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Extreme high-temperature stress (HTS) associated with climate change poses potential threats to wheat grain yield and quality. Wheat grain protein concentration (GPC) is a determinant of wheat quality for human nutrition and is often neglected in attempts to assess climate change impacts on wheat production. Crop models are useful tools for quantification of temperature impacts on grain yield and quality. Current crop models either cannot simulate or can simulate only partially the effects of HTS on crop N dynamics and grain N accumulation. There is a paucity of observational data on crop N and grain quality collected under systematic HTS scenarios to develop algorithms for model improvement as well as evaluate crop models. Two-year phytotron experiments were conducted with two wheat cultivars under HTS at anthesis, grain filling, and both stages. HTS significantly reduced total aboveground N and increased the rate of grain N accumulation, while total aboveground N and the rate of grain N accumulation were more sensitive to HTS at anthesis than at grain filling. The observed relationships between total aboveground N, rate of grain N accumulation, and HTS were quantified and incorporated into the WheatGrow model. The new HTS routines improved simulation of the dynamics of total aboveground N, grain N accumulation, and GPC by the model. The improved model provided better estimates of total aboveground N, grain N accumulation, and GPC under HTS (the normalized root mean square error was reduced by 40%, 85%, and 80%, respectively) than the original WheatGrow model. The improvements in the model enhance its applicability to the assessment of climate change effects on wheat grain quality by reducing the uncertainties of simulating N dynamics and grain quality under HTS.

A stable QTL qSalt-A04-1 for salt tolerance in the cotton seed germination stage, and two candidate genes, GhGASA1 and GhADC2, that play negative roles by modulating the GA and PA signalling pathways, respectively, were identified. The successful transition of a seed into a seedling is a prerequisite for plant propagation and crop yield. Germination is a vulnerable stage in a plant’s life cycle that is strongly affected by environmental conditions, such as salinity. In this study, we identified a novel quantitative trait locus (QTL) qRGR-A04-1 associated with the relative germination rate (RGR) after salt stress treatment based on a high-density genetic map under phytotron and field conditions, with LOD values that ranged from 6.65 to 16.83 and 6.11–12.63% phenotypic variations in all five environmental tests. Two candidate genes with significantly differential expression between the two parents were finally identified through RNA-seq and qRT-PCR analyses. Further functional analyses showed that GhGASA1- and GhADC2-overexpression lines were more sensitive to salt stress than wild-type Arabidopsis based on the regulation of the transcript levels of gibberellic acid (GA)- and polyamine (PA)- related genes in GA and PA biosynthesis and the reduction in the accumulation of GA and PA, respectively, under salt stress. Virus-induced gene silencing analysis showed that TRV:GASA1 and TRV:ADC2 were more tolerant to salt stress than TRV:00 based on the increased expression of GA synthesis genes and decreased H2O2 content, respectively. Taken together, our results suggested that QTL qRGR-A04-1 and its two harboured genes, GhGASA1 and GhADC2, are promising candidates for salt tolerance improvement in cotton.

Background Low growth temperatures and the special light qualities of midnight sun in northern Scandinavia, have both been shown to improve eating quality of swede root bulbs. To study the combined effect of these factors on root development and sensory-related compounds, plants were grown in phytotron under different 24 h supplemental light-emitting diode (LED) light colours, at constant 15 °C, or reduced end-of-season temperature at 9 °C. Results Far-red LED (740 nm) light induced longer leaves and produced more roundly shaped bulbs, than the other light quality treatments. At constant 15 °C, supplemental light of far-red LED also produced a stronger purple crown skin colour than the other LED treatments. This difference between light quality treatments disappeared at 9 °C, as all bulb crowns developed a purple colour. There were no significant effects of LED-supplements on sugar concentrations, while the reduced temperature on average did increase concentrations of d-fructose and d-glucose. Total glucosinolate concentrations were not different among treatments, although the most abundant glucosinolate, progoitrin, on average was present in highest concentration under LEDs containing far-red light, and in lower concentration at 9 °C compared to 15 °C. Conclusion The light quality of 24 h photoperiods in combination with temperature appears primarily important for growth and morphological traits in swede root bulbs. Influence of light quality and low temperature on appearance and sensory-related compounds may be utilized in marketing of root vegetables with special quality related to growth conditions of high latitude origin. © 2020 Society of Chemical Industry.

During 2012–2015, the seed vigour of 54 commercial sugar beet varieties was evaluated. In addition, correlations among different methods of determining seed vigour and the potential impact of low vigour on the quality traits of seeds and root yield were investigated. The chosen seed vigour indicators were field emergence (early and final count), emergence course in a phytotron under controlled conditions (early and final count, mean time of emergence, emergence uniformity) and germination ability under stress conditions regarding substrate moisture and air temperature. The most effective vigour indicators were field and phytotron emergence (early count), mean time of emergence and germination ability under stress conditions. Final field and phytotron emergence constituted weak indicators of seed vigour. Low seed vigour decreased root yield by 3.2 t/ha (4.8%) compared to high seed vigour. Lower yields were caused by slower and less uniform field emergence.

In the presented work attempts have been made to explore effectiveness of the sugar beet (Beta vulgaris L.) seeds priming process in relation to seed quality and environmental conditions. This study was conducted in three different field stations in the years 2013–2015 using two lots of sugar beet seeds of the variety Janosik that differed in their level of vigour. In the laboratory and phytotron experiments, pelleted and non-pelleted seeds were used while in the field experiments only pelleted seeds were used. Seed priming was carried out using two patented technologies based on the solid matrix priming method. The results of this study indicate that pelleting can reduce both seed viability and rate of germination, especially in the early stages. Both priming methods positively influenced seed germination ability and speed. The efficiency of priming was higher in seeds with lower vigour than those with higher vigour. It follows that priming seeds, especially those with lower vigour is particularly efficient. As a result, seed loss during treatment can be reduced. The obtained data indicate that priming reduces the differences in germination and the course of emergence caused by different levels of seed vigour and germination conditions. The higher vigour of seeds caused by priming was associated with the acceleration of leaf development and the increase in plant dry matter during the growing season. As a result, seed priming contributes to a significant increase in the technological yield of sugar. It should also be noted that the average weight of single root is less variable during harvesting.

Several studies have recommended the incorporation of environmental fluctuations in indoor experiments if closer-to-natural results in plant experiments are desired. Previous authors have suggested that if these fluctuations are not applied in synchrony, a stress effect could be present since plants have evolved to cope with synchronic environmental fluctuations. This study aimed to identify the effect of disparity in fluctuations of two important environmental variables, light quantity and temperature, on the growth of seven plant species from different functional plant types. A full-factorial combination of light and temperature under fixed or variable conditions was applied in phytotrons, and plant performance under these conditions was compared with a previous field trial. In all phytotron treatments, the average light and temperature conditions were the same as in the initial field trial. Productivity, leaf gas exchange, chlorophyll fluorescence, pigmentation, and other leaf traits were recorded in all species at the end of the experiments. Most plant trait responses were highly dependent on species and treatment, but some general trends were observed. Light fluctuations were mainly responsible for increases in specific leaf area (SLA) and chlorophyll a concentration, as well as for reductions in total dry weight and chlorophyll a/b ratio, independent if in combination with fluctuation or fixed temperatures. When fixed light conditions were combined with variable temperatures, the plants showed on average lower Fv/Fm values, Amax, and CO2 yield, while under variable light conditions and fixed temperatures, Fv/Fm increased compared with fully fixed or variable conditions. Although significant differences of plant traits between the field trial and all phytotron treatments were present (likely due to differences in other parameters that were not controlled in the phytotrons), our results still suggest that a synchronous variation of environmental factors lead to a more natural-like plant growth than if these factors are fixed or vary asynchronously.

Extreme heat-stress events have become more frequent due to climate change often with devastating effects on rice production. Accumulation and translocation of nitrogen (N) in rice organs is an important process that determines rice yield and quality. To assess the effects of short-term heat stress during booting stage on the accumulation and remobilization of N in rice plant organs, a pot-experiment in phytotron chambers was conducted using two cultivars (Nanjing 41 and Wuyunjing 24) at mean temperatures of 27 °C, 31 °C, 35 °C and 39 °C for 2, 4 and 6 days at booting stage. The results showed that high temperatures of 35 °C and 39 °C for 4 and 6 days significantly increased N concentration in leaves, stems, panicles and grains. Severe heat stress strongly reduced N translocation from leaves and stems into grains, resulting in an increased N distribution in stems and leaves. Moreover, N translocation efficiency of the vegetative parts decreased with increasing heat degree-days (HDD), and when HDD > 21.5 °C d, N translocation efficiency was negative, indicating re-accumulation of N in vegetative organs under severe heat stress. N concentration in leaves was positively associated with photosynthetic rate. Dry matter partitioning index of leaves and stems was positively correlated with their N concentration, whereas grain dry matter partitioning index was negatively correlated with grain N concentration. Heat stress reduced the ratio of grain number to leaf area, thereby reducing the proportion of sink to source. These results suggested that the low N translocation efficiency under heat stress could be due to a decrease in sink capacity. Our findings demonstrate that projected climate warming is likely to induce a significant reduction in N accumulation in rice grains by inhibiting the translocation of N from vegetative organs to grains.

Three main Ambrosia species (Ragweed)grow in Israel of which A. artemisiifolia and A. tenuifolia are of restricted distribution and the invasive A. confertiflora is the most abundant and widely distributed in roadsides, open land, waterways and cultivated fields and orchards. The present research was aimed to study the effect of temperatures regimes on the development and growth of the three main Ambrosia species in Israel, to elucidate the environmental conditions and plant traits that affect their development and infestation patterns. Seed germination studies were conducted in petri dish and pots. Ambrosia spp. plant emergence and development kinetics of different organs were conducted in pots and trays in a net house and at different temperature regimes in a phytotron. A. confertiflora, A. artemisiifolia and A. tenuifolia germinate best in light from the soil surface with no prerequisite of a stratification period. A. confertiflora seed emergence is inhibited at high temperature regimes (28-34oC), A. artemisiifolia at low temperature regimes (10-16oC) C, while A. tenuifolia is less affected by the temperature regimes. A. confertiflora plant height increased with increasing temperatures, and at lower temperatures develops a rosette. Root and rhizome biomass was less affected by the different temperatures regimes, A. artemisiifolia overground mass was not affected by temperature regimes while A. tenuifolia overground mass was reduced only at lower temperatures. The factors affecting A. confertiflora fast invasion and establishment are: easy long-distance seed dissemination, prolific seed germination and sprouting of rhizomes, rapid growth, massive viable seed fecundity, and adaptation to changing and adverse environmental conditions.

SUMMARY Rice is an important food crop in China, and the development of hybrid rice is a crucial way to increase grain yield. The creation of dual-purpose nuclear-sterile lines for two-line hybrid breeding has become vital for commercial rice breeding. We constructed the pC1300-2x35S::Cas9-sgRNAPTGMS2-1 expression vector for editing the male fertility gene PTGMS2-1 in two widely compatible rice varieties, 93-11 and Huazhan, by using the CRISPR/Cas9 system. We obtained the marker-free photoperiod-/thermo- sensitive genic male-sterile (P/TGMS) lines in T1 generation. According to the experiments in phytotron with four temperature and photoperiod treatments, we found the temperature is the main factor for restoring the pollen fertility of ptgms2-1 mutants in 93-11 and Huazhan, and the photoperiod also has some effects on pollen fertility in two different rice backgrounds. The application of cultivating new male-sterile lines by genome editing system will significantly accelerate the rice breeding process.

Withania coagulans is one of the most important medicinal species of the Solanaceae which has pharmacological properties for future research in drug development. Photosynthesis and morphological parameters in response to drought of this species have not been investigated as yet, though the issue is of interest. The factorial combination of four water deficit stress (20% (un-stressed control), 30%, 40% and 50% of FC depletion) and four landraces of W. coagulans (Fanuj, Khash, Saravan and Sarbaz) were laid out in a randomized complete design in a phytotron over the course of 180 days. The first, second, third and fourth samplings were performed every 45 day after imposing the treatments (DAT). The results demonstrated that increase in the water deficit stress levels, decreased minimal fluorescence (F0), leaf greenness, photosynthesis rate, plant height, leaf area, dry weight and quantum yield of PSII photochemistry )ФPSII(in all landraces and maximum photochemical efficiency of PSII (Fv/Fm) in Fanuj, but increased non-photochemical quenching)NPQ(and Fv/Fm in Saravan and Sarbaz landraces. The W. coagulans landraces such as Fanuj with the highest vector loadings of ФPSII at 135 and 180 DAT and Fv/Fm at 45 DAT and Sarbaz with the highest vector loading of F0 at 45 DAT were found suitable for unstressed and severe stress conditions, respectively. Among the chlorophyll fluorescence and morphological parameters, total dry weight had the significant positive correlations with plant height, leaf area and F0 at 45 DAT. Thus, this study indicated chlorophyll florescence should be measured at different phases and future studies should focus on the sensitivity of these parameters to detect potential times among subjects of different stresses. These parameters are easy, cheap, efficient and reliable physiological characteristics which can be used to guide the breeding of new resistant genotypes. According to results, W. coagulans can be called "Xerophytes Camel".

Seed-setting rate of rice (Oryza sativa L.) significantly decreases under high temperatures during the reproductive period largely due to heat-induced spikelet sterility. The effects depend largely on the timing and severity of heat stress, but the variation in the sensitivity of seed-setting rate in response to heat stress at different growth stages is not yet well simulated by most of the present crop models. To investigate the quantitative relationships between seed-setting rates of rice and various exposures of heat stress, we conducted four-year phytotron experiments with four different temperature regimes (the target maximum/minimum temperatures, 32 °C/22 °C, 35 °C/25 °C, 38 °C/28 °C and 41 °C/31 °C in 2011 and 2012; 32 °C/22 °C, 36 °C/26 °C, 40 °C/30 °C and 44 °C/34 °C in 2014 and 2015) with factorial combinations of durations (2, 4 and 6 days in 2014 and 2015; 3, 5 and 7 days in 2011; 3, 6 and 9 days in 2012) and the timings (0, 6 or 12 days after flowering), using three japonica cultivars. The duration and intensity of heat stress were quantified by the heat degree-days (HDD), defined as the temperature sum above a critical temperature value, which varied from 35 to 36 °C, depending on the cultivars. The observed seed-setting rates were well expressed as a logistic function of HDD, but the temperature sensitivity parameter varied with the timing of heat stress and the spikelet positions on the panicle. The variation in timing of flowering was apparent among upper, middle and lower parts of the panicles: 1 and 3-day delay of flowering for the spikelets on the middle and lower parts of the panicles, respectively, compared with upper ones. We therefore developed a simulation model that reflects the changes in the sensitivity of seed-setting rate to HDD to estimate the effects of heat stress with different intensities or durations at any time from flowering onward. The model with the stage-dependent parameters improved substantially the root mean square error (RMSE) and mean bias error (MBE) of seed-setting % from 20.1 and 6.0 to 7.6 and 0.2, respectively, compared to that with the stage-independent parameters. The proposed model needs to be tested under field conditions, but will be an important basis for accurate prediction of seed-setting rates in rice, which is critical for reliable estimates of crop production under climate change.

It is very significant to study the impact of deficit irrigation on crop growth and water use under the future scenarios with elevated CO2 concentrations and reduced water availability. This study investigated the growth and yield differences of maize grown in a phytotron in response to elevated CO2 concentrations under different irrigation treatments. Two irrigation treatments were carried out: regular irrigation (RI) and deficit irrigation (DI), in which the irrigation amounts were respectively 100 and 70% of evapotranspiration (ET), with four CO2 concentrations (400, 550, 700, and 900 μmol mol−1). Thus eight treatments, i.e. RI400, RI550, RI700, RI900, DI400, DI550, DI700, and DI900 were included in this study. Results show that, the relative reductions of stomatal conductance (gs) and transpiration rate (Tr) in response to elevated CO2 concentrations were higher under DI than RI, thus causing leaf temperature (Tleaf) rose higher under DI due to the transpiration cooling effect. As photosynthetic rate (Pn) and its physiological process were positively correlated with Tleaf, the relative increases of Pn and the resulting maximum leaf area index (LAImax), total dry matter weight (TDW), and grain yield (GY) react to elevated CO2 concentrations were higher under DI than RI, as well as the leaf water use efficiency (WUEL) and water productivity (WP). The DI900 treatment in which the irrigation amount was reduced by 30% only decreased the TDW and GY by 7 and 5% when compared with RI900. The variation of GY was consistent with the variation of kernels per ear (KPE), but was not directly related to hundred-grain weight (HGW). The above results show that when atmospheric CO2 concentrations rise in the future, deficit irrigation would be an effective way of saving water and would not only have a mitigating effect on water crises, but would also contribute to improving WP, which is more important in terms of actual production.

Climate change scenarios project an increase in the frequency of heat stress events, making it critical to quantify adverse heat stress effects on wheat production. Biomass growth determines much of grain yield in winter wheat, but it is substantially reduced under heat stress during the reproductive phase. In this study, leaf photosynthesis, biomass production, and leaf area index (LAI) dynamics were measured under various heat stress treatments in a 4-year phytotron experiment with two winter wheat cultivars. Heat stress at anthesis and during grain filling accelerated the measured degradation of leaf chlorophyll (SPAD) and resulted in a lower leaf photosynthesis rate with decreased final biomass growth. The observed relationships between leaf photosynthesis, LAI, and high temperatures were integrated into the WheatGrow model. In this study, we introduced a new cultivar parameter into the model to simulate cultivar difference in the sensitivity of biomass growth to heat stress. The new heat stress routines in the WheatGrow model significantly improved the simulated growth dynamics and the root mean square error (RMSE) with an independent validation data set for LAI and final aboveground biomass by 40% and 57% under heat stress treatments, respectively. This improvement in the crop model WheatGrow enables more reliable studies on climate change impacts and reduces uncertainties in simulations, particularly the impacts of extreme temperature events on crop growth and yields.

Climate change has brought more low temperature events and posed an increasing risk to the global wheat production. In order to evaluate the effects of low temperature at jointing and booting stages on wheat grain yield and its components, two years of environment-controlled phytotron experiments were carried out with two wheat cultivars under different low temperature levels and durations. Low temperature level and its interaction with low temperature duration had negative effects on the observed grain yield in two cultivars. Moreover, wheat yield was more sensitive to low temperature at booting than at jointing stages. Compared with the control treatment (T min /T max /T mean of 6 °C/16 °C/11 °C, T1), 4.6%–56.4% and 3.1%–44.6% decreases of grain yield per plant (YPP) were observed under low temperature at jointing in Yangmai16 (spring wheat) and Xumai30 (semi-winter wheat), and 13.9%–85.2% and 3.2%–85.9% decreases under low temperature at booting in Yangmai16 and Xumai30, respectively. The spike number per plant (SNPP) and grain number per spike (GNPS) were more sensitive to low temperature at jointing and booting stages than 1000-grain weight (TGW). Furthermore, significant negative linear relationships were observed between the accumulated cold degree days (ACDD) and YPP, SNPP, GNPS and TGW in both cultivars. The contribution of GNPS to the variation of YPP was greater than SNPP and TGW at the mild low temperature level (T min /T max /T mean of −2 °C/8 °C/3 °C, T3) in both cultivars. However, at the extreme low temperature level (T min /T max /T mean of −6 °C/4 °C/−1 °C, T5), the major variation of YPP was caused by SNPP of Yangmai16 and GNPS of Xumai30. In general, the decreased YPP under low temperature condition was mainly from the decreased grain number per plant (GNPP = SNPP × GNPS) in both cultivars and treatment stages, thus maintaining a high GNPP is very important for compensating the yield losses caused by low temperature at jointing and booting stages.

Background: Vegetable growers in Arctic areas must increasingly rely on market strategies based on regional origin and product quality. Swede roots (rutabaga) were grown in a phytotron to investigate the effect of high latitude light conditions on sensory quality and some health and sensory-related compounds. Experimental treatments included modifications of 24 h natural day length (69° 39' N) by moving plants at daily intervals to dark chambers with either no light, fluorescent growth light and/or low intensity photoperiod extension.; Results: Shortening the photosynthetic light period to 12 h produced smaller roots than 15.7 h and 18 h, with highest scores for bitter and sulfur taste, and lowest scores for sweetness, acidic taste and fibrousness. The photoperiod in combination with the photosynthetic light period also had an influence on glucosinolate (GLS) contents, with lowest concentrations in 24 h natural light and highest in 12 h natural light. Concentrations of vitamin C, glucose, fructose and sucrose were not significantly influenced by any of the treatments.; Conclusion: High latitude light conditions, with long photosynthetic light periods and 24 h photoperiod, can enhance sweet/less bitter taste and reduce GLS contents in swede roots, compared to growth under short day conditions. This influence of light conditions on eating quality may benefit marketing of regional products from high latitudes. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.

Fertility management techniques being promoted in sub-Saharan Africa (SSA) seek to grow indigenous vegetables economically and sustainably. This study was conducted in a phytotron chamber and compared yield, soil carbon (C) speciation and greenhouse gas (nitrous oxide (N2O) and carbon dioxide (CO2)) emissions from SSA soils of two ecoregions, the dry savanna (lna, Republic of Benin) and rainforest (Ife, Nigeria) cultivated with local amaranth (Amaranthus cruentus) under manure (5 t/ha) and/or urea (80 kg N/ha) fertilization. Vegetable yield ranged from 4331 kg/ha to 7900 kg/ha in the rainforest, RF, soils and 3165 kg/ha to 4821 kg/ha in the dry savanna, DS, soils. Yield in the urea treatment was slightly higher compared to the manure, and manure+urea treatment, but the difference was not statistically significant. Cumulative CO2 emissions over 21 days ranged from 497.06 to 579.47 g CO2-C/kg soil/day in the RF, and 322.96 to 624.97 g CO2-C/kg soil/day in the DS, while cumulative N2O emissions ranged from 60.53 to 220.86 mg N2O-N/kg soil/day in the RF, and 24.78 to 99.08 mg N2O-N/kg soil/day in the DS. In the RF samples, when compared to the use of urea alone, the combined use of manure and urea reduced N2O emissions but led to an increase in the DS samples. ATR-FTIR analysis showed that the combined use of manure and manure+urea increased the rate of microbial decomposition in the soils of the DS, but no such effect was observed in soils of the RF. We conclude that combining manure and urea fertilization has different effects on soils of the two ecoregions, and that RF farmers can reduce agricultural N2O emissions without compromising soil productivity and yield potential.

Background Salinity is one of the most widespread abiotic stresses affecting rice productivity worldwide. The purpose of this study was to establish the relative importance of different traits associated with salinity tolerance in rice and to identify new quantitative trait loci (QTL) conferring tolerance to salinity at seedling stage. A total of 231 F2:3 plants derived from a cross between a sensitive variety BRRI dhan29 (BR29 hereafter) and Capsule, a salt tolerant Bangladeshi indica landrace, were evaluated under salt stress in a phytotron. Results Out of the 231 F2 plants, 47 highly tolerant and 47 most sensitive lines were selected, representing the two extreme tails of the phenotypic distribution. These 94 plants were genotyped for 105 simple sequence repeat (SSR) and insertion/deletion (InDel) markers. A genetic linkage map spanning approximately 1442.9 cM of the 12 linkage groups with an average marker distance of 13.7 cM was constructed. QTL were identified on the long arm of chromosome 1 for Na+ concentration, K+ concentration, Na+-K+ ratio and survival; chromosome 3 for Na+ concentration, survival and overall phenotypic evaluation using the Standard Evaluation system (SES); and chromosome 5 for SES. A total of 6 pairwise epistatic interactions were also detected between QTL-linked and QTL-unlinked regions. Graphical genotyping indicated an association between the phenotypes of the extreme families and their QTL genotypes. Path coefficient analysis revealed that Na+ concentration, survival, Na+-K+ ratio and the overall phenotypic performance (SES score) are the major traits associated with salinity tolerance of Capsule. Conclusions Capsule provides an alternative source of salinity tolerance aside from Pokkali and Nona Bokra, the two Indian salt tolerant landraces traditionally used for breeding salt tolerant rice varieties. Pyramiding the new QTL identified in this study with previously discovered loci, such as Saltol, will facilitate breeding varieties that are highly tolerant of salt stress. Electronic supplementary material The online version of this article (10.1186/s12284-019-0319-5) contains supplementary material, which is available to authorized users.

Chilling stress has a strong negative impact on the growth and development of winter wheat (Triticum aestivum L.). To investigate the recovery of physiological function and yield formation by plant growth regulators following chilling stress, we performed low-temperature phytotron experiments at the booting stage, and sprayed 6-benzylamino adenine (6-BA), salicylic acid (SA), brassinolide (BR) and abscisic acid (ABA) after chilling stress. Plant growth regulators significantly enhanced SPAD value and net photosynthetic rate (Pn) in flag leaves following chilling stress (p

Accurately predicting crop development stage is key to simulating growth and yield formation in crop models. Low temperature stress is a major limitation to global wheat production and can significantly slow down wheat development rate. In a four-year environment-controlled phytotron experiments, detailed phenology datasets were obtained for low temperature stress treatments with different temperature levels and durations. Six widely-used temperature response functions (Linear, Bilinear Triangular, Trapezoidal, Bell-shaped, and Sin) for wheat phenology estimation were combined with WheatGrow model to simulate the low temperature stress effects on elongation-anthesis durations in order to test whether the effects of low temperature stress can be captured by current temperature response functions. In addition, a new algorithm for quantifying daily thermal sensitivity (DTS) was proposed and applied in the six temperature response functions to improve the prediction ability of phenology submodel under low temperature stress. The result indicates that anthesis stage was significantly delayed under low temperature stress at elongation and booting stages. All six original temperature response routines underestimated the delay of wheat development rate caused by low temperature stress, and the Linear and Triangular temperature response routines showed better performance than other four functions. A new improved DTS algorithm (DTSimproved) was proposed which can better quantify the delay of wheat development rate during low temperature stress and the recovery of development rate after low temperature stress. Model validation results show that compared with the DTSoriginal routine, all six improved phenology submodels (DTSimproved) significantly reduced the simulation error under low temperature stress, with the RMSE of elongation-anthesis duration under extreme low temperature stress (Tmin

BACKGROUND Marked effects of the climatic environment on fruit chemical composition have often been demonstrated in field experiments. However, complex covariations of several climatic factors in the natural environment complicate the interpretation of such experiments and the identification of the causal factors. This can be better achieved in a phytotron where the various climatic factors can be varied systematically. Therefore, we grew four black currant cultivars of contrasting origin in a phytotron under controlled post-flowering temperature and photoperiod conditions and analysed the berries for their ascorbic acid, sugar and organic acid contents. RESULTS The analyses revealed significant effects of genotype on all investigated compounds. Particularly large cultivar differences were observed in the concentrations of l-ascorbic acid (AA) and sucrose. The concentrations of both AA and dehydroascorbic acid (DHAA), as well as the concentrations of all major sugars, decreased consistently with an increasing temperature over the temperature range 12–24 °C. Fructose and glucose were the predominant sugars with concentrations several fold higher than that for sucrose. AA was the main contributor to the total ascorbate pool in black currant berries. The AA/DHAA ratio varied from 5.6 to 10.3 among the studied cultivars. The concentration of citric acid, which was the predominant organic acid in black currant berries, increased with an increasing temperature, whereas the opposite trend was observed for malic and shikimic acid. Quninic acid was always present at relatively low concentrations. By contrast, photoperiod had no significant effect on berry content of any of the investigated compounds. CONCLUSION It is concluded that the post-flowering temperature has marked effects on the concentration of important chemical compounds responsible for taste and nutritional value of black currant berries, whereas photoperiod has no such effect in the studied cultivars. © 2016 Society of Chemical Industry

Crop yield simulations are highly correlated to reproductive phase duration simulations, which are often affected by heat stress. In this study, we evaluated four widely used temperature response routines of wheat phenology (Bilinear, Sin, Beta, and Trapezoidal routines) to simulate heat stress effects on post-heading durations with datasets from four years of environment-controlled phytotron experiments and multi-year field experiments across the main wheat production region in China. Significant reductions in post-heading duration were observed with increasing heat stress in phytotron experiments. A comparison of these temperature routines imbedded in the WheatGrow model showed that three of the routines could not predict post-heading durations under heat stress, while the Trapezoidal routine tended to overestimate high temperature impacts. Therefore, the three routines that could not simulate heat stress effects were extended by a senescence acceleration function. This function significantly improved the post-heading duration simulations under heat stress, regardless of the original temperature routine. However, the temperature threshold of initiating the senescence acceleration function varied depending on the original temperature response routine, between 27.3 and 30.1 °C. A new genotypic coefficient representing a cultivar-specific sensitivity to heat stress was introduced and ranged from 1.4 to 5.7 times of none heat-affected senescence per day. When evaluating the three temperature response routines linked with the added senescence acceleration function with independent phenology data (130 measurements), resulted in an average RMSE of 2.2 days for post-heading duration. The improved post-heading duration simulation is important for simulating current year-to-year yield variability due to frequent heat events, and it is even more critical for climate change impact assessments.

Chloridea (Heliothis) virescens (F.) (Lepidoptera: Noctuidae) (tobacco budworm) management in pre-topped tobacco remains a concern for growers. Chlorantraniliprole, an anthranilic diamide insecticide, emerged as an option for C. virescens in early season tobacco because it selectively targets caterpillars, exhibits systemic action, and satisfies reduced risk classification. It is currently recommended for foliar application at threshold; however, because of its systemic action, many growers deploy soil applications at transplant. We conducted a series of experiments to determine the potential efficacy and longevity of soil applications of chlorantraniliprole for use against C. virescens in tobacco. First, tobacco plants were grown in the NCSU Phytotron, a controlled environment facility, and were treated with chlorantraniliprole soil applications either as a soil injection or soil drench at field equivalent rates at transplant. Plants were either watered daily or two times per week. A field experiment was established at two locations where at transplant in furrow and soil drench applications of chlorantraniliprole were compared to foliar applications. In both these experiments, one of the youngest leaves of adequate length on a subset of plants was sampled weeks three through nine after transplant in the phytotron and five through eight after transplant at the field stations. One-half of each leaf was exposed to second instar C. virescens to assess mortality and feeding, and the other half was analyzed for chlorantraniliprole concentration. Mortality differed between treatments in phytotron and field trials after 96 h exposure. Frass production and survivorship increased as plants grew. Phytotron trials demonstrated longer toxicity to C. virescens than field experiments, and chlorantraniliprole concentrations decreased at a slower rate in the Phytotron than in the field. Our field results suggest that soil applications of chlorantraniliprole are not likely to provide acceptable early season C. virescens control in the field.

Shifting temperature patterns on global and regional scales accredited to climate change will bring more low-temperature stress (LTS) and high-temperature stress (HTS) events to further deteriorate wheat yield and quality. Crop models can serve as a beneficial platform for quantifying the impact of both high and low-temperature events on grain yield (GY) and grain quality. Wheat grain protein concentration (GPC) and grain protein yield (GPY), as two important measurements of wheat quality for nutrition value, is often ignored in crop modeling efforts to improve grain yield under climate change. This study was undertaken for comprehensive comparison of four broadly used wheat simulation models (DSSAT-CERES-Wheat, DSSAT-Nwheat, WheatGrow, and APSIM-Wheat) in quantifying and simulating the responses of wheat grain quality (GPC and GPY) under LTS and HTS at critical growth stages, and to identify gaps in simulating wheat grain protein concentration and protein yield for crop model improvement. Four-year environment-controlled phytotron experiments were conducted with two wheat varieties under LTS (at joining and booting stages) and HTS (at anthesis, grain filling, and combined stress at anthesis and grain filling stages). For per unit increase in cold degree days (CDD, degree days below 2 °C) at jointing and booting stages and heat degree days (HDD, degree days over 30 °C) at anthesis, grain filling and combined stress at anthesis and grain filling stages, GPC was increased by 0.2% to 0.4% and 1.1% to 1.6%, while GPY was decreased by 2.1% to 4.5% and 0.3% to 1.7%, respectively. Most of the crop models tended to reproduce some HTS impacts better during grain filling than at anthesis, but all the tested models call for improvements in simulating LTS at different stages, especially for GPY. Our results indicated the need of incorporating response functions of extreme temperature stresses into grain quality models to adapt to future climate scenarios.

Gutierrez, W. A., and Shew, H. D. 2000. Factors that affect development of collar rot on tob acco seedlings grown in greenhouses. Plant Dis. 84:1076-1080. Collar rot, caused by Sclerotinia sclerotiorum, is an important disease of tobacco transplants produced under greenhouse conditions. Factors that affect the development of the disease were studied, including age of seedlings, presence of an external source of nutrients (leaf extract), clipping (leaf removal) practices, exposure to low temperature, and leaf injury caused by heat and a chemical. Flue-cured tobacco seedlings, cultivar K- 326, were grown in polystyrene cell trays floating on a nutrient solution. Trays were maintained in a phytotron growth chamber with a 28/18°C day/night temperature regime. Seedlings were inoculated with ascospores of S. sclerotiorum at the desired stage of growth by placing mature apothecia in the growth chamber and inducing ascospore release and deposition. Disease incidence was determined by examining seedlings for the presence of stem lesions over the next 15 to 21days. Seedlings between 35 and 53 days old were more susceptible to collar rot than younger or older seedlings. Inoculum efficiency was highest and disease was most severe when an external source of nutrients was present on leaf surfaces. Clipping of leaf tips did not increase disease, but if the leaf pieces created by clipping were left on seedlings, collar rot development was enhanced compared with treatments where debris was removed. Heat and chemical injuries that resulted in necrotic tissue provided highly susceptible infection courts for ascospores of S. sclerotiorum, but exposure to low temperature, which caused no visible injury, did not enhance infection. Adoption of cultural practices that minimize accumulation of leaf debris and eliminate factors that cause necrotic injury on leaves should greatly reduce the severity of collar rot of tob acco seedlings.

In Hokkaido, the northernmost region of Japan, soybean [Glycine max (L.) Merr.] crops are damaged by cold weather. Chilling temperatures negatively affect seed appearance by causing seed coat discoloration around the hilum region, which is called cold-induced discoloration (CD). An assay for CD tolerance using a phytotron was developed, and two quantitative trait loci (QTLs) associated with CD tolerance were identified. The major QTL was located in the proximal region of the I locus, and structural variation of this locus can serve as a useful DNA marker, called the Ic marker. To use this marker in breeding programs, the effects need to be assessed under field conditions because the Ic marker has been developed solely under phytotron conditions. The aim of this study was thus to assess the effect of the Ic marker under a cool field environment. We confirmed that the Ic allele was highly effective using 27 cultivars and breeding lines including a near-isogenic line grown in the field where severe cold-weather damage occurred. This allele had no negative influence on the agronomic traits in the near-isogenic line. Our results suggest that marker-assisted selection for the Ic allele is effective for improving CD tolerance in breeding programs.

High temperature stress influences pollen grains development in upland cotton (Gossypium hirsutum L.) anthers, resulting in anthers with an abnormal structure and pollen grains with a low germination rate. To examine the thermotolerance mechanisms of pollen grains in upland cotton, we observed pollen germination rates, pollen grain ultrastructure, anther structure, and the expression of heat shock protein (HSP) genes in pollen grains after the plants were continuously exposed to high temperatures (36/30°C) in a phytotron for 8 h every day over a period of 10 d. After the high-temperature treatment, the pollen germination percentage of the heat-sensitive cultivar was reduced compared with the heat-tolerant cultivar, and the structure of indehiscent anthers and the ultrastructure of pollen grains in the heat-sensitive cultivar were more abnormal than that in the heat-tolerant cultivar. There were more abnormal mitochondria, endoplasmic reticulum, and vacuoles as well as fewer starch granules in the pollen grains of the heat-sensitive cultivar compared with the heat-tolerant cultivar. The deformation of the pollen grain architecture may influence the pollen germination rate. The expression of the GhHSP90, GhHSP2, GhHSP7, and GhHSP8 genes was up-regulated to a greater extent in the heat-sensitive pollen grains compared with the heat-tolerant pollen during and after the high temperature period. The up-regulation of HSP gene expression may protect pollen grains from damage under high temperature stress (36/30°C). The structure of the anthers, ultrastructure of the pollen grains, and expression of HSP genes are related to the thermotolerance of pollen grains. These results provide a new approach for screening upland cotton cultivars for thermotolerance.

Heat stress significantly accelerates senescence process during reproductive phase in rice, but the effects of heat stress are not yet well simulated by most of the existing crop models. Three-year experiments under different temperature levels and temperature durations at anthesis and 12 days after anthesis were carried out in phytotron using two japonica cultivars. Significant positive correlations were observed between the shortened grain growing days from anthesis to maturity (GD AM ) and heat degree-days (HDD). The impact of post-anthesis heat stress on rice phenology was quantified by adding thermal effectiveness of heat stress to the original RiceGrow model. Performance of the improved model was tested with phenological data from different cultivars under post-anthesis heat stress of phytotron environments and field conditions. Validation results showed that root mean square error (RMSE), mean bias error (MBE) and variance of the distribution of differences ( S d 2 ) for the prediction of GD AM , decreased from 4.60 d, 2.65 d and 7.80 in the original model to 1.58 d, −0.16 d and 2.40 in the improved model, respectively, under post-anthesis heat stress conditions. The determination coefficient ( R 2 ) and index of agreement (IA) between simulated and observed GD AM , increased from 68.5% and 0.71 in the original model to 93.5% and 0.92 in the improved model under post-anthesis heat stress conditions, respectively. Overall, the improved model gave better predictions of GD AM in different rice cultivars under different post-anthesis heat stress environments. Our study highlights the necessity of accurately simulating the heat stress effects on phenological processes in rice to forecast crop production for ensuring food security under climate change reliably.

The influence of 3 temperatures: 4°, 13°, and 22°C and of 3 humidities 50% r.h., 77% r.h. and 95% r.h. on the effectiveness of two defolians KJ and Mg(ClO3)2•6H2O was investigated in a phytotron. By changing day and night temperature and humidity the weather conditions encountered in nurseries in autumn were simulated. The influence of environment on defoliation depended markedly on the species of plant and on the defoliant. In several cases defoliation started earliest at 13° but over a longer period of time the temperature 4° stimulated markedly leaf shedding.

Climate changes, particularly increases in temperature and CO2,are seriously challenging agriculture, and are one of the main factors that should be considered in the emergence of new diseases and their potential spread. Six trials were carried out to evaluate the effects of increased temperature and CO2 on the severity of leaf spot of lettuce, caused by Allophoma tropica (syn. Phoma tropica), a pathogen that was first observed on lettuce in northern Italy in 2011. Temperature, CO2 and their interactions were significant factors (P

The functional relationship between binucleate Rhizoctonia sp. (BnRhizoctonia) and apple was investigated. Apple rootstock plantlets (Malling 9) were grown in BnRhizoctonia inoculated and non-inoculated soil after preliminary treatment with gamma-rays. A growth assay was performed in phytotron under two soil-water content regimes: an optimal one for plant growth and another inducing periodic plant water stress. At the end of the growth test, plant growth as fresh and dry weight of biomass produced over the trial period and fungal root colonization with culture-based methodology were estimated. Relative quantification of Rhizoctonia and soil fungi DNA using specific primers was performed. Overall, BnRhizoctonia inoculation gave a mean plant growth increase which accounted for 50% as compared to non-inoculated treatments. Although root colonization frequency did not differ between inoculated and uninoculated plants, the inoculated were highly colonised by BnRhizoctonia, whilst the others were colonized by a series of ascomycetes such as Fusarium spp., Alternaria sp. which quickly recolonized soil after preliminary soil treatment with gamma-rays acting soil microbial restoration. Water stress overall reduced plant growth; however, inoculation with BnRhizoctonia reduced this negative effect by about 30%. Findings of this study indicate that BnRhizoctonia acts as growth promoter; but this beneficial effect depends on its degree of root colonization and is affected by environmental interaction.

Low temperature greatly affects wheat production, while low-temperature pretreatments may enhance plant tolerance to subsequent low-temperature stress. However, the knowledge on grain yield formation responses to multiple low-temperature stresses under natural conditions is still limited. Here, two years of environment-controlled phytotron experiments were carried out with two wheat cultivars under different low-temperature levels, periods and frequencies, and the temperature regimes in this study were designed to be similar to the daily variation in natural temperature. Spring frost (canopy temperature fall below 0 °C or Stevenson screen air temperatures below 2 °C) had negative effects on grain yield and yield components for both cultivars. Moreover, wheat yield was more sensitive to low temperatures at booting than at jointing. The reduction in grain yield under low-temperature conditions was mainly attributed to the decreased spike number per plant (SNPP) and grain number per spike (GNPS). Furthermore, grains in the apical spikelets were the most sensitive to spring frost, followed by those in the basal and central spikelets. Compared to the non-low-temperature-pretreated plants, the low-temperature-pretreated plants did not have an increased grain yield, except at T4 (Tmin/Tmax/Tmean, −6 °C/4 °C/−1 °C). Grain yield under T4 probably increased because severe low temperatures killed parts of the tillers, which resulted in carbon and nitrogen relocation to the roots, young tillers and axillary buds. As a result, the young and new tillers in the axillary buds grew rapidly and eventually formed spikes.

O objetivo deste trabalho foi avaliar a biologia e a tabela de vida de fertilidade do pulgão-preto da videira [Aphis illinoisensis (Hemiptera: Aphididae)], em mudas das cultivares de Vitis labrusca Bordô, e de V. vinifera Cabernet Franc, Itália e Moscato Bianco. O experimento foi conduzido em 50 minigaiolas de confinamento, com um inseto em cada gaiola por tratamento, fixadas em mudas de videira mantidas em câmara de crescimento do tipo fitotron (a 25±1°C, umidade relativa de 75±10% e fotófase de 14 horas). Avaliaram-se diariamente a duração e a viabilidade ninfal, a fecundidade e a longevidade do período reprodutivo da espécie. O pulgão-preto da videira completou o ciclo biológico nas mudas das mencionadas cultivares, com duração da fase de ninfa de 7,9±0,3, 6,8±0,2, 6,2±0,2 e 6,7±0,2 dias, e viabilidade de 58, 82, 98 e 80% para 'Bordô', 'Cabernet Franc', 'Itália' e 'Moscato Bianco', respectivamente. 'Cabernet Franc' e 'Moscato Bianco' foram mais favoráveis ao desenvolvimento do pulgão-preto, com base na tabela de vida de fertilidade, com 51,3 e 55,6 descendentes por fêmea, por geração, respectivamente. 'Bordô' foi a menos adequada ao desenvolvimento do afídeo, com 12,55 descendentes por fêmea, por geração, o que indica resistência do tipo antibiose ou não preferência do inseto pela cultivar.

In the present study, heat treatment was carried out in five different phenological phases, from the first node detectable (DEV31) growth stage to 20 days after flowering, on four wheat genotypes with very different adaptation strategies. They were grown in a controlled environment in a phytotron chamber and exposed to a night temperature of 20°C and a day temperature of either 30°C, at DEV31, or 35°C at all the later developmental phases, for an interval of 14 days. Plant height, leaf number, number of tillers, grain number and grain weight per main and side spikes, TKW per main and side spikes, length of the main and side spikes, and spikelet number per main and side spikes were recorded. High temperature enhanced the stem growth intensity, plant height and tiller number. In contrast, the length of side spikes, spikelet no./side spike, grain no./main and side spike, grain weight/main and side spike and TKW/main and side spike were significantly decreased. The stress response depended strongly on the developmental phase in which the heat stress was applied. Fleischmann 481 and Soissons showed definitely contrasting tendencies both in grain number and grain weight. In the case of the Plainsman V and Mv Magma pair, the higher heat stress tolerance of Magma compared to Plainsman V was evident also from the grain number and weight of the main spike at each developmental phase.

Neither methodology nor guidelines are available for defining quality characteristics and storage conditions of seed material harvested from semi-natural grassland. Seeds from an Arrhenatherion meadow were harvested via on-site threshing and seed stripping. After determination of purity, thousand seed weight and pre-tests in a phytotron, germination-capacity trials were carried out in a greenhouse. The harvested seed material was stored for up to 3 years under different conditions: (i) room temperature 18–23°C, (ii) cooling chamber (2–5°C with 40–50% humidity) and (iii) freezer (−18°C). There was a significant impact of the tested harvesting methods on seed separation, thousand seed weight and purity, but not on the germination capacity. Different storage conditions and storage length significantly influenced the germination capacity. There were also generally higher germination values for the seed-stripping material than the on-site threshing material (ca. 70 and 60%, respectively, in the first year). Germination capacity decreased significantly with time and was

In Hokkaido, northern Japan, soybean [Glycine max (L.) Merr.] crops are damaged by cold weather. Chilling temperatures result in the appearance of cracking seeds (CS) in soybean crops, especially those grown in eastern and northern Hokkaido. Seed coats of CS are severely split on the dorsal side, and the cotyledons are exposed and frequently separated. CS occurrence causes unstable production because these seeds have no commodity value. However, little is known about the CS phenomenon. The aims of this study were to identify the cold-sensitive stage associated with CS occurrence and to develop a method to select CS-tolerant lines. First, we examined the relationship between chilling temperatures after flowering and CS occurrence in field tests. The average temperature 14 to 21 days after flowering was negatively correlated with the rate of CS. Second, we evaluated differences in CS tolerance among soybean cultivars and breeding lines in field tests. ‘Toyohomare’ and ‘Toiku-238’ were more CS-tolerant than ‘Yukihomare’ and ‘Toyomusume’. Third, we developed a selection method in which plants were subjected to 21-day chilling-temperature treatment from 10 days after flowering in a phytotron. This enabled comparisons of CS tolerance among cultivars. This selection method will be useful for breeding CS-tolerant soybeans.

An investigation was carried out to understand the physiological mechanisms of male sterility in rice. The critical sterility temperature and critical stage of thermosensitivity of the selected TGMS (Thermosensitive Genie Male Sterile) line, TS 29 was studied using a Phytotron. Variations in the physiological traits were analyzed at Stage VII of panicle development (Filling phase of pollen, floret and panicle reach full length and colour turns to green). High significant reductions in photosynthetic rate, transpiration rate, hill reaction, sugars and carbohydrate contents were recorded. The high temperature induced male sterility in TGMS line was associated with accumulation of starch and higher diffusive resistance. However a reverse of all the above responses was found in the TS 29 grown under fertility inducing low temperature and in the variety CO 46. The results revealed that some physiological traits play an important role by acting as signals or messengers in response to temperature leading to pollen abortion.

An increase in mean and extreme summer temperatures is expected as a consequence of climate changes and this might have an impact on plant development in numerous species. Root chicory (Cichorium intybus L.) is a major crop in northern Europe, and it is cultivated as a source of inulin. This polysaccharide is stored in the tap root during the first growing season when the plant grows as a leafy rosette, whereas bolting and flowering occur in the second year after winter vernalisation. The impact of heat stress on plant phenology, water status, photosynthesis-related parameters, and inulin content was studied in the field and under controlled phytotron conditions. In the field, plants of the Crescendo cultivar were cultivated under a closed plastic-panelled greenhouse to investigate heat-stress conditions, while the control plants were shielded with a similar, but open, structure. In the phytotrons, the Crescendo and Fredonia cultivars were exposed to high temperatures (35°C day/28°C night) and compared to control conditions (17°C) over 10 weeks. In the field, heat reduced the root weight, the inulin content of the root and its degree of polymerisation in non-bolting plants. Flowering was observed in 12% of the heat stressed plants during the first growing season in the field. In the phytotron, the heat stress increased the total number of leaves per plant, but reduced the mean leaf area. Photosynthesis efficiency was increased in these plants, whereas osmotic potential was decreased. High temperature was also found to induced flowering of up to 50% of these plants, especially for the Fredonia cultivar. In conclusion, high temperatures induced a reduction in the growth of root chicory, although photosynthesis is not affected. Flowering was also induced, which indicates that high temperatures can partly substitute for the vernalisation requirement for the flowering of root chicory.

In the last decades, several studies have reported the increase of land degradation and desertification in the Mediterranean Basin. Depending on degradation severity, ecological restoration might be needed in order to promote ecosystem recovery. The ecology of the selected species and intra specific variability should be considered in order to improve restoration options, especially facing climate change. The present study tested the hypothesis that seedlings from drier provenances would be better adapted to low water content conditions. Seeds were germinated under controlled temperature after which seedlings were grown in a phytotron under two contrasting watering regimes. Seedling performance was analysed using morphological and physiological parameters. Low water content had a clear negative effect on the seedlings’ aboveground biomass (total dry weight, root collar diameter, leaf dry weight and leaf weight ratio) and a positive effect on belowground biomass (root weight and root:shoot ratio). This response was not unequivocal, since provenances differed in morphological adaptations to low water content. Seedlings from the wettest provenance revealed a higher relative growth rate under high water content but a poor adaptation to limited water availability when compared to the other two provenances. This was observed by the absence of a significant belowground investment in this provenance. Seedlings from the wettest provenance also presented a significant reduction of total leaf area that was not observed in the other two provenances. This can however be hardly considered as a successful adaptation to cope with drought since this provenance produced less sclerophyllous leaves, less belowground biomass and also lower sapwood to leaf area ratio independently from the water content conditions. By contrast, seedlings from the dry provenance with the hottest summer had similar root collar diameter, leaf dry weight and physiological performance under both watering regimes. The observed adaptations to water regimes seem to be related with the climate of the seed source and highlighted the importance of seed provenance in ecological restoration actions using Mediterranean species. This knowledge could improve early establishment success predictions for different plant populations, allowing more reliable and cost-effective management decisions under climate change scenarios.

Investigations on the influence of the photoperiod on the utilization of mineral nutrients by tomatoes, 'Karzełek Chodowski' cv. and spinach 'Matador' cv. were performed in a phytotron. The biomass of experimental plants increased with the length of the photoperiod, for tomatoes and spinach from 9 to 16 and from 9 to 14 hours depending on the concentration of nutrient solution. The percentage of macronutrients in the biomass of both plants increased, the higher the salt concentration of the solution, only during the appropriate lenght of the day. The utilization of mineral nutrients regardless of their concentration reached a maximum for tomatoes and spinach in the conditions of 16 and 11 hour day respectively.

Bacterial wilt, caused by Ralstonia solanacearum , is responsible for severe losses in tomato crops in the world. In the present study, the effect of temperature, cultivars of tomato, injury of root system and inoculums load of R. solanacearum to cause bacterial wilt disease under control conditions was undertaken. Three strains UTT-25, HPT-3 and JHT-5 of R. solanacearum were grown at 5–40 °C in vitro to study, the effect of temperature on the growth of bacteria and maximum growth was found at 30 °C after 72 h in all the strains. Twenty-one days old seedlings of two cultivars of tomato i.e. N-5 (moderately resistant) and Pusa Ruby (highly susceptible) were transplanted into the pots and inoculated with R. solanacearum strain UTT-25 (5 × 108 cfu/ml), mechanically injured and uninjured roots of the plant. The plants were allowed to grow at 20, 25, 30 and 35 °C at National Phytotron Facility, IARI, New Delhi to study the effect of temperature on intensity of bacterial wilt disease. Maximum wilt disease inten...

Nocturnal warming has various effects on plant biomass production. To understand how biomass production of the dominant grassland species Leymus chinensis responds to summer nocturnal warming in the eastern temperate Eurasian steppes, we simulated summer nocturnal warming (+4 °C) using a phytotron system for 100 days operated based on the variation of diurnal temperatures over the past 12 years in the Songnen Grasslands. Our results show summer nocturnal warming significantly increased above-ground biomass production of parent and daughter shoots as well as increased below-ground root and rhizome biomass production; rhizome biomass increased faster than root biomass leading to an increase in the rhizome biomass to root biomass ratio. Nocturnal warming slightly increased the number of daughter shoots per plant, and significantly increased the number of buds in the below-ground bud bank and the number and length of rhizomes per plant. Also, the dark respiratory and net photosynthetic rates, Jmax, the rate of triosephosphate utilization and chlorophyll fluorescence parameters (ΦPSII and qP) were significantly higher under nocturnal warming conditions. These findings show that nocturnal warming in this ecosystem improves individual biomass accumulation due to photosynthetic compensation, and may enhance the population density and productivity of L. chinensis by increasing bud number in the below-ground bud bank during the early stage of ecological succession for grasslands dominated by L. chinensis.

The impacts of climate modification were examined in terms of changes in the stress tolerance of winter wheat varieties. The enzyme reactions of two winter wheat varieties to drought stress, simulated by water withholding in three different phenophases, were analysed in a phytotron experiment in the Centre for Agricultural Research, Hungarian Academy of Sciences. Plants were raised either at ambient CO2 level or at twice this concentration. The quantities of glutathione reductase (GR), glutathione-S-transferase (GST), catalase (CAT), guaiacol peroxidase (POD) and ascorbate peroxidase (APX) were determined from leaf samples collected at the end of the drought treatment.The results showed that antioxidant enzymes may help to counterbalance the reactive oxygen species induced by stress during various stages of the vegetation period. Although there were substantial differences in the changes induced in the activity of individual enzymes by modifications in environmental factors, this activity and its response to stress depended not only on these factors, but also on the developmental stage of the plant. Modifications in enzyme activity could indicate that enhanced CO2 concentration delayed the development of drought stress up to first node appearance, and stimulated antioxidant enzyme activity when drought occurred during ripening.

Infection with fungal pathogens on wheat varieties with different levels of resistance was tested at ambient (NC, 390 ppm) and elevated (EC, 750 ppm) atmospheric CO2 levels in the phytotron. EC was found to affect many aspects of the plant-pathogen interaction. Infection with most fungal diseases was usually found to be promoted by elevated CO2 level in susceptible varieties. Powdery mildew, leaf rust and stem rust produced more severe symptoms on plants of susceptible varieties, while resistant varieties were not infected even at EC. The penetration of Fusarium head blight (FHB) into the spike was delayed by EC in Mv Mambo, while it was unaffected in Mv Regiment and stimulated in Mv Emma. EC increased the propagation of FHB in Mv Mambo and Mv Emma. Enhanced resistance to the spread of Fusarium within the plant was only found in Mv Regiment, which has good resistance to penetration but poor resistance to the spread of FHB at NC. FHB infection was more severe at EC in two varieties, while the plants of Mv ...

Cold water irrigation and growth in low temperature phytotron are two commonly used methods to evaluate cold tolerance of rice at the seedling stage and the cold sensitive seedlings exhibit different injury symptoms, respectively. However, so far no one has systematically dissected the differences of cold tolerance at seedling stage in rice under the two cold environments. We used a recombinant inbred line (RIL) population derived from a cross of a cold-tolerant japonica cultivar, Lijiangxintuanheigu and a cold sensitive indica cultivar, Sanhuangzhan-2 for this study. The cold sensitive seedlings exhibited leaf yellowing after cold water irrigation and leaf rolling during growth in the low temperature phytotron. Leaf yellowing and leaf rolling in RILs was significantly correlated, but the correlation coefficient was low. A total of four quantitative trait locus (QTLs) on chromosomes 1, 6, 9 and 12 were detected using leaf yellowing and percent seedling survival as indicators of cold tolerance after cold water irrigation, while five QTLs on chromosomes 7, 8, 9, 11 and 12 were detected using leaf rolling and percent seedling survival as indicators of cold tolerance during growth in the low temperature phytotron. The two QTLs, qCTS-9 and qCTS-12 were detected using different evaluation indicators under the two cold environments. Our results suggest that rice cold tolerance mechanisms at the seedling stage differ between the two environments, but the detection of common QTL implies the existence of overlap in the metabolic pathways for cold tolerance. The two common QTLs have potential value in rice breeding.

The heading characters and morphological traits of two partial sets of wheat–barley disomic addition lines, namely Mv9kr1/Igri and Asakaze/Manas, were evaluated under controlled environmental conditions in a phytotron under long-day, short-day and non-vernalised conditions and in field-sown experiments. The winter barley chromosome additions significantly influenced the flowering time of wheat both in the controlled environment test and under field-sown conditions. Of all the barley addition lines, the effect of the 4H and 7H additions was the most characteristic. The 7H addition lines were the earliest in both cultivar combinations in each treatment. In the Mv9kr1/Igri combination the 4H addition was the latest under all the environmental conditions. In the Asakaze/Manas combination 4H addition was the latest under short-day and long-day illumination in the phytotron but the 6H addition was the latest without vernalisation and in the field in 2012. There was 12 and 11 days difference between the flowering times of the 7H and 4H Mv9kr1/Igri and Asakaze/Manas addition lines in the field in 2012, which increased to 52 and 44 days under short-day illumination in the phytotron. In the winter wheat background, the addition of 2H carrying the photoperiod sensitivity gene Ppd-H1 decreased the flowering time under the short photoperiod regime, but had a very strong delaying effect under field-grown conditions. Considering the yield components under field conditions, 4H was the most fertile of the addition lines, while 7H showed the highest tillering capacity, and Igri 3H had good tillering capacity and the highest number of seeds per plant.

Phytotron experiments were conducted to examine the impact of elevated atmospheric CO2 level (750 μmol mol−1) on the drought tolerance of winter barley (Petra), durum wheat (Mv Makaroni) and spring oat (Mv Pehely) varieties. Under drought stress conditions, the durum wheat variety was found to be unaffected by CO2 enrichment, as neither the biomass or grain yield nor the antioxidant enzyme activities changed compared to those at ambient CO2. Despite the fact that the spring oat variety had similar grain yield loss due to drought at both CO2 levels, it exhibited reduced antioxidant enzyme activities under less severe drought, indicating a slightly increased tolerance to drought. Winter barley, which exhibited an extremely positive reaction to CO2 enrichment at the control water supply level, also showed increased drought tolerance in response to high CO2. It had low glutathione reductase, glutathione-S-transferase and ascorbate peroxidase activities even at the most severe drought stress levels, while it could also fully compensate for the negative effects of drought on biomass and grain yield parameters when grown at elevated CO2.

Drought stress frequently occurs in the reproductive stage of wheat, causing significant yield loss. To study the developmental stage dependency of the effect of drought stress on photosynthesis, plants of the drought-tolerant Plainsman V and sensitive Cappelle Desprez winter wheat varieties were grown in phytotron chambers and subjected to water withholding during three phenophases of reproductive development: meiosis, anthesis and early seed development (ESD).Stomatal conductance (gs) and net photosynthesis (Anet) showed similar characteristics. Meiotic-stage drought only decreased the values of Cappelle Desprez significantly. Stressed Plainsman V showed a significantly smaller reduction and better regeneration for these parameters at anthesis. The decreases in gs and Anet were similar in both varieties when drought was applied during ESD. Studies on the intercellular CO2 concentration (Ci) inflexion point implied that metabolic impairment was less typical of stressed Plainsman V than of Cappelle Desprez at meiosis and anthesis. The quantum efficiency of PSII (ΦPSII) did not decline in either genotype during meiotic-stage drought. Stressed Plainsman V showed significantly higher ΦPSII values compared to Cappelle Desprez at anthesis. During ESD, the values for stressed plants of both genotypes decreased to a similar extent.The results indicate that the effect of drought stress on photosynthesis shows developmental stage dependency during the reproductive life cycle of wheat.

Effect of different growth temperature regimes was studied on morphological and flowering characters of two gladiolus cultivars viz. Snow Princess and American Beauty. Both the cultivars were raised in Phytotron using corm size of 3.5–4.0 cm in diameter. Temperatures treatments were maintained 20/18, 26/22 or 30/26 °C (Day/Night) with 14 h light and 60–65 % relative humidity in the growth chambers. Days required for corm sprouting decreased as the temperature levels increased. 30/26 °C temperature was found with lowest days for corm sprouting. Sprouting percentage of corms was 100 % under all the treatments in both the cultivars. There was non-significant difference in leaf number and number of florets per spike under all the temperature. Number of florets was maximum at 20/18 and 26/22 °C temperatures and was nil at 30/26 °C. The taller spike and rachis length was found under treatment T2 (26/22 °C) in cultivar American Beauty. The duration of flowering reduced with the temperature increase. Maximum duration of flowering on spike (5.67 day) was found in control treatment (20/18 °C). With few exceptions, adverse effect of increase in temperature was substantial. However, the effect of highest temperature of 30/26 °C was more adverse and significant for various vegetative and reproductive growth parameters in both the cultivars. Increase in temperature concomitantly decreased flower initiation, hastened sprouting of corms and increased plant height.