as 27, 75.99 and 83.87 h and using beta model were 26.09, 75.09 and 103.41 h, respectively. In compared 3 models according to the root mean square of errors (RMSE) of germination time, the coefficient of determination (R2), CV and SE the best model for determination of cardinal temperatures of seed control of safflower for 0 MPa was dent-like model and for -0.4 and -0.8 MPa was segmented model and for seed deterioration of safflower in all osmotic potential was segmented model. In general, results indicated that lower limit of optimum temperature and upper limit of optimum temperature and ceiling temperature reduced but fo increased as a result of water potential increment. Conclusion Germination of safflower response to different temperatures and osmotic potentials, led to acceptable results. Utilizing the output of non-liner models at different temperatures can be useful in prediction of germination rate in different water potential.

Temperature is the main factor that impacts germination and therefore the success of annual crops, such as chia (Salvia hispanica L.), whose seeds are known for their high nutritional value related to its oil. The effect of temperature on germination is related to cardinal-temperature concepts that describe the range of temperature over which seeds of a particular species can germinate. Therefore, in this study, in addition to calculated germinative parameters such as total germination and germination rate of S. hispanica seeds, the effectiveness of non-linear models for estimating the cardinal temperatures of chia seeds was also determined. We observed that germination of S. hispanica occurred in cold to moderate-high temperatures (10–35 °C), having an optimal range between 25 and 35 °C, with the highest GR and t50 at 30 °C. Temperatures higher than 35 °C significantly reduced germination. Output parameters of the different non-linear models showed that the response of chia germination to temperature was best explained by beta models (B). Cardinal temperatures calculated by the B1 model for chia germination were: 2.52 ± 6.82 °C for the base, 30.45 ± 0.32 °C for the optimum, and 48.58 ± 2.93 °C for the ceiling temperature. [ABSTRACT FROM AUTHOR]

Abstract The objective of this work was to deter mine the base temperatures, thermal time requirements, and length of the main reproductive growth stages of acai palm (Euterpe oleracea) in the northeast of the state of Pará, in eastern Amazon, Brazil. The experiment was carried out from 2017 to 2019 in a 10 ha acai plantation, using the time-series analysis. Plant phenology was monitored weekly, and local weather conditions were monitored daily. The lower and upper base temperatures were of 12.92 and 32.46°C, respectively, for pre-flowering; 13.50 and 32.23°C for flowering; 12.14 and 32.55°C for green fruit stage; 11.64 and 32.78°C for fruit color-changing stage; and 11.23 and 32.94°C for maturation. The thermal time requirement and the average cycle length for the ideal harvest time of acai palm were 3,893.15 degree-days and 283 days, respectively. The thermal time requirement and the duration of the reproductive growth stage for acai palm are influenced by the period of the year and the variability of air temperature, which, when high, reduces the cycle of the crop, and when mild, increases it.

• The Population-based model describes well Parrotia persica germination behavior. • Population thermal parameters had changed during dormancy decreasing. • Seed dormancy of Parrotia persica is Type 3 of non-deep physiological. • A period of after-ripening followed by gibberellic acid suggests to break dormancy. Information regarding germination and dormancy of Parrotia persica seeds is limited and there is no report on cardinal temperatures and germination modeling of this tree species. Thus, the main aims of this study were to model dormancy and germination of P. persica seeds and to identify the best way(s) to overcome seed dormancy in this species. Freshly matured seeds had spatulate, fully developed embryos (FA1 type) and the seed coat was water permeable. Fresh seeds germinated less than 20% at 5–30 °C, and gibberellic acid (GA) increased germination to about 40% at 5–30 °C, peaking at 53% at at 20 °C. Population thermal parameters (T l and T h) had changed among dormancy breaking treatments. After-ripened seeds and those treated with GA had the lowest lower limit (T l) and the highest higher limit temperatures which were 0.0 and 37 °C, respectively. The highest T l and the lowest T h were observed in freshly matured seeds without any treatments (Control-MT) which were 24 and 26 °C; the narrowest temperature range for germination, implying the highest seed dormancy. Base (T b) and ceiling (T c) temperatures for the final germination percentage of non-dormant seeds were 0, and 40°C. Cardinal temperatures for the rate (speed) of germination of non-dormant seeds were almost the same as the observed values for final germination percentage. Seeds of P. persica must have Type 3 of non-deep physiological dormancy based on the graphical method, since T b decreased and T c increased as dormancy breaking progresses in a population. Population thermal parameters (T l and T h) also showed the same change in different dormancy breaking treatments in which dormant seeds had higher T l and lower T h than non-dormant seeds (after-ripened plus GA). For commercial usage or conservation projects, it is suggested to use a period of after-ripening followed by GA treatment to break dormancy. [ABSTRACT FROM AUTHOR]

Ambient temperatures are major factors regulating the growth rates, yields, and geographical distribution of crop species. The cultivation of sesame (Sesamum indicum L.) is expanding with the rising demand in regions where it is not traditionally grown, and sub-optimal yields due to extremely low or high temperatures could occur. Currently literature lacks information on the temperature responses of sesame growth. An experiment was conducted to quantify the effects of different temperatures on vegetative growth and reproductive development of sesame, and to estimate its cardinal temperature limits (Topt; Tmin; Tmax). Plants were subjected to six different day/night temperature treatments of 40/32, 36/28, 32/24, 28/20, and 20/12 °C using walk-in growth chambers. Vegetative growth of sesame was sensitive to low temperatures (< 15 °C), but tolerant of high temperatures. The cardinal temperature limits of 15.7 °C (Tmin), 27.3 °C (Topt), and 44.6 °C (Tmax) were observed for rate of biomass accumulation. Sesame reached the flowering stage under moderate to high temperature conditions; however, reproductive yields progressively declined above 25 °C, and no seed yields were obtained beyond 33 °C. The estimated temperature limits could be employed to develop crop models for simulating management and adaptation strategies of sesame under current and future climate scenarios, and adaptation to regions where the crop is not currently grown. Future research should focus on understanding factors controlling the temperature tolerance of reproductive development in sesame, to provide a broader geographical adaptation. [ABSTRACT FROM AUTHOR]

Macrophomina phaseolina is a soil born fungal pathogen causing charcoal rot of soybean and several other plants. Disease intensity in different hosts is related to hot and dry weather condition. In order to determination of cardinal (minimum, optimum and maximum) temperatures required for mycelial growth and microsclerotial germination, three fungal isolates from soybean fields of three regions Aliabad, Gorgan and Kalaleh in Golestan province were studied in vitro. Mycelial growth and germinated microsclerotia number were recorded daily in different temperatures and data were fitted with three growth models (Beta, segmented and dent-like). Results of statistical analyses (nonlinear regression) showed that the segmented and Beta were the most suitable model for describing the relationships between mycelial growth and microsclerotial germination of this fungus, respectively. Minimum, optimum and maximum temperatures estimated for mycelial growth were 8, 34.5 and 44.3 ºC, respectively, and 8.9, 32.3 and 45.5 ºC for microsclerotial germination. [ABSTRACT FROM AUTHOR]

Pathogen life history traits influence epidemic development and pathogen adaptive ability to interact with their hosts in different environments. Reduced traits variation may compromise pathogen evolutionary potential, which is particularly important for introduced pathogens. Fusarium circinatum (cause of pine pitch canker) is an invasive fungal pathogen in Europe, with current distribution restricted to forest stands of Pinus radiata and Pinus pinaster in northern Spain and Portugal. This study aimed to quantify pathogenic traits of Spanish isolates of F. circinatum, with two of the strains representing the two dominant haplotypes in the Spanish population. Disease severity was measured on P. radiata, analyzing the influence of temperature and moisture duration on infection as well as the influence of temperature on spore germination, sporulation, and mycelial growth. Results indicated that the isolate representing the most common haplotype caused more severe disease on P. radiata at 25 and 30°C compared with the second most common haplotype but caused less severe disease at 15°C. Spore germination was higher for the most common haplotype, which produced more spores at 20 and 25°C. The isolate showed hyphal melanization at 5°C, which has been associated with survival and may be important because no resting structures have been described for F. circinatum. Our study determined that longer moisture periods during infection result in more severe disease from 7 to 24 h, regardless of the isolate virulence. This is the first study on virulence of the most abundant haplotypes of F. circinatum in Spain as affected by temperatures and moisture. [ABSTRACT FROM AUTHOR]

