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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.

A study was conducted during 2012–2014 in carbondioxide temperature gradient tunnels (CTGTs) and in ambient condition to assess the interaction effect of elevated carbondioxide and temperature in two genotypes of Capsicum chinense Jacq. on some developmental processes. The treatments consisted of field (ambient CO2 and ambient temperature), CTGT I (380 ppm CO2 and ambient temperature), CTGT II (550 ppm CO2 with ambient temp. + 2 °C elevation) and CTGT III (750 ppm CO2 with ambient temp. + 4 °C elevation). Elevated CO2 and temperature brought about a significant difference in phyllochron index and leaf number in both the years. A lower phyllochron or higher leaf emission rate was reported in cv. Manipur over cv. Assam. A variation among the species was also observed in the present experiment where days to anthesis was much more accelerated in cv. Manipur than that of cv. Assam. There was a significant difference in days to anthesis between the cultivars, treatments and interaction of treatments and cultivars. A significant difference in number of fruit/plant was noted amongst the treatments and among the cultivars in both the years. This indicates the responses of genotypes under future climate change conditions.

Crop load or carbohydrate availability, affects the phyllochron, leaf length, and leaf area of proleptic and epicormic shoots on mature, field-grown Prunus persica trees. It is well known that shoot growth rates can be strongly influenced by availability of carbohydrates to support growth. Additionally, carbohydrate availability for vegetative growth is influenced by crop load, since fruits are strong sinks for photosynthates. Thus, while crop load is known to have significant effects on shoot growth rates it is not clear whether this effect is limited to extension growth rates of internodes or whether it also affects shoot development such as the rate at which nodes are added to shoots, i.e., the phyllochron. In this study, we investigated the effect of the presence and absence of the crop on the phyllochron of proleptic and epicormic shoots on mature, field-grown peach trees. Leaf growth measurements were recorded three times per week from the beginning to the end of the growing season and used to calculate the phyllochron on trees from two treatments; one with 100% of the crop left on it (unthinned or fully cropped) and a treatment of trees where the crop was completely removed (non-cropped). The phyllochron fluctuated but generally increased over the season due to a rank effect. The phyllochron was longer on trees with heavy crop loads. Although there were large differences in phyllochrons between treatments in both shoot types, only differences observed in epicormic shoots were statistically significant. Additionally, leaf length and leaf area were also significantly reduced by crop load in both shoot types. These findings indicate that the phyllochron of field-grown peach trees is apparently sensitive to carbohydrate availability in the tree and should be considered when trying to accurately predict the timing of the addition of new phytomers along a shoot.

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 (RUEshoot) in the first spring. A 40% reduction in RUEshoot 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 RUEshoot 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.

Background and Aims Daylength determines flowering dates. However, questions remain regarding flowering dates in the natural environment, such as the synchronous flowering of plants sown simultaneously at highly contrasting latitudes. The daily change in sunrise and sunset times is the cue for the flowering of trees and for the synchronization of moulting in birds at the equator. Sunrise and sunset also synchronize the cell circadian clock, which is involved in the regulation of flowering. The goal of this study was to update the photoperiodism model with knowledge acquired since its conception. Methods A large dataset was gathered, including four 2-year series of monthly sowings of 28 sorghum varieties in Mali and two 1-year series of monthly sowings of eight rice varieties in the Philippines to compare with previously published monthly sowings in Japan and Malaysia, and data from sorghum breeders in France, Nicaragua and Colombia. An additive linear model of the duration in days to panicle initiation (PI) and flowering time using daylength and daily changes in sunrise and sunset times was implemented. Key Results Simultaneous with the phyllochron, the duration to PI of field crops acclimated to the mean temperature at seedling emergence within the usual range of mean cropping temperatures. A unique additive linear model combining daylength and daily changes in sunrise and sunset hours was accurately fitted for any type of response in the duration to PI to the sowing date without any temperature input. Once calibrated on a complete and an incomplete monthly sowing series at two tropical latitudes, the model accurately predicted the duration to PI of the concerned varieties from the equatorial to the temperate zone. Conclusions Including the daily changes in sunrise and sunset times in the updated photoperiodism model largely improved its accuracy at the latitude of each experiment. More research is needed to ascertain its multi-latitudinal accuracy, especially at latitudes close to the equator.

38 Pags.- 13 Figs.- 2 Tabls. The definitive version is available at: https://www.sciencedirect.com/science/journal/11610301, Genetic gains in wheat yield are required to meet future demand. In order to design strategic crosses, it is essential to quantify the genetic variation among elite cultivars on traits responsible for the adaptation and the generation of yield components. We explored the degree of variation within well-adapted commercial cultivars on developmental phases (vegetative, early reproductive and late reproductive), final leaf number and phyllochron, leaf and spikelet plastochron, number of spikelets, florets, and dynamics of floret primordia development. Variation in flowering time among cultivars was minor but they differed in the partitioning of that time into particular phases. Main differences were found for the length of the late reproductive phase, partly linked to those in final leaf number. Variations on number of fertile florets at anthesis were mostly explained by floret survival, due to differential ability of labile florets to maintain normal development between cultivars. These differences were related to the duration of the floret development, but not to the synchrony of development among florets. These findings provide useful information for breeders when selecting genotypes for strategic crosses, as considering floret survival through duration of floret development in one of the parents (for which these processes shall be characterised in the elite germplasm) might increase the likelihood of transgressive segregation towards high-yielding offspring., Funding was provided by ADAPTAWHEAT (a project funded by the European Commission under the 7th Framework Programme for Research and Technological Development) and by project AGL2012- 35300 funded by the Ministry of Economy and Competitiveness of Spain. HO held a FPI scholarship from the Spanish Ministry of Science and Innovation, and PP held a PhD scholarship from the University of Lleida.

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, &ldquo, cores&rdquo, 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.

Miscanthus is a close relative of Saccharum and a potentially valuable genetic resource for improving sugarcane. Differences in flowering time within and between Miscanthus and Saccharum hinders intra- and interspecific hybridizations. A series of greenhouse experiments were conducted over three years to determine how to synchronize flowering time of Saccharum and Miscanthus genotypes. We found that day length was an important factor influencing when Miscanthus and Saccharum flowered. Sugarcane could be induced to flower in a central Illinois greenhouse using supplemental lighting to reduce the rate at which days shortened during the autumn and winter to 1 min d-1, which allowed us to synchronize the flowering of some sugarcane genotypes with Miscanthus genotypes primarily from low latitudes. In a complementary growth chamber experiment, we evaluated 33 Miscanthus genotypes, including 28 M. sinensis, 2 M. floridulus, and 3 M. ×giganteus collected from 20.9° S to 44.9° N for response to three day lengths (10 h, 12.5 h, and 15 h). High latitude-adapted M. sinensis flowered mainly under 15 h days, but unexpectedly, short days resulted in short, stocky plants that did not flower; in some cases, flag leaves developed under short days but heading did not occur. In contrast, for M. sinensis and M. floridulus from low latitudes, shorter day lengths typically resulted in earlier flowering, and for some low latitude genotypes, 15 h days resulted in no flowering. However, the highest ratio of reproductive shoots to total number of culms was typically observed for 12.5 h or 15 h days. Latitude of origin was significantly associated with culm length, and the shorter the days, the stronger the relationship. Nearly all entries achieved maximal culm length under the 15 h treatment, but the nearer to the equator an accession originated, the less of a difference in culm length between the short-day treatments and the 15 h day treatment. Under short days, short culms for high-latitude accessions was achieved by different physiological mechanisms for M. sinensis genetic groups from the mainland in comparison to those from Japan; for mainland accessions, the mechanism was reduced internode length, whereas for Japanese accessions the phyllochron under short days was greater than under long days. Thus, for M. sinensis, short days typically hastened floral induction, consistent with the expectations for a facultative short-day plant. However, for high latitude accessions of M. sinensis, days less than 12.5 h also signaled that plants should prepare for winter by producing many short culms with limited elongation and development; moreover, this response was also epistatic to flowering. Thus, to flower M. sinensis that originates from high latitudes synchronously with sugarcane, the former needs day lengths >12.5 h (perhaps as high as 15 h), whereas that the latter needs day lengths

Development models are tools used to evaluate the development of forest species under current and future climate conditions. However, there are scarce studies on native forest species, despite their ecological and economic potential. This study aims to calibrate and evaluate two development models under field experimental conditions, as well as to identify possible changes in the development of the Anadenanthera peregrina (L.) Speg. and Libidibia ferrea (Mart. ex Tul.) L.P.Queiroz, both forest species native to Brazil, under current and future climate conditions. The Phyllochron (Phyl) and Wang and Engel (WE) development models estimate on a daily basis the cumulative leaf number (CLN), which integrated on time provides the seedling phase duration (SPD). First, both models were parameterized and evaluated under field experimental conditions. For that, data from field experiments conducted during 2017 and 2018 growing seasons and twelve sowing dates in Itajuba, Minas Gerais, Brazil, were used. These two species X sowing dates x years experiments provided a rich data set for parameterizing and evaluating the Phyl and WE development models. Subsequently, the best development model was applied on current (1980–2004) and on two future (2021–2050 and 2071–2099) climate conditions in two emission scenarios (RCP4.5 and RCP8.5). Data from eight Earth System Models from NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) were used. Both development models were able to predict the CLN for both species, with less accuracy in SPD prediction. For A. peregrina the Phyl model was superior to the CLN (RMSE = 2.93 leaves), however, it was not accurate in predicting the SPD (RMSE = 29.1 days). For L. ferrea the WE model was superior mainly in SPD prediction (RMSE = 9.2 days). Climate projections indicate an increase in air temperature (up to 3.9 °C in 2100) and changes in the initial development of the two native forest species. While to change sowing dates is a feasible adaptation measure against the threats of climate change, shading and irrigation may reduce the quality of seedlings. Outlining appropriate, timely and cost effective adaptation measures is critical for the sustainability of the Brazilian nursery sector.

RESUMO O objetivo deste trabalho foi avaliar o filocrono e o requerimento térmico de híbridos de tomateiro italