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Knowing the morphogenesis of forage species is an essential condition for the correct management of grazing in arid environments. Our aim was to define cardinal temperatures and morphogenetic characters for Poa ligularis and Bromus pictus, the most preferred and endangered Patagonian grass species. We grew plants in growth chambers at different temperatures under adequate water and nutrient supply. Our results were similar to those reported for other temperate species: base temperatures: 0°C, optimal temperatures: ≈22°C and maximum temperatures: ≈27.5°C for both species, and phyllochrons: 212.8 and 222.2 GDD (growing degree days), leaf appearance rates (LAR): 0.0047 and 0.0045 leaves.GDD−1, number of living leaves (NLL): 2.7 and 2.9 per tiller and leaf lifespan (LLS): 582 and 662 GDD, for P. ligularis and B. pictus, respectively. Cardinal temperatures, LAR and phyllochron did not differ between these species but NLL and LLS were lower for P. ligularis than for B. pictus. Results shown these species are similar to other temperate grasses under non-limiting water and nutrient conditions. These findings are the first step to propose field experiments that allow the accurate estimation of grazing and resting times in order to avoid consumption of unexpanded leaves and allow tillers to attain their maximum NLL. [ABSTRACT FROM AUTHOR]

Breeding for high nitrogen-use efficient crops can contribute to maintaining or even increasing yield with less nitrogen. Nitrogen use is co-determined by N uptake and physiological use efficiency (PE, biomass per unit of N taken up), to which soil processes as well as plant architectural, physiological and developmental traits contribute. The relative contribution of these crop traits to N use is not well known but relevant to identify breeding targets in important crop species like maize. To quantify the contribution of component plant traits to maize N uptake and use, we used a functional-structural plant model. We evaluated the effect of varying both shoot and root traits on crop N uptake across a range of nitrogen levels. Root architectural traits were found to play a more important role in root N uptake than physiological traits. Phyllochron determined the structure of the shoot through changes in source: sink ratio over time which, in interaction with light and temperature, resulted in a significant effect on PE and N uptake. Photosynthesis traits were more relevant to biomass accumulation rather than yield, especially under high nitrogen conditions. The traits identified in this study are potential targets in maize breeding for improved crop N uptake and use. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the impact of two harvest frequencies (60 and 90 days) on the morphogenic and structural characteristics of four Elephantgrass genotypes (two tall and two dwarf) in both rainy and dry seasons. The research was conducted in Garanhuns, Brazil from September 2019 to December 2021. The morphogenic characteristics evaluated included leaf appearance rate, stem and leaf elongation rate, phyllochron, plant height, stem diameter, leaf and stem length, basal tiller population density, and number of leaves per tiller. The results showed that Elephant B had the highest leaf elongation rate among all genotypes, both in the rainy and dry seasons. During the rainy season, the tall genotypes showed higher stem elongation rates compared to the dwarf genotypes. The tall genotypes also had lower phyllochron values. Taiwan A‐146 2.37 had a higher population density of basal tillers by 30%–37% compared to other genotypes. During the dry season, the stem elongation rate of Taiwan A‐146 2.37 was slower compared to the rainy season. The study showed that the harvest frequency had an effect on the morphogenic characteristics of Elephantgrass genotypes, with 60 days harvest resulting in higher leaf elongation rates. Elephant B was superior in terms of leaf elongation at both harvest frequencies. The results indicate that the season also plays a role in the morphogenic characteristics of the genotypes. This study provides insights into the optimal cutting strategies for Elephantgrass based on the size of the plant and season. [ABSTRACT FROM AUTHOR]

This study assessed the nitrogen nutrition index, morphogenic characteristics and tiller structure of Alexandergrass (Urochloa plantaginea (LINK) Hitch) pasture submitted to different nitrogen (N) levels (zero, 150 or 300 kg ha-1 of N). The experimental design was entirely randomized with repeated measures arrangement. The experimental animals were Angus heifers under rotational stocking grazing method. The number of animals was variable to keep 30±5 cm post-grazing sward height. Nitrogen nutrition index increased linearly according N levels (Ŷ = 59.8 + 0.1216N; P < 0.0001; r²=0.53). The leaf appearance rate adjusted to a positive linear regression model according the thermal sum (TS) with zero of N (Ŷ0N = 0.0077 + 0.0000087TS; P = 0.0308; r² = 0.72) and 150 kg ha-1 of N (Ŷ150N = 0.0020 + 0.000021 TS; P = 0.0022; r² = 0.92). The use of 300 kg ha-1 of N did not alter the leaf appearance rate (0.0124 leaf degree-days-1). The use of up to 300 kg ha-1 of N increases the Alexandergrass nitrogen content. The leaf appearance rate in Alexandergrass is modified using N while the morphogenic characteristics leaf expansion, stem expansion, phyllochron, leaf lifespan, leaf elongation duration and tiller structure are not altered by N utilization. [ABSTRACT FROM AUTHOR]

Barley is a long-day plant with a major gene (PPD-H1) that determines its photoperiod sensitivity. Under long days (i.e. 16 h), flowering occurs earlier in sensitive (Ppd-H1) than in insensitive (ppd-H1) genotypes, while under short days (i.e. 12 h) both flower late and more or less simultaneously. We hypothesized that (i) the sensitive line should flower later than the insensitive line under very short days (<12 h), and (ii) both the sensitive and insensitive lines should have similar phenology under very long days (>18 h). When comparing a pair of spring isogenic lines for sensitive and insensitive PPD-H1 alleles (introgressing the PPD-H1 allele into the barley cultivar 'WI4441'), we found responses fully in line with expectations for the commonly explored range from 12 to 16–18 h. When the responses were extended to very short days, sensitivity increased noticeably, and time to flowering of the sensitive line was longer than that of the insensitive one. Under very long days, the sensitive line did not respond further (it seemed to have reached its minimum time to flowering under a 16 h period), while the insensitive line continued shortening its time to flowering until c. 21 h. Consequently, both lines flowered similarly under very long days, which opens opportunities to easily test for differences in earliness per se , as in wheat. [ABSTRACT FROM AUTHOR]

Background: The time between the appearance of successive leaves, or phyllochron, characterizes the vegetative development of annual plants. Hypothesis testing models, which allow the comparison of phyllochrons between genetic groups and/or environmental conditions, are usually based on regression of thermal time on the number of leaves; most of the time a constant leaf appearance rate is assumed. However regression models ignore auto-correlation of the leaf number process and may lead to biased testing procedures. Moreover, the hypothesis of constant leaf appearance rate may be too restrictive. Methods: We propose a stochastic process model in which emergence of new leaves is considered to result from successive time-to-events. This model provides a flexible and more accurate modeling as well as unbiased testing procedures. It was applied to an original maize dataset collected in the field over three years on plants originating from two divergent selection experiments for flowering time in two maize inbred lines. Results and conclusion: We showed that the main differences in phyllochron were not observed between selection populations but rather between ancestral lines, years of experimentation and leaf ranks. Our results highlight a strong departure from the assumption of a constant leaf appearance rate over a season which could be related to climate variations, even if the impact of individual climate variables could not be clearly determined. [ABSTRACT FROM AUTHOR]

Phyllochron, the reciprocal of the leaf appearance rate, is a critical genetic parameter in crop models for predicting growth characteristics and yield. Previous studies have shown that existing observations and predictive algorithms do not adequately represent a broad range of cultivars and environments. Here, we conducted a series of experiments in the field to quantify and disentangle the effects of sowing date and cultivar on maize leaf collar appearance (LCA). A bilinear model was found to accurately fit maize LCA (R2 adj > 0.99); this model revealed a slower rate of LCA for the first leaves compared to the last leaves. Turning points in the model occurred between the 9.2th and the 13.1th leaf, nearly always below the ear leaf and around a leaf age index (LAI) of 60.0%. The phyllochron before the turning point (PHYLL Ⅰ) was significantly higher than the phyllochron after the turning point (PHYLL Ⅱ) for all three maize cultivars, and PHYLL Ⅰ was approximately two times higher than PHYLL Ⅱ on average. Both PHYLL Ⅰ and PHYLL Ⅱ were significantly affected by sowing date and cultivar. Variations in PHYLL Ⅰ and PHYLL Ⅱ indicated strong plasticity in maize phyllochron at different leaf ranks. The results of this study are critical for improvement of maize management practices and extend the applicability of phyllochron-collar measurements in crop models. • Bilinear models could accurately predict maize leaf appearance time. • Turning points consistently occurred when the leaf age index was 60.0%. • Phyllochron was greater in earlier leaves than in later leaves. [ABSTRACT FROM AUTHOR]

Air temperature and photoperiod play an important role in the seedling development for tropical forest species. Both variables are sensitive to climate, and so evaluating thermal and photoperiodic effects on seedling development is fundamental, especially for climate change studies. Methods to quantify thermal time and the energy required for plants to reach a development stage include air temperature and cardinal temperatures. The photoperiod will also affect physiological reactions of a plant and thus its development. Here we evaluated the six thermal time methods widely used to compute thermal requirement, and identified the influence of the photoperiod from the 2015 and 2016 growing seasons and 12 sowing dates in Itajubá, Minas Gerais state, Brazil, on seedling development of three native tropical forest species Psidium guajava L. (Myrtaceae), Citharexylum myrianthum Cham. (Verbenaceae), and Bixa orellana L. (Bixaceae). The method used to quantify thermal time influenced the analytical results of seedling development; the one that considered three cardinal temperatures and compared them with the mean air temperature (Method 5) performed better in computing thermal requirements. The influence of photoperiod on seedling development was inconclusive for the three species, but all three developed better in mild temperatures (between 13.3 °C and 26.9 °C) with a photoperiod shorter than 13 h. [ABSTRACT FROM AUTHOR]

Fine tuning crop development is a major breeding avenue to increase crop yield and for adaptation to climate change. We used an ecophysiological model that integrates our current understanding of the physiology of wheat phenology to predict the development and anthesis date of 91 recombinant inbreed lines (RILs) of durum wheat with genotypic parameters controlling vernalization requirement, photoperiod sensitivity, and earliness per se estimated using leaf stage, final leaf number, anthesis date data from a pot experiment with vernalized and nonvernalized treatments combined with short- and long-day length. Predictions of final leaf number and anthesis date of the QTL-based model was evaluated for the whole population of RILs in a set of independent field trials and for the two parents, which were not used to estimate the parameter values. Our novel approach reduces the number of environments and the time required to obtain the required data sets to develop a QTL-based prediction of model parameters. Moreover, the use of a physiologically based model of phenology gives new insight into genotype-phenology relations for wheat. We discuss the approach we used to estimate the parameters of the model and their association with QTL and major phenology genes that collocate at QTL. • Phenology is a key trait for plant adaptation to climate change. • Phenology parameters estimated under control condition experiments can be translated to the field. • Wheat phenology can be predicted by combining a process-based model with genomic information. • Future work should consider the development of spikelet primordium and floret. [ABSTRACT FROM AUTHOR]

ABSTRACT: This study assessed the nitrogen nutrition index, morphogenic characteristics and tiller structure of Alexandergrass (Urochloaplantaginea (LINK) Hitch) pasture submitted to different nitrogen (N) levels (zero, 150 or 300 kg ha-1 of N). The experimental design was entirely randomized with repeated measures arrangement. The experimental animals were Angus heifers under rotational stocking grazing method. The number of animals was variable to keep 30±5 cm post-grazing sward height. Nitrogen nutrition index increased linearly according N levels (Ŷ = 59.8 + 0.1216N; P < 0.0001; r²=0.53). The leaf appearance rate adjusted to a positive linear regression model according the thermal sum (TS) with zero of N (Ŷ0N = 0.0077 + 0.0000087TS; P = 0.0308; r² = 0.72) and 150 kg ha-1 of N (Ŷ150N = 0.0020 + 0.000021 TS; P = 0.0022; r² = 0.92). The use of 300 kg ha-1 of N did not alter the leaf appearance rate (0.0124 leaf degree-days-1). The use of up to 300 kg ha-1 of N increases the Alexandergrass nitrogen content. The leaf appearance rate in Alexandergrass is modified using N while the morphogenic characteristics leaf expansion, stem expansion, phyllochron, leaf lifespan, leaf elongation duration and tiller structure are not altered by N utilization.

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]

Despite recognizing the importance of genetic improvement in the production of barley grains, little information is available on the contribution of phenological development to the genetic improvement of Brazilian barley. Field experiments were carried out between 2011 to 2013, in the absence of biotic and abiotic stresses and with preventive lodging control. Five two-rowed spring barley cultivars, released between 1968 and 2008, were evaluated. Although there was no significant association in the cycle length (Emergence - Anthesis) of the cultivars with the year of release, the genetic improvement increased the proportion of the Doble ridge - Maximum number of spikelet primordia/Maximum number of spikelet primordia - anthesis period to the total time to anthesis. The period between DR-MNP was increased in modern cultivars, to the detriment of the Doble ridge - Maximum number of spikelet primordia period. However, the duration of the period between emergences to the double ridge (vegetative phase) was not altered in the analyzed period. Barley breeding in Brazil did not change the total number of leaves on the main stem but caused an increase in the number of leaves earlier in the development, favoring the high level of tillering. The leaf architecture of modern barley was altered towards a more vertical inclination (erectophilic canopy), allowing the penetration of photosynthetically active radiation into the crop canopy. [ABSTRACT FROM AUTHOR]

Despite recognizing the importance of genetic improvement in the production of barley grains, little information is available on the contribution of phenological development to the genetic improvement of Brazilian barley. Field experiments were carried out between 2011 to 2013, in the absence of biotic and abiotic stresses and with preventive lodging control. Five two-rowed spring barley cultivars, released between 1968 and 2008, were evaluated. Although there was no significant association in the cycle length (Emergence - Anthesis) of the cultivars with the year of release, the genetic improvement increased the proportion of the Doble ridge - Maximum number of spikelet primordia/Maximum number of spikelet primordia - anthesis period to the total time to anthesis. The period between DR-MNP was increased in modern cultivars, to the detriment of the Doble ridge - Maximum number of spikelet primordia period. However, the duration of the period between emergences to the double ridge (vegetative phase) was not altered in the analyzed period. Barley breeding in Brazil did not change the total number of leaves on the main stem but caused an increase in the number of leaves earlier in the development, favoring the high level of tillering. The leaf architecture of modern barley was altered towards a more vertical inclination (erectophilic canopy), allowing the penetration of photosynthetically active radiation into the crop canopy.