DOR: 98.1000/2383-1251.1398. 6.111.12.2.1603.1610 Extended abstract Introduction: Temperature is one of the primary environmental regulators of seed germination. Seed priming technique has been known as a challenge to improving germination and seedling emergence under different environmental stresses. Quantification of germination response to temperature and priming is possible, using non-liner regression models. Therefore, the objective of this study was to evaluate the effect of temperature and priming on germination and determination of cardinal temperatures (base, optimum and maximum) of Brassica napus L. Material and Methods: Treatments included priming levels (non-priming, priming with water, gibberellin 50 and 100 mg/l) and temperature (5, 10, 15, 20, 30, 35 and 40 °C). Germination percentage and time to 50% maximum seed germination of Brassica napus L. were calculated for different temperatures and priming by fitting 3-parameter logistic functions to cumulative germination data. For the purpose of quantifying the response of germination rate to temperature, use was made of 3 nonlinear regression models (segmented, dent-like and beta). The root mean square of errors (RMSE), coefficient of determination (R2), CV and SE for the relationship between the observed and the predicted germination percentage were used to compare the models and select the superior model from among the methods employed. Results: The results indicated that temperature and priming were effective in both germination percentage and germination rate. In addition, the results showed that germination percentage and rate increase with increasing temperature to the optimum level and using priming. As for the comparison of the 3 models, according to the root mean square of errors (RMSE) of germination time, the coefficient of determination (R2), CV and SE, the best model for the determination of cardinal temperatures of Brassica napus L. for non-primed seeds was the segmented model. For hydro-priming and hormone-priming with 50 mg/l GA, the best models were segmented and dent-like models and for hormone-priming with 100 mg/l GA, the dent-like model was the best. The results showed that for non-priming, hydropriming with water, gibberellin 50 and 100 mg/l treatments, the segmented model estimated base temperature as 3.54, 2.57, 2.34 and 2.34 °C and dent-model estimated base temperature as 3.34, 2.45, 2.21 and 2.83 °C, respectively. The segmented model estimated optimum temperature as 24.62, 23.23, 23.69 and 24.38 °C. The dent-model estimated lower limit of optimum temperature and upper limit of optimum temperature as 20.01, 19.62, 16.25, 19.87 and 28.81, 27.38, 29.58 and 27.31 °C. Conclusion: Utilizing non-liner models (segmented, dent-like and beta) for quantification of germination of Brassica napus L. response to different temperatures and priming produced desirable results. Therefore, utilizing the output of these models at different temperatures can be useful in the prediction of germination rate in different treatments. Highlights: 1-The effect of priming on germination of Brassica napuswas investigated. 2-The temperature range of rapeseed germination of Brassica napus changes with the use of seed priming.

Abstract This study aims to explore the effect of environmental factors (temperature, light, storage time) on germination response and dormancy patterns in eight Mediterranean native wildplants, belonging to the Euphorbia L. genus. In detail, we considered E. amygdaloides subsp. arbuscula, E. bivonae subsp. bivonae, E. ceratocarpa, E. characias, E. dendroides, E. melapetala, E. myrsinites, and E. rigida. We collected seeds from natural plant populations and performed germination assays in climatic chambers at seven constant temperatures (from 5 to 35°C, with 5°C increments), and four fluctuating temperature regimes (8/15, 8/20, 8/25, and 8/30°C, with a 12/12 hr thermoperiod). Germination assays were set up both in dark (D) and in light/dark conditions (L/D, 12/12 hr photoperiod), after short and long seed storage (SS around 30 days and LS around 150 days). For all these species, except E. amygdaloides subsp. arbuscula, results show that the final germinated proportions were improved by a long storage period (>150 days), which supports the existence of nondeep physiological dormancy. Optimal temperature levels ranged from 14.3 to 21.3°C and base temperatures ranged from 5.6 to 12.1°C, while ceiling temperatures from 25.6 to 34.7°C. For none of these species, germinations were favored by an alternating daily temperature regime, while in several instances, germinations were quicker and more complete in darkness, than in an alternating light/dark regime. In some instances, extreme temperature levels (5 and 30°C) induced dormancy and germinations did not resume when seeds were exposed at optimal temperature levels. Results are discussed in terms of the dynamics of emergences and how this might be affected by climate changes.

Cedrela odorata is a native tree of economic importance, as its wood is highly demanded in the international market. In this work, the current and future distributions of C. odorata in Mexico under climate change scenarios were analyzed according to their optimal temperature ranges for seed germination. For the present distribution, 256 localities of the species’ presence were obtained from the Global Biodiversity Information Facility (GBIF) database and modelled with MaxEnt. For the potential distribution, the National Center for Atmospheric Research model (CCSM4) was used under conservative and drastic scenarios (RCP2.6 and RCP8.5 Watts/m2, respectively) for the intermediate future (2050) and far future (2070). Potential distribution models were built from occurrence data within the optimum germination temperature range of the species. The potential distribution expanded by 5 and 7.8% in the intermediate and far future, respectively, compared with the current distribution. With the increase in temperature, adequate environmental conditions for the species distribution should be met in the central Mexican state of Guanajuato. The states of Chihuahua, Mexico, Morelos, Guerrero, and Durango presented a negative trend in potential distribution. Additionally, in the far future, the state of Chihuahua it is likely to not have adequate conditions for the presence of the species. For the prediction of the models, the precipitation variable during the driest month presented the greatest contribution. When the humidity is not limiting, the thermal climatic variables are the most important ones. Models based on its thermal niche for seed germination allowed for the identification of areas where temperature will positively affect seed germination, which will help maximize the establishment of plant populations and adaptation to different climate change scenarios.

Seed germination is regulated by temperature and can thus be quantified by thermal models, which can predict germination occurrence in biomes and plant survival under possible climate change scenarios. The objective of this study was to quantify germination based on thermal time and survival risk of 14 species in the Brazilian Cerrado in scenarios of future climate change. Seeds were collected in the warmer regions of the Cerrado, central Brazil, placed in incubators to germinate at constant temperatures of 10–50°C and evaluated every hour or day. Germination rate (R50), time for germination of 50% of the seeds (T50) and dent-like function were used to determine cardinal temperatures. Thermal time parameters were estimated using the Weibull model. Seed germination forecasts were made based on the International Panel on Climatic Change (IPCC) scenarios of global temperature increase. Base temperatures (Tb) ranged from 3.5 to 16.5°C, maximum temperatures (Tmax) from 35 to 50°C and optimum temperatures (To) from 30 to 35°C. Estimated thermal time varied from 484°C h to 400°C d at sub-optimal temperatures and 108°C h at 126°C d at supra-optimal temperatures. Species more distributed showed a higher thermal range of germination and are less susceptible to extinction in temperature increase scenarios. The results of this study suggest that seeds that are non-dormant after dispersal may be the most vulnerable in the future. In this context, our predictions contribute to understand how the survival of trees and shrubs will be affected in the Cerrado in the future. [ABSTRACT FROM AUTHOR]

Defining the cardinal temperatures for germination in the scenario of climate change with prediction of an increased terrestrial temperature plays an important role in conserving plant resources. This study aimed to define the cardinal temperatures, the time of conducting germination tests, and to apply the thermal time model for seeds of Diospyros inconstans. Thermal screening was carried out, based on germination tests performed in BOD chambers, at constant temperatures of 10, 20, 25, 30 and 40 °C, under a photoperiod of 12 hours/light. The cardinal temperatures for germination of D. inconstans seeds are 26.7 °C (optimal temperature), 13.8 °C (minimum temperature) and 37.7 °C (maximum temperature). Germination tests for the species can be conducted at optimum temperature, lasting 26 days for radicle emission and 63 days for formation of normal seedlings. [ABSTRACT FROM AUTHOR]

The species' germination response evolves based on its population environment; therefore, the responses of each local population evolve independently. We investigated two xeric species from central Mexico, Echeveria gibbiflora and Penstemon campanulatus, the populations of which inhabit two localities (Reserva Ecológica del Pedregal de San Ángel [REPSA] and Parque Ecológico de la Ciudad de México [PECM]) that differ in environmental conditions. For both species and populations, final germination, cardinal temperatures, thermal time and range of temperature for germination (RTG) were determined in seeds that were (a) collected recently, (b) stored in a laboratory for 2 months and (c) reciprocally buried in field conditions for 2 months. The results indicated that for both species, seed population, laboratory storage and temperature were significant for final germination. These responses indicated differences in germination based primarily on the site in P. campanulatus (PECM seeds germinated at higher percentages than REPSA seeds) and the burial site in the REPSA seeds of E. gibbiflora. Cluster and discriminant analyses were conducted for both species, identifying the following significant variables for group treatments: base temperature between the stored and buried seeds of E. gibbiflora and the ceiling temperature between the recently collected, stored and buried seeds of P. campanulatus. The results suggest that instead of seed population, burial (in both species) and laboratory storage (in P. campanulatus) narrowed the RTG. These responses could indicate plasticity in both germination and dormancy in response to environmental conditions experienced in the different habitats, which are crucial for understanding species' adaptive capacity. [ABSTRACT FROM AUTHOR]

Temperature is the main factor that impacts germination and therefore the success of annual crops, such as chia (Salvia hispanica L.), whose seeds are known for their high nutritional value related to its oil. The effect of temperature on germination is related to cardinal-temperature concepts that describe the range of temperature over which seeds of a particular species can germinate. Therefore, in this study, in addition to calculated germinative parameters such as total germination and germination rate of S. hispanica seeds, the effectiveness of non-linear models for estimating the cardinal temperatures of chia seeds was also determined. We observed that germination of S. hispanica occurred in cold to moderate-high temperatures (10–35 °C), having an optimal range between 25 and 35 °C, with the highest GR and t50 at 30 °C. Temperatures higher than 35 °C significantly reduced germination. Output parameters of the different non-linear models showed that the response of chia germination to temperature was best explained by beta models (B). Cardinal temperatures calculated by the B1 model for chia germination were: 2.52 ± 6.82 °C for the base, 30.45 ± 0.32 °C for the optimum, and 48.58 ± 2.93 °C for the ceiling temperature.

Introduction Seed germination is a complex biological process that is influenced by various environmental and genetic factors. Temperature and water potential are two primary environmental regulators of seed germination. Quantification of germination response to osmotic potential and temperature is possible using non-liner regression models. Tall mallow (Malva sylvestris) is an important invasive weed in southwest Iran and also a medicinal plant. ). Tall mallow is native home in Western Europe, North Africa and Asia. This plant frequently found in cultivated fields, orchards, gardens, farmyards near manure piles, along roadsides, in towns, and in waste places and, can grow anywhere from 60 to 120 cm in length. Not published information exists concerning effect of osmotic potential on cardinal temperatures, Therefore, the objective of this research was to evaluate the effect of osmotic potential and different temperatures on germination and determination cardinal temperatures (base, optimum and maximum) of Malva sylvestris under osmotic stress. Material and methods In this study germination response to water potential in different temperature were studied. Treatments included osmotic levels (0, -0.2, -0.4, -0.6 and -0.8 MPa) and temperature (5, 10, 15, 20, 30, 35 and 40 °C). Cumulative germination response of seeds to differential water potential and temperature were quantified using three-parameter sigmoidal model. For quantifying response of germination rate to temperature for different osmotic potential were used of 3 non-linear regression models (segmented, dent-like and beta). The root mean square of errors (RMSE), coefficient of determination (R2), CV and SE for relationship between the observed and the predicted germination percentage were used to select the superior model from among the employed methods. Germination percentage and time to 50% maximum seed germination of Malva sylvestris were calculated for the different temperatures and osmotic potential by fitting 3-parameter sigmoidal functions to cumulative germination data. Results Results indicated that temperature in addition to germination percentage also on germination rate was effective. Also results showed that germination percentage and germination rate increased with increasing temperature, while germination percentage and germination rate reduced as a result of water potential increment. Results indicated that under different osmotic potential as 0, -0.2, -0.4, -0.6 and -0.8 MPa, the segmented model estimated base temperature as 1.46, 1.82, 1.29, 0.43 and 4.06 °C, the dent model estimated base temperature as 1.23, 1.82, 3.04, 2.63 and 4.07 °C, the beta model estimated base temperature as -4.32, 4.46, 1.86, 1.61 and 4.13 °C, the segmented model estimated optimum temperature as 28.29, 27.58, 22.24, 22.51 and19.69 °C, the optimum temperature using beta model as 27.89, 25.41, 23.18 and 21.05 °C, the dent-like model estimated lower limit of optimum temperature and upper limit of optimum temperature as 23.16 and 33.58, 16.86 and 30, 16.1 and 25, 15.81 and 25, 19.51 and 1987 °C, ceiling temperature using segmented model were 42.9, 40, 40, 40 and 34.96 °C, using dent-like model were 42, 40, 40, 40 and 34.96 °C, using beta model were 42.01, 40.02, 39.96, 39.98 and 34.83 °C, the segmented model estimated fo as 13.87, 18.45, 19.43, 25.24 and 36.13 h, the dent-like model estimated as 16.65, 23.28, 23.43, 30.48 and 36.56 h and using beta model were 16.06, 21.34, 22.21, 28.92 and 42.89 h, respectively. In compared 3 models according to the root mean square of errors (RMSE) of germination time, the coefficient of determination (R2), CV and SE the best model for determination of cardinal temperatures of Malva sylvestris for 0 to -0.6 MPa was dent-like model and for -0.8 MPa was segmented model. In general, results indicated that lower limit of optimum temperature and upper limit of optimum temperature and ceiling temperature reduced but fo increased as a result of water potential increment. Conclusion Germination of Malva sylvestris response to different temperatures and osmotic potentials, led to acceptable results. Utilizing the output of non-liner models at different temperatures can be useful in prediction of germination rate in different water potential.

Seed germination is the first developmental phase in a plant's life cycle that is followed by emergence from the soil, successful seedling and establishment, and fruitful yield. Seed germination is influenced by multiple environmental factors such as temperature, moisture, and aeration. An in vitro experiment was conducted to quantify the effects of temperatures ranging from 10°C to 42.5°C on germination properties of corn, cotton, and soybean seeds. Cumulative seed germination was recorded over time, was fitted with a three-parameter sigmoidal function to calculate maximum seed germination and seed germination rate. Maximum seed germination was significantly influenced by the interaction of temperature and species. The seed germination rate was further analyzed as a function of temperature by fitting bilinear and quadratic functions to the data. Cardinal temperatures (minimum, optimum, and maximum) were estimated from that regression analysis. Corn displayed the highest optimal temperature of 34.6°C. Cotton showed higher minimum and maximum cardinal temperatures than both corn and soybean. The cardinal temperatures and functional relationships between seed germination rate and temperature determined in this experiment will be useful to update crop simulation models and assess the best planting dates for rapid, successful germination based on environmental conditions. [ABSTRACT FROM AUTHOR]

Recognition of Eryngium caeruleum germination biology can provide the possibility of forecasting the seed dormancy and germination level in various conditions. This study was conducted as factorial experiment based on completely randomized design with three replications in the laboratory of Agronomy and Plant Breeding Department, College of Agriculture and Natural Resources, University of Tehran, to understand Eryngium caeruleum seed dormancy and response of germination thermal parameters. The experimental factors were included three levels of gibberellic acid (0, 250, 500 mg/l), six chilling time (1, 3, 5, 10, 15, 30 days) and seven temperatures (5, 10, 15, 20, 25, 30, 35°c). Germination parameters were obtained by the segmented model under the influence of gibberellic acid and chilling treatments. The results of this study showed that, the best treatment for reducing dormancy level, cardinal temperatures for germination including base, optimum and ceiling temperatures was obtained 1.81, 22.31, and 34.10°c respectively. Increasing of the chilling time and the gibberellic acid concentration from 0 to 250 mg/l, decreased the base temperature, and increased optimum temperature. Ceiling temperature, at first was increased and then decreased. [ABSTRACT FROM AUTHOR]

Understanding how plant species respond to temperature and salt stress is crucial for ensuring successful seed germination and crop production. The ongoing effects of global climate change, such as temperature fluctuations, can have serious consequences for seed germination. This study aimed to investigate the impact of salinity (NaCl) and temperature (T), individually and in interaction, on the germination responses of four North African pastoral grass species Stipagrostis (S. ciliata , S. pungens , S. obtusa , and S. pulmosa) and the potential impact of climate change scenarios on their seed germination. Significant effects of NaCl , T , and their interaction (NaCl × T) were observed on both germination percentage and germination rate across the four species. The halotime and halothermal time models successfully predicted germination time courses for the four species (R2 > 0.86). The base T (T b), optimum T (T o), and ceiling T (T c) were 13, 9.8, 9.0, and 10.7 °C; 25, 29, 28, and 27 °C; and 34, 35, 38, and 34 °C for S. ciliata , S. obtusa , S. pungens , and S. pulmosa , respectively. The predictions indicated that higher temperatures associated with climate change caused shorter germination times (i.e., 42 h for S. ciliata and 23–24 h for S. pulmosa , S. pungens , and S. obtusa) suggesting potential shifts in germination behavior in response to changing environmental conditions. Furthermore, the study assessed germination recovery after salt stress, revealing species-specific responses to both T and NaCl variations. The results highlighted the resilience of the studied grass species, as seeds were capable of recovering germination after exposure to salt stress. Therefore, the research provides comprehensive insights into the intricate relationships between T , NaCl , and germination in North African pastoral grasses. The findings contribute to our understanding of how these grasses may respond to changing environmental conditions, particularly under climate change scenarios. • Investigated NaCl and temperature (T) influence, individually and interactively, on germination of four North African grasses. • Significant effects of both stresses on germination percentage and rate. • Halotime and halothermal time models predicted well (R2 > 0.86) the seed germination. • Cardinal Ts were determined and predicted shorter germination times with higher temperatures were found. • Assessed germination recovery after salt stress highlighted the resilience of the grass species. [ABSTRACT FROM AUTHOR]

Population-based threshold models may aid in quantification of germination niches under stressful conditions such as salinity, temperature, and their interactions to understand seedling emergence patterns. Seeds of Sarcocornia fruticosa , Sarcocornia alpini , and Salicornia emerici were subjected to various temperatures at different NaCl concentrations. The median base NaCl concentration was roughly steady (0.68, 0.73, and 0.70 M, respectively) at sub-optimal temperatures, then decreased linearly at supra-optimal temperatures until the ceiling temperature. The estimated base, optimum and ceiling temperatures, in water, were –0.5, 15, and 29 °C for Sarcocornia fruticosa , –2.5, 11, and 24 °C for Sarcocornia alpini , and 9.5, 25, and 40 °C for Salicornia emerici , respectively. For all species, the base temperature did not change with the salinity, while both optimal and ceiling temperatures decreased. S. emerici showed rapid and synchronized germination when salinity decreased during the rainy season coinciding with favorable temperatures. • S. fruticosa , S. alpini , and S. emerici seeds were subjected to various temperatures at different NaCl concentrations. • The NaCl b(50) concentration was roughly steady at sub-optimal temperatures, then decreased linearly at supra-optimal ones. • T b , T o , and T c , in 0 M NaCl, were –0.5, 15, and 29°C for S. fruticosa , –2.5, 11, and 24°C for S. alpini , and 9.5, 25, and 40°C for S. emerici , respectively. • For all species, T b did not change with the salinity, while T o and T c decreased. • S. emerici showed rapid and synchronized germination when salinity decreased during the rainy season coinciding with favorable temperatures. [ABSTRACT FROM AUTHOR]

Barley (Hordeum vulgare L.) is a salt-tolerant crop with considerable economic value in salinity-affected arid and semiarid areas. In the laboratory experiment, the halothermal time (HaloTT) model was used to examine barley seed germination (SG) at six constant cardinal temperatures (Ts) of 15, 20, 25, 30, 35, and 40 °C under five different water potentials (ψs) of 0, −0.5, −1.5, −1.0, and −2.0 MPa. Results showed that at optimum moisture (0 MPa), the highest germination percentage (GP) was recorded at 20 °C and the lowest at 40 °C. Moreover, GP increased with the accelerated aging period (AAP) and significantly (p ≤ 0.05) decreased with high T. In addition, with a decrease of ψ from 0 to −0.5, −1, 1.5, and −2.0 MPa, GP decreased by 93.33, 76.67, 46.67, and 33.33%, respectively, in comparison with 0 MPa. The maximum halftime constant (θHalo) and coefficient of determination (R2) values were recorded at 20 °C and 30 °C, respectively. The optimum temperature (To) for barley is 20 °C, base Ψ of 50th percentile (Ψb (50)) is −0.23 Mpa, and standard deviation of Ψb (σΨb) is 0.21 MPa. The cardinal Ts for germination is 15 °C (Tb), 20 °C (To), and 40 °C (Tc). The GP, germination rate index (GRI), germination index (GI), coefficient of the velocity of germination (CVG), germination energy (GE), seed vigor index I and II (SVI-I & II), Timson germination index (GI), and root shoot ratio (RSR) were recorded maximum at 0 MPa at 20 °C and minimum at −2.0 MPa at 40 °C. Mean germination time (MGT) and time to 50% germination (T 50%) were maximum at −2 MPa at 40 °C, and minimum at 20 °C, respectively. In conclusion, the HaloTT model accurately predicted the germination time course of barley in response to T, Ψ, or NaCl. Therefore, barley can be regarded as a salt-tolerant plant and suitable for cultivation in arid and semi-arid regions due to its high resistance to salinity.

Safflower (Carthamustinctorius L.) is one of the oldest domesticated crops, mainly grown as an oilseed in the arid and semiarid regions of the world. This study was conducted to investigate the Cardinal temperatures and to identify the effects of occurrence of drought stress in maternal environment on seed germination aspects of some Carthamus species according to a completely randomized design in 2014. To accomplish this, seeds of 13 genotypes from C. tinctorius, C. palaestinus, C. oxyacanthus, C. glaucus and C. lanatus were used which had been harvested from plants grown at normal and drought stress conditions. Seeds were subjected to 9 fixed temperatures (5, 10, 15, 20, 25, 30, 35, 40 and 45°C) for germination in the growth chamber according to a factorial experiment. Results showed that the effects of genotype, species, temperature, pretreatment drought stress and some of their interactions were significant for certain germination characteristics at 0.05% probability level. Significant reductions occurred in the germination rate of seeds at temperatures below 10°C and above 30°C. Although there were significant differences in percent of seed germination among species, seeds harvested from drought stressed plants were not significantly different from the ones harvested from non-stressed plants in terms of cardinal temperatures. Hence, it is more likely that cardinal temperatures will not cause difficulties in the case of inter-specific breeding programs for drought tolerant safflower cultivar development.

Swietenia macrophylla is an economically important tree species propagated by seeds that lose their viability in a short time, making seed germination a key stage for the species recruitment. The objective of this study was to determine the cardinal temperatures and thermal time for seed germination of S. macrophylla; and its potential distribution under different climate change scenarios. Seeds were placed in germination chambers at constant temperatures from 5 to 45 °C and their thermal responses modelled using a thermal time approach. In addition, the potential biogeographic distribution was projected according to the Community Climate System Model version 4 (CCSM4). Germination rate reached its maximum at 37.3 ± 1.3 °C (To); seed germination decreased to near zero at 52.7 ± 2.2 °C (ceiling temperature, Tc) and at 12.8 ± 2.4 °C (base temperature, Tb). The suboptimal thermal time θ150 needed for 50% germination was ca. 190 °Cd, which in the current scenario is accumulated in 20 days. The CCSM4 model estimates an increase of the potential distribution of the species of 12.3 to 18.3% compared to the current scenario. The temperature had an important effect on the physiological processes of the seeds. With the increase in temperature, the thermal needs for germination are completed in less time, so the species will not be affected in its distribution. Although the distribution of the species may not be affected, it is crucial to generate sustainable management strategies to ensure its long-term conservation.

Eruca (Eruca sativa; Brassicaceae) is an important industrial crop due to its ability to grow under a wide range of climatic conditions and in poor fertility lands and also for the quality of seed oil and protein. Seed germination (SG) is an important event in plant's life history which can significantly be influenced by several environmental factors such as temperature (T), water potential (ψ), salinity, pH, and burial depth. Therefore, this study aimed (i) to investigate the effects of these environmental factors on SG behavior of Eruca using several mathematical models, (ii) to determine the cardinal Ts and tolerance threshold value for each trait (i.e., 50% reduction than its maximum value) affected by the environmental factor, and (iii) to quantify the response of Eruca seedling growth to each environmental factor. The results indicated that Eruca SG and seedling growth were significantly influenced by these factors (P < 0.05). The estimated cardinal Ts were 1 °C for the base T, 30 °C for the optimum T, and 40.8 °C for the ceiling T. The salt and drought tolerance threshold values were 257 mM NaCl and − 1.2 MPa for SG and 247 mM NaCl and − 1 MPa for the seedling growth, respectively, suggesting that the seedling growth was more sensitive than SG under both salt and drought stresses in Eruca. In addition, the maximum SG and seedling growth were observed at pH 7 and burial depth 1.9 cm. In general, the models used in this study could describe well the response of Eruca SG under different levels of environmental factors and also their parameters could easily be used in Eruca SG simulation models. This information also could help us to better manage the production of this plant under stressful conditions and/or to determine its geographic range expansion in the world. [ABSTRACT FROM AUTHOR]

Conyza bonariensis is one of the most problematic weed species throughout the world. It is considered highly noxious due to its interference with human activities, and especially the competition it poses with economically important crops. This research investigated the temperature requirements for seed germination of four populations of C. bonariensis with distinct origin and the influence of daily alternating temperatures. For this, a set of germination tests were performed in growth chambers to explore the effect of constant and alternating temperatures. Seeds of the four populations (from Lleida, Badajoz and Seville, Spain and Bahía Blanca, Argentina) were maintained at constant temperatures ranging from 5 to 35°C. The final germination and cardinal temperatures (base, optimum and maximum) of each population were obtained. We also tested the influence of daily alternating temperatures on final germination. To do so, seeds were exposed to two temperature regimes: 5/15, 10/20, 15/25, 20/30 and 25/35°C night/day temperature (intervals increasing 5°C, with constant oscillation of 10°C) and to 18/22, 16/24, 14/26, 12/28 and 10/30°C night/day temperature (intervals with average of 20°C, but increasing the oscillation in 4°C between intervals). In general, all populations behaved similarly, with the highest germination percentages occurring in the optimum temperature range (between 21.7°C and 22.3°C) for both constant and alternating temperatures. In general, climatic origin affected germination response, where seeds obtained from the coldest origin exhibited the highest germination percentage at the lowest temperature assayed. In addition, we observed that the alternating temperatures can positively affect total germination, especially in oscillations that were further from the average optimum temperature (20°C), with high germination percentage for the oscillations of 15/25, 20/30, 18/22, 16/24, 14/26, 12/28 and 10/30°C in all populations. The cardinal temperatures obtained were significantly different across the populations. These results provide information that will facilitate a better understanding of the behaviour of Conyza and improve current field emergence models. [ABSTRACT FROM AUTHOR]