The branch construction of trees is based on phytomers, repetitive subunits defined as node + leaf + axillary meristem + internode. The rate at which phytomers are added to a shoot is termed the phyllochron, which is determined by genetics, endogenous regulation and environmental conditions. The phyllochron is fundamental to understanding the growth of plants. Most phyllochron studies on woody species are of young plants under controlled conditions without consideration for different types of shoots that are present in mature trees. In this 2-year field study, we investigated seasonal patterns of phyllochron development on both proleptic and epicormic shoots of mature peach trees (Prunus persica) exposed to two irrigation treatments. One treatment was not irrigated until significant stress was detected via water potential by pressure bombing. In the second treatment trees were normally irrigated with ~5.84 cm of water each week to match evapotranspirational loss. Midday stem water potential readings were regularly collected to assess the level of water stress experienced by the trees. Measurements of individual leaves and their corresponding internodes were taken along tagged proleptic and epicormic shoots three times per week from the beginning to the end of two growing seasons. Leaf measurements were used to calculate the phyllochron. The phyllochron increased as the season progressed. This increase could not be explained by traditionally accepted effects of temperature or light. The more vigorous epicormic shoots added leaves significantly faster than proleptic shoots on trees in both water deficit and normally irrigated treatments. Additionally, epicormic shoots produced leaves with significantly greater leaf length and leaf area. Midday stem water potentials were more negative in trees in the water deficit treatments only after proleptic shoots stopped growing. The phyllochron did increase while leaf length and leaf area decreased on epicormic shoots of deficit irrigated trees in the 2010 growing season. The phyllochron of both shoot types gradually increased over the season, which was primarily due to an endogenous rank or shoot ageing effect. Differences between shoot types indicate that the phyllochron is variable among shoots on the same tree and is associated with shoot vigour. Water deficit increased the phyllochron and over all shoot growth rate.

The plastochron, defined as the time interval between the initiations of two successive leaves, can also indicate the development of successive phytomers along a shoot. Previous work has shown that crop load impacts the plastochron in field-grown peach (Prunuspersica) trees, which led us to hypothesize that the plastochron of peach trees may be sensitive to the carbon status of the tree. To testthis hypothesis, a 38-day growth chamber study was conducted to determine if elevated CO2 (800 μmol·mol-1) speeds up the plastochron of young peach trees relative to their growth in ambient (400 μmol·mol-1) CO2. The leaf lamina lengths were measured every other day to generate leaf growth rate curves that were fitted against a classic Gompertz growth curve to estimate the time of the initiation of each leaf, which in turn, was used to estimate the plastochron. Additionally, in order to non-destructively gauge the effects of CO2 concentration on plant performance during the experiment, net leaf CO2 assimilation and stomatal conductance measurements were taken approximately half way through and at the end of the 38-day experiment. Doubling the ambient CO2 concentration had no effect on the plastochron, even though the leaf CO2 assimilation rates, leaf starch and total nonstructural carbohydrate concentrations were greater in trees grown in elevated CO2. In addition, there were no significant treatment differences in incremental shoot growth or the number of lateral syleptic shoots.

This study analyzes the dynamics of leaf and tiller emergence and development of widely spaced wheat sown on different dates. We used the phyllochron (time interval between the emergence of successive leaves at the same stage), site filling (the relative rate of increase in the number of tillers per phyllochron), and indices associated with ‘the synchronous growth’. Number of productive tillers per plant (including the main shoot, MS) reached 45.7 in early sowing, and significantly decreased by the delay in sowing. The increase in tiller number with the elapse of leaf age (Haun stage) of MS (HSms) was almost the same as that expected from synchronous growth until HSms 8.6 and site filling before this HSms was close to 0.481. The phyllochron was shortest in MS and increased in axillary tillers with increasing tiller order and position, but the differences in phyllochron between MS and axillary tillers within a plant were significant only at higher order and positions of tillers. The time of emergence of tillers was always advanced in comparison with that expected from synchronous growth. A very close negative linear relationship was found between the number of days from emergence to heading of tillers and the time of their emergence expressed as day of year; this relationship was independent of the tiller order, position and sowing date. Although the phyllochron gradually became longer, a progressive decrease of the leaf and spikelet per spike with the increasing tiller order and position may contribute considerably to the convergence to heading time.

The relationship between collared leaf number and growing degree days (GDD) is crucial for predicting maize phenology. Biophysical crop models convert GDD accumulation to leaf numbers by using a constant parameter termed phyllochron (°C-day leaf−1 ) or leaf appearance rate (LAR; leaf o C-day−1 ). However, such important parameter values are rarely estimated for modern maize hybrids. To fill this gap, we sourced and analyzed experimental datasets from the United States Corn Belt with the objective to (i) determine phyllochron values for two types of models: linear (1-parameter) and bilinear (3-parameters; phase I and II phyllochron, and transition point) and (ii) explore whether environmental factors such as photoperiod and radiation, and physiological variables such as plant growth rate can explain variability in phyllochron and improve predictability of maize phenology. The datasets included different locations (latitudes between 48° N and 41° N), years (2009–2019), hybrids, and management settings. Results indicated that the bilinear model represented the leaf number vs. GDD relationship more accurately than the linear model (R2=0.99 vs. 0.95, n=4,694). Across datasets, first phase phyllochron, transition leaf number, and second phase phyllochron averaged 57.9±7.5°C-day, 9.8±1.2 leaves, and 30.9±5.7°C-day, respectively. Correlation analysis revealed that radiation from the V3 to the V9 developmental stages had a positive relationship with phyllochron (r=0.69), while photoperiod was positively related to days to flowering or total leaf number (r=0.89). Additionally, a positive nonlinear relationship between maize LAR and plant growth rate was found. Present findings provide important parameter values for calibration and optimization of maize crop models in the United States Corn Belt, as well as new insights to enhance mechanisms in crop models. [ABSTRACT FROM AUTHOR]

The relationship between collared leaf number and growing degree days (GDD) is crucial for predicting maize phenology. Biophysical crop models convert GDD accumulation to leaf numbers by using a constant parameter termed phyllochron (°C-day leaf−1) or leaf appearance rate (LAR; leaf oC-day−1). However, such important parameter values are rarely estimated for modern maize hybrids. To fill this gap, we sourced and analyzed experimental datasets from the United States Corn Belt with the objective to (i) determine phyllochron values for two types of models: linear (1-parameter) and bilinear (3-parameters; phase I and II phyllochron, and transition point) and (ii) explore whether environmental factors such as photoperiod and radiation, and physiological variables such as plant growth rate can explain variability in phyllochron and improve predictability of maize phenology. The datasets included different locations (latitudes between 48° N and 41° N), years (2009–2019), hybrids, and management settings. Results indicated that the bilinear model represented the leaf number vs. GDD relationship more accurately than the linear model (R2 = 0.99 vs. 0.95, n = 4,694). Across datasets, first phase phyllochron, transition leaf number, and second phase phyllochron averaged 57.9 ± 7.5°C-day, 9.8 ± 1.2 leaves, and 30.9 ± 5.7°C-day, respectively. Correlation analysis revealed that radiation from the V3 to the V9 developmental stages had a positive relationship with phyllochron (r = 0.69), while photoperiod was positively related to days to flowering or total leaf number (r = 0.89). Additionally, a positive nonlinear relationship between maize LAR and plant growth rate was found. Present findings provide important parameter values for calibration and optimization of maize crop models in the United States Corn Belt, as well as new insights to enhance mechanisms in crop models.

The objective of this study was to characterize the development of chia plants sown at different dates, and to determine the relation between the duration of the development cycle and the final number of leaves and the leaf appearance rate on the main stem. A field experiment was conducted in the agricultural year of 2016/2017 in five sowing dates (09/22/16, 10/28/16, 01/03/17, 02/08/17 and 03/24/17) in the edaphoclimatic conditions of the central region of the RS, Brazil. A randomized block design with four replicates was used. For each sowing date, the duration of the vegetative and reproductive phases in days and in °C day (Tb = 11 °C), the final number of leaves and the phyllochron of the main stem were determined. The duration of the vegetative phase of chia plants in days and in °C day varies between the sowing dates, with shorter duration in late sowings in response to the photoperiod reduction. The vegetative phase represents the largest part of the total development cycle in early sowing dates, being overcome by the reproductive phase in late sowing dates (02/08/17 and 03/24/17). The phyllochron for chia varies from 36.23 (very late sowing) to 59.88 °C day (early sowing). Later sowing has a smaller final number of leaves accumulated in the main stem due to the shorter duration of the vegetative phase. [ABSTRACT FROM AUTHOR]

The effects of four deferred grazing strategies (30, 60, 90 and 120 days) on morphogenic and structural characteristics, herbage accumulation, and chemical composition of signal grass (Brachiaria brizantha cv. Xaraés) were evaluated. The experiment was conducted in Rondonópolis, Mato Grosso, Brazil, during the transition period between the rainy and the dry season, from April to August 2013. The number of live leaves and leaf lifespan were quadratically affected (p < 0.05) by the period of deferment. Pasture height linearly increased (p < 0.05) with increasing deferment periods, reaching a maximum of 54.33 cm at 120 d of deferment. The leaf: stem ratio linearly increased (p < 0.05) with increasing deferment periods and remained higher than 1 during all evaluation periods. Total dry matter accumulation increased linearly (p < 0.05), with an average of 7817 kg/ha at day 120 of the deferment. Concentrations of crude protein and neutral detergent fiber were not affected by the length of the deferment period (p < 0.05). A deferment period of up to 120 days resulted in increased dry matter accumulation, a higher leaf: stem ration, and only slight changes in the structural characteristics and chemical composition of Xaraés pasture grass. [ABSTRACT FROM AUTHOR]

To examine the interactive effect of temperature and photon flux density (PFD) on growth dynamics and gas exchange of young Vitis vinifera L. cv. Shiraz vines, a controlled environment study was conducted by exposing vines to two different temperatures combined with either high or low PFD. Shoot growth was accelerated and the phyllochron of Shiraz leaves was hastened in the low temperature (25/12°C) × low PFD condition (350 μmol m−2 s−1). In early emerging leaves, leaf area was responsive to temperature whereas in later emerging leaves it was dependent on light intensity. The high temperature (32/20°C) × high PFD (700 μmol m−2 s−1) treatment delayed internode extension of early emerging internodes. However, low temperature × high PFD increased leaf gas exchange across the different growth stages. The net shoot carbon balance was greater for the low temperature × high PFD treatment. Dry matter accumulation was also greater in early emerging internodes irrespective of treatment. These results on young Shiraz vines indicate that 25°C is favourable to 32°C, and some growth characteristics are accelerated at low PFD while others favour higher PFD. This study describes the effects of temperature and light combination on young Vitis vinifera L. cv. Shiraz vines. The low temperature and low or high light conditions are favourable for growth characters of young vegetative Shiraz vines. However, high temperature and high light conditions are detrimental. [ABSTRACT FROM AUTHOR]

Temperature affects plant development therefore phyllochron has been used as a predictor for developmental events to define the time for agricultural managing practices. This study aims to evaluate changes in phyllochron and thermal sum required for flowering by oat genotypes developed at different decades at three temperature regimes; the effect of high temperature on phytomere development; and identify the development stage at the moment of meristem transition to reproductive stage. Three environments were obtained by sowing in the fall, in the spring, and under constant temperature (17oC), always at inductive photoperiod. Despite changes in nominal values small differences were found among genotypes' phyllochron. Adding specific optimal and maximum temperatures into the growing degree days' calculation demonstrated phyllochron stability among environments. Plant cycle length and thermal sum correlated with the number of developed phytomeres. UFRGS 078030-2 plants flowered earlier, had a small number of phytomeres, and greater tolerance to elevated temperatures than the other genotypes. More recent genotypes transit to reproductive stage at an earlier Haun stage than older ones. [ABSTRACT FROM AUTHOR]

A less‐explored alternative to animal production in the subtropics is a mixture of perennial cool‐ and warm‐season forage grasses. This study aimed to determine a grazing management strategy to enhance forage production and attenuate the seasonality of a mixed pasture composed of kikuyugrass (Pennisetum clandestinum) and tall fescue (Festuca arundinacea). Four treatments were implemented in a completely randomized block design using a factorial scheme (2 × 2) with three replicates. The factorial arrangement consisted of two canopy heights (12 and 17 cm) associated with or without a single autumn grazing of 7 cm. Evaluations were conducted over 2 years. Nitrogen fertilization was performed only during the winter and spring seasons. Regardless of grazing height targets (12 or 17 cm), severe defoliation in autumn increased forage accumulation by 10% in mixed pastures composed of kikuyugrass and tall fescue; however, such management strategy should not be recommended because it delayed canopy recovery by 90–120 days, restrained winter grazing, and, paradoxically, increased forage production seasonality. Tall fescue was the dominant species in all treatments in the second year of evaluation, and we hypothesized that the lack of N fertilization during the summer impaired the persistence of kikuyugrass and was the main reason for this dominance effect. Therefore, we suggest evaluating summer N fertilization strategies, which could benefit both species and ensure the persistence of kikuyugrass in the mixture. [ABSTRACT FROM AUTHOR]

ABSTRACT: Temperature affects plant development therefore phyllochron has been used as a predictor for developmental events to define the time for agricultural managing practices. This study aims to evaluate changes in phyllochron and thermal sum required for flowering by oat genotypes developed at different decades at three temperature regimes; the effect of high temperature on phytomere development; and identify the development stage at the moment of meristem transition to reproductive stage. Three environments were obtained by sowing in the fall, in the spring, and under constant temperature (17oC), always at inductive photoperiod. Despite changes in nominal values small differences were found among genotypes’ phyllochron. Adding specific optimal and maximum temperatures into the growing degree days’ calculation demonstrated phyllochron stability among environments. Plant cycle length and thermal sum correlated with the number of developed phytomeres. UFRGS 078030-2 plants flowered earlier, had a small number of phytomeres, and greater tolerance to elevated temperatures than the other genotypes. More recent genotypes transit to reproductive stage at an earlier Haun stage than older ones.

The present study was carried out to monitor leaf growth, foliar emission, and the daily photosynthesis behavior of sisal plants cv Ceniza. In a commercial crop, sisal plants were selected and monitored weekly to determine increase in number, length, width, and thickness of the leaves, during a 154 day period. On two occasions during the experimental period, gas exchange rates were also monitored during the light and dark periods. The results allowed determining a phyllochron of 8.65 days. Gas exchange monitoring detected low stomatal conductance rates during the light period. However, starting at 15:30 h, stomatal conductance substantially increased, remaining at maximum levels throughout the dark period, and, subsequently, decreased from 09:30 h, the following light period. A high correlation of stomatal conductance with vapor pressure deficit and leaf temperature was found. Maximum CO2 fixation rates varied between 12.2 and 14.5 µmol m-2 s-1, recorded between 19:19 and 19:26 h. The results corroborate the CAM metabolism of sisal plants cv Ceniza. [ABSTRACT FROM AUTHOR]

This study analyzes the dynamics of leaf and tiller emergence and development of widely spaced wheat sown on different dates. We used the phyllochron (time interval between the emergence of successive leaves at the same stage), site filling (the relative rate of increase in the number of tillers per phyllochron), and indices associated with 'the synchronous growth'. Number of productive tillers per plant (including the main shoot, MS) reached 45.7 in early sowing, and significantly decreased by the delay in sowing. The increase in tiller number with the elapse of leaf age (Haun stage) of MS (HSms) was almost the same as that expected from synchronous growth until HSms 8.6 and site filling before this HSms was close to 0.481. The phyllochron was shortest in MS and increased in axillary tillers with increasing tiller order and position, but the differences in phyllochron between MS and axillary tillers within a plant were significant only at higher order and positions of tillers. The time of emergence of tillers was always advanced in comparison with that expected from synchronous growth. A very close negative linear relationship was found between the number of days from emergence to heading of tillers and the time of their emergence expressed as day of year; this relationship was independent of the tiller order, position and sowing date. Although the phyllochron gradually became longer, a progressive decrease of the leaf and spikelet per spike with the increasing tiller order and position may contribute considerably to the convergence to heading time. [ABSTRACT FROM AUTHOR]

Simulating leaf development from initiation to maturity opens new possibilities to model plant–environment interactions and the plasticity of plant architecture. This study analyses the dynamics of leaf production and extension along a maize (Zea mays) shoot to assess important modelling choices. Maize plants from two cultivars originating from the same inbred line, yet differing in the length of mature leaves were used in this study. We characterized the dynamics of the blade and sheath lengths of all phytomers by dissecting plants every 2–3 days. We analysed how differences in leaf size were built up and we examined the coordination between the emergence of organs and phases of their extension. Leaf extension rates were higher in the cultivar with longer leaves than in the cultivar with shorter leaves; no differences were found in other aspects. We found that (i) first post-embryonic leaves were initiated at a markedly higher rate than upper leaves; (ii) below ear position, sheaths were initiated at a time intermediate between tip emergence and appearance, while above the ear position, sheaths were initiated at a high rate, such that the time interval between the blade and sheath initiations decreased for these leaves; and (iii) ear position also marked a change in the correlation in size between successive phytomers with little correlation of size between upper and lower leaves. Our results identified leaf extension rate as the reason for the difference in size between the two cultivars. The two cultivars shared the same pattern for the timing of initiation events, which was more complex than previously thought. The differences described here may explain some inaccuracies reported in functional–structural plant models. We speculate that genotypic variation in behaviour for leaf and sheath initiation exists, which has been little documented in former studies. [ABSTRACT FROM AUTHOR]

Background and Aims The dynamics of plant architecture is a central aspect of plant and crop models. Most models assume that whole shoot development is orchestrated by the leaf appearance rate, which follows a thermal time schedule. However, leaf appearance actually results from leaf extension and taking it as an input hampers our ability to understand shoot construction. The objective of the present study was to assess a modelling framework for grasses, in which the emergence of leaves and other organs is explicitly calculated as a result of their extension. Methods The approach builds on a previous model, which uses a set of rules co-ordinating the timing of development within and between phytomers. We first assessed rule validity for four experimental datasets, including different cultivars, planting densities and environments, and accordingly revised the equations driving the extension of the upper leaves and of internodes. We then fitted model parameters for each dataset and evaluated the ability to simulate the measured phenotypes across time. Finally, we carried out a sensitivity analysis to identify the parameters that had the greatest impact and to investigate model behaviour. Key Results The modified version of the model simulated correctly the contrasting maize phenotypes. Co-ordination rules accounted for the observations in all studied cultivars. Factors with major impact on model output included extension rates, the time of tassel initiation and initial conditions. A large diversity of phenotypes could be simulated. Conclusions This work provides direct experimental evidence for co-ordination rules and illustrates the capacity of the model to represent contrasting phenotypes. These rules play an important role in patterning shoot architecture and some of them need to be assessed further, considering contrasting growth conditions. To make the model more predictive, several parameters could be considered in the future as internal variables driven by plant status. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the morphogenetic and structural characteristics of Brachiaria brizantha cv. marandu subjected to grazing management strategies. The treatments corresponded to four grazing management strategies (25-10; 25-15; 35-15; and 45-15 pre and post grazing swards heights, respectively). Grazing management strategies were allocated to the experimental units (100 m2 paddocks) in a completely randomized blocks design with four repetitions. There was no effect of the grazing management on leaf elongation rate and leaf senescence rate, with average values of 11.22 mm/day and 2.17 mm/day, respectively. There were significant differences (p < 0.05) of leaf appearance rate, leaf elongation rate and stem elongation rate among months, where higher values were seen in months with greater rainfall. The evaluated management strategies showed a small effect on the morphogenetic and structural characteristics and can consequently be utilized for the management of marandu grass. In addition, during rainy periods, farmers can use management with higher defoliation frequencies (25-15), while the opposite (45-15) may be used during months with low rainfall in order not to exhaust the organic reserves of the plant. [ABSTRACT FROM AUTHOR]

Wheat adaptation can be fine-tuned by earliness per se (Eps) genes. Although the effects of Eps genes are often assumed to act independently of the environment, previous studies have shown that they exhibit temperature sensitivity. The number of leaves and phyllochron are considered determinants of flowering time and the numerical components of yield include spikelets per spike and fertile floret number within spikelets. We studied the dynamics of leaf, spikelet, and floret development in near isogenic lines with either late or early alleles of Eps - D1 under seven temperature regimes. Leaf appearance dynamics were modulated by temperature, and Eps alleles had a greater effect on the period from flag leaf to heading than phyllochron. In addition, the effects of the Eps alleles on spikelets per spike were minor, and more related to spikelet plastochron than the duration of the early reproductive phase. However, fertile floret number was affected by the interaction between Eps alleles and temperature. So, at 9 °C, Eps -early alleles had more fertile florets than Eps -late alleles, at intermediate temperatures there was no significant difference, and at 18 °C (the highest temperature) the effect was reversed, with lines carrying the late allele producing more fertile florets. These effects were mediated through changes in floret survival; there were no clear effects on the maximum number of floret primordia. [ABSTRACT FROM AUTHOR]

Effect of thermo-photoperiod conditions on pre-flowering phasic development, number of unfolded leaves, verticillaster dry weight at flowering (VDWFL) and grain yield were evaluated for chia (Salvia hispanica L.). The objectives of this study were to: (i) characterise the pre-flowering response of chia to thermo-photoperiod conditions during and pre- and post-inductive subphases; and (ii) determine the relationships between the duration of pre-flowering subphases, the VDWFL and grain yield. Sowing-date experiments were conducted during three consecutive growing seasons with two chia genotypes under non-stressed conditions. Responses to thermo-photoperiod conditions were characterised by fitting a bi-linear model. All pre-flowering subphases showed a quantitative short-day response with a decrease in sensitivity to photoperiod in the later post-inductive subphase. The duration of the pre-inductive subphase was associated with the number of accumulated unfolded leaves, whereas the durations of the post-inductive subphases were not determined by the number of accumulated unfolded leaves. Higher VDWFL was achieved when durations of the pre-flowering subphases increased. In addition, increases in the VDWFL explained most of the variation in grain yield along the thermo-photoperiod conditions. Accordingly, this study suggests that developmental responses of chia and their relationships with VDWFL and grain yield should be taken into account for grain-yield improvement of this orphan crop. Chia is a revalorised, orphan grain crop rich in omega-3, and is important as a food and for prevention of cardiovascular afflictions. This study characterised the developmental responses of chia in order to establish management and breeding strategies in different environments. Results suggest that developmental responses are associated with yield subcomponents; application of this knowledge could lead to increases in yield. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work was to estimate cardinal temperatures and phyllochron for the leaf development of the eucalyptus species Corymbia citriodora and Eucalyptus urophylla, in the seedling phase. A field experiment was carried out in a completely randomized design, in a 2x11 factorial arrangement, with the two eucalyptus species, 11 sowing dates, and five replicates, in the municipality of Itajubá, in the state of Minas Gerais, Brazil. The cardinal temperatures - base, optimum, and maximum - for leaf development were, respectively, 8.7, 17.1, and 41.3°C, for C. citriodora, and 11.5, 17.1, and 40.5°C for E. urophylla. The phyllochron of C. citriodora was 62.95°C day per leaf, and that of E. urophylla was 46.03°C day per leaf, which indicates that E. urophylla requires less energy accumulation than C. citriodora for leaf emission in the main stem.

Abstract: The objective of the study was to evaluate the growth and production efficiency of forage-grain dual-purpose wheat in two arrangements and four agroforestry systems (Intercrop-I and Intercrop-II), as well as to evaluate crop management for the wheat crops in two planting seasons (Crop Season I-2014 and Crop Season II-2015. The experiment was conducted in a randomized complete block design, factorial scheme 7x2x2, with seven cultivation systems Eucalyptus urophylla x Eucalyptus grandis Intercrop-II and Intercrop-I; Peltophorum dubium Intercrop-II and Intercrop-I; P. rigida Intercrop-I; S. parahyba Intercrop-I; a wheat monoculture with no tree species present; and two harvest management techniques (with and without harvesting of the forage species). Agroforestry systems generated shading for wheat plants, with a higher phyllochron and lower values of leaf area index of those individuals kept under trees with higher crown shading (non-deciduous trees) due to the lower transmissivity of solar radiation. The systems composed with Schizolobium parahyba in Intercrop-I and Parapiptadenia rigida in Intercrop-I provide a minor phyllochron to the wheat, resulting in a higher leaf area index and dry matter yield. Thus, the cultivation of tree species and dual-skilled agricultural crops, such as wheat, provides promising alternatives for the future use of land in tropical countries.

• Camarosa and Albion show similarity in only four of the 24 characteristics evaluated by the descriptors. • New structure is identified in strawberry cultivars. • It is suggested that the new structure has the function to protect the flower bud and inflorescence. • The Albion cultivar can be more effective in absorbing water and nutrients by the root system being more profuse. The strawberry has already been described, but rarely based on the descriptors of the culture, which is relevant to knowledge of the morphology in their cultivation habitat. The objective of this work was to describe morphologically two strawberry cultivars based on the descriptors of the species and evaluate if there are differences in morphological performance between them when cultivated in protected environment and their responses to morphophenology. The treatments were the strawberry cultivars: Albion (Day-Neutral) and Camarosa (Short-Day), organized in a completely randomized design, with 20 replicates. This work was developed in part as a descriptive research (morphological performance) and part as explanatory research (morphophenology performance). In the descriptive research, were analyzed the morphological performance of the cultivars, based on the morphological descriptors, being the data presented in a descriptive form. In the explanatory research, were analyzed the morphophenology of the two cultivars, being the data submitted to analysis of variance and Tukey test at 5% probability of error. Albion and Camarosa showed similarity in only four characteristics of the 24 evaluated by the descriptors and both had the presence of a botanical structure called hypsophyll. The cultivars presented a morphologically distinct root system, Albion presented a better root system, with deeper roots. Albion was more effective in emitting leaves. It is concluded that both strawberry cultivars, with different photoperiodic responses, presented a botanical structure denominated hypsophyll, which is not included in the morphological descriptors for this species. In addition, Albion is possibly more effective in absorbing water and nutrients, because it has a more extensive root system. [ABSTRACT FROM AUTHOR]

Accurate predictions of the timing of physiological stages and the development rate are crucial for predicting crop performance under field conditions. Plant development is controlled by the leaf appearance rate (LAR) and our understanding of how LAR responds to environmental factors is still limited. Here, we tested the hypothesis that carbon availability may account for the effects of irradiance, photoperiod, atmospheric CO2 concentration, and ontogeny on LAR. We conducted three experiments in growth chambers to quantify and disentangle these effects for both winter and spring wheat cultivars. Variations of LAR observed between environmental scenarios were well explained by the supply/demand ratio for carbon, quantified using the photothermal quotient. We therefore developed an ecophysiological model based on the photothermal quotient that accounts for the effects of temperature, irradiance, photoperiod, and ontogeny on LAR. Comparisons of observed leaf stages and LAR with simulations from our model, from a linear thermal-time model, and from a segmented linear thermal-time model corrected for sowing date showed that our model can simulate the observed changes in LAR in the field with the lowest error. Our findings demonstrate that a hypothesis-driven approach that incorporates more physiology in specific processes of crop models can increase their predictive power under variable environments. [ABSTRACT FROM AUTHOR]

Highlights • Inoculation with specific rhizobia increased lucerne yield in N-deficient soils. • Spring sowing promoted faster establishment and higher above and below ground yields. • Higher yields for inoculated treatments were linked to increased leaf area, N fixation and higher RUE shoot. • Lower yields in late sowings were associated with decreased RUE shoot and longer phyllochrons, indicating carbon demand to roots. • The inoculation effect was temporary and uninoculated plants established effective nodulation over time. Abstract This study analysed the effects of sowing dates and inoculation treatments on yield components of rainfed lucerne (Medicago sativa L.) crops grown at Lincoln University, New Zealand. Crops were sown in a split-plot design on 26 January, 21 February, 15 March and 3 April 2012, combined with five inoculation treatments (ALOSCA®, coated seed, Nodulator®, peat slurry and bare seed). Shoot biomass was 90% higher in the earliest spring sowing date (19.8 ± 0.14 t ha−1) compared with the latest (11.9 ± 0.15 t ha−1). Yield variability was explained by differences in light interception and its conversion efficiency (RUE shoot) in the first spring. A 40% reduction in RUE shoot was estimated for March and April (autumn) sowing (0.93 ± 0.05). This was probably caused by greater continued partitioning of biomass to roots. A longer phyllochron for autumn sowing reduced leaf area expansion rates. Root biomass was higher from early sowing dates, but by the end of the experiment all treatments had >3 t ha−1 of perennial biomass. Inoculation increased shoot yield by 40% compared with the uninoculated control (16.6 ± 0.1 vs. 13 ± 0.2) in the first year. Bare seed treatments fixed 50% less nitrogen during the winter and early spring of 2012. This was linked to less nodulation and reduced nitrogen nutrition index (NNI) in shoots of the uninoculated treatment. However, after late spring, nitrogen fixation was not different among treatments, which was consistent with effective colonisation by naturalized rhizobia strains in the bare seed treatment. A 20% decrease in RUE shoot was measured in uninoculated crops compared with inoculated ones. This was probably caused by reduced photosynthesis due to the lower NNI. Root biomass was unaffected by inoculation and all treatments reached >3. t ha−1 by the end of the experiment. Uninoculated lucerne crops appeared to have similar accumulation rates of perennial biomass despite lower N fixation and N content in shoots. These results explain the physiological response of lucerne crops to sowing date and inoculation and can be used to inform management decisions and crop simulation models. [ABSTRACT FROM AUTHOR]

The objectives of the experiment were to (i) examine the dynamics of WSC use and the recovery of leaf sheaths and blades of Bromus valdivianus Phil. and Lolium perenne L. subjected to two defoliation frequencies (DFs) determined by thermal time (TT); (ii) evaluate how DF influenced regrowth and accumulated herbage mass (AHM) during fall. Defoliation was carried out at frequencies of 135 and 270 accumulated growing degree days (AGDDs) for both species. Twelve plots were arranged in a three-block design. All plots had a conditioning period to establish the assigned DF prior to sampling. From the start of the experiment, “cores” were collected from each plot every three days until the DF was reached. Every core was separated into leaf and sheath material before measuring the WSC concentration. Lolium perenne had concentrated more WSCs than B. valdivianus. Both species adapted their WSC recovery according to the DF. The recovery of WSC was faster under a DF of 135 AGDDs than that of 270 AGDDs. Leaf sheaths contained more WSCs than leaf blades and were identified as WSC storage organs. This period can be used as the optimal defoliation interval in B. valdivianus and L. perenne grazing systems.

The herbage mass and nutritional value of harvested forage are fundamental determinants of the production potential of pastoral systems. The objective of this study was to evaluate the growth dynamics and accumulated herbage mass expressed in dry matter (DM) of perennial ryegrass (Lolium perenne L.) and pasture brome (Bromus valdivianus Phil.) pastures, using thermal time (TT) as a defoliation criterion. Thirty plots (15 of L. perenne and 15 of B. valdivianus) were distributed in three field blocks and subjected to five defoliation frequencies (DF) determined by TT, expressed as the accumulated growing degree-days (AGDD; DF1 = 90, DF2 = 180, DF3 = 270, DF4 = 360, and DF5 = 450 AGDD) for one year (2016), at the Austral Agricultural Experimental Station of the Universidad Austral de Chile. Every three days, the total leaf length (TLL) was measured, and the leaf elongation rate (LER, cm L−1), leaf growth rate (LGR, cm L−1), leaf appearance rate (LAR, d L−1), phyllochron (AGDD L−1), and accumulated herbage mass per hectare (kg DM ha−1) were calculated. Defoliations were scheduled according to AGDD, and a sample was taken from each cutting to determine (dry matter ‘DM’, crude protein ‘CP’, neutral detergent fiber ‘NDF’, acid detergent fiber ‘ADF’, water-soluble carbohydrates ‘WSC’ and metabolizable energy ‘ME’). The pastures that were allocated to DF5 presented higher DM yields (12,600 kg DM ha−1 year−1), TLL (54.6 cm), and LER (0.63 cm d−1) compared to pastures with high DF (90 and 180 ADGG). B. valdivianus presented a lower phyllochron than L. perenne (74.4 vs 87.9 AGDD L−1, respectively). Concentrations of CP and ME decreased from the shortest DF (90 AGDD) to the largest DF (450 AGDD), dropping from 221 to 138 g kg−1 CP and from 2.6 to 2.4 Mcal kg−1 DM of ME. All variables were affected by the season (Ssn) (p < 0.001). The AGDD can be used as a defoliation criterion and a tool to balance yield with nutritive value according to the farmer’s needs.

In order to study the effects of nitrogen application rate and timing on grain yield, phyllochron and leaf appearance rate of corn (Zea mays L.), an experiment was conducted as split plot based on randomized complete block design with three replications at the Research Farm of University of Mohaghegh Ardabili, Ardabil, Iran during 2009 growing season. Nitrogen rates were arranged in main plot with four levels including: 0, 75, 150 and 225 Kg N ha-1 and nitrogen application timing in sub plots at three levels: (1/3 in planting + 1/3 in 8-10 leaf stages + 1/3 in tasseling), (½ planting + ½ in tasseling) and (½planting + ¼ in 8-10 leaf stages + ¼ in tasseling) as T1, T2 and T3 respectively. The results showed that phyllochron was significantly affected by nitrogen rate, application timing and interaction of rate × nitrogen application timing. Phyllochron was decreased with increasing nitrogen rates, but the reverse was true for leaf appearance rate. Leaf appearance rate in T1 nitrogen application was more than the other methods. The highest leaf appearance rate and the least phyllochron belonged to treatment of 225 Kg N ha-1 and T1 nitrogen application timing. The highest grain yield (7928.6 Kg ha-1) belonged to treatment of 225 Kg N ha-1 and T1 nitrogen application timing. Thus, it seems that in order to increase the grain yield and leaf appearance rate, 225 Kg N ha-1 should be applied as T1 in conditions of Ardabil climate.

In this paper, we address the change-point estimation issue in multivariate observations which consist in functions having piecewise constant first derivatives corrupted by some additional noise. We propose to solve this problem by rewriting it as a variable selection issue in a sparse multivariate linear model. Moreover, the methodology that we propose takes into account the dependence that may exist within the multivariate observations. Then, the performance of our approach is assessed through some numerical experiments and compared to other alternative and classical methods. Finally, we apply our methodology to experimental data in order to study the vegetative development of oilseed rape. The evolution of the number of leaves of oilseed rape can be modeled as a function having piecewise constant first derivatives corrupted by some additional noise where the change-points correspond to key times in the plant phenology. Our novel estimation method increases the accuracy of the change-point estimation in comparison with classical approaches. Moreover, we show that the parameters of the covariance matrix depend on the level of competition between plants. Supplementary materials accompanying this paper appear online. [ABSTRACT FROM AUTHOR]

Earliness per se ( Eps ) genes are critical for fine-tuning flowering time and likely to modify other developmental traits as well. Effects of Eps alleles on components comprising flowering time of hexaploid wheat have not been studied. In this work, we evaluated under field conditions the effects of Eps alleles on flowering time and on a number of developmental traits using four groups of near isogenic lines (NILs) with contrasting Eps alleles (late vs early alleles). The NIL groups were derived from the Avalon x Cadenza (AxC) cross with the Eps effects on either chromosome 1D or 3A and from the Spark x Rialto (SxR) cross with the Eps effect on chromosome 1D. Eps-D1 -late alleles delayed flowering (and the effect was stronger in AxC than in SxR); while Eps 3A did not have any effect. Differences in flowering time between NILs with Eps-D1 -early and –late alleles were mainly associated with the effects of this gene on the duration of the late reproductive phase consistently for both crosses. However, the effects of Eps-D1 on other developmental traits were different depending on the specific cross used to produce the NILs. The Eps-D1 -early allele from AxC did not affect FLN, reduced spikelet initiation phase and, in turn, decreased the spikelet number (though less than proportionally as it accelerated the rate of spikelet initiation as well), whilst Eps-D1 -early allele from SxR affected marginally FLN, but had no effects on either spikelet initiation phase or spikelet number. The results reported from this study in Mediterranean conditions conflict quantitatively ( Eps-D1 ) or qualitatively ( Eps 3A ) with results observed previously in the UK, likely evidencing the existence of Eps x temperature interactions. [ABSTRACT FROM AUTHOR]

* Background and Aims Dynamics in branch and leaf growth parameters, such as the phyllochron, duration of leaf expansion, leaf life span and bud mortality, determine tree architecture and canopy foliage distribution. We aimed to estimate leaf growth parameters in adult Arabica coffee plants based on leaf supporter axis order and position along the vertical profile, considering their modifications related to seasonal growth, air [CO2] and water availability. * Methods Growth and mortality of leaves and terminal buds of adult Arabica coffee trees were followed in two independent field experiments in two sub-tropical climate regions of Brazil, Londrina-PR (Cfa) and Jaguariúna-SP (Cwa). In the Cwa climate, coffee trees were grown under a FACE (free air CO2 enrichment) facility, where half of those had been irrigated. Plants were observed at a 15-30 d frequency for 1 year. Leaf growth parameters were estimated on five axes orders and expressed as functions of accumulated thermal time (°Cd per leaf). * Key Results The phyllochron and duration of leaf expansion increased with axis order, from the seond to the fourth. The phyllochron and life span during the reduced vegetative seasonal growth were greater than during active growth. It took more thermal time for leaves from the first- to fourth-order axes to expand their blades under irrigation compared with rainfed conditions. The compensation effects of high [CO2] for low water availability were observed on leaf retention on the second and third axes orders, and duration of leaf expansion on the first- and fourth-order axes. The second-degree polynomials modelled leaf growth parameter distribution in the vertical tree profile, and linear regressions modelled the proportion of terminal bud mortality. * Conclusions Leaf growth parameters in coffee plants were determined by axis order. The duration of leaf expansion contributed to phyllochron determination. Leaf growth parameters varied according the position of the axis supporter along the vertical profile, suggesting an effect of axes age and micro-environmental light modulations. [ABSTRACT FROM AUTHOR]

Triploid Miscanthus × giganteus (Greef et Deu. ex Hodkinson et Renvoize) is a sterile, perennial grass used for biomass production in temperate environments. While M. × giganteus has been intensively researched, a scale standardizing description of M. × giganteus morphological stages has not been developed. Here we provide such a scale by adapting the widely-used Biologische Bundesanstalt, Bundessortenamt, CHemische Industrie (BBCH) scale and its corresponding numerical code to describe stages of morphological development in M. × giganteus using observations of the “Freedom” and “Illinois” clone in Iowa, USA. Descriptive keys with images are also presented. Because M. × giganteus plants overlap in the field, the scale was first applied to individual stems and then scaled up to assess plants or communities. Of the 10 principal growth stages in the BBCH system, eight were observed in M. × giganteus. Each principal stage was subdivided into secondary stages to enable a detailed description of developmental progression. While M. × giganteus does not have seed development stages, descriptions of those stages are provided to extend the scale to other Miscanthus genotypes. We present methods to use morphological development data to assess phenology by calculating the onset, duration, and abundance of each developmental stage. This scale has potential to harmonize previously described study-specific scales and standardize results across studies. Use of the precise staging presented here should more tightly constrain estimates of developmental parameters in crop models and increase the efficacy of timing-sensitive crop management practices like pest control and harvest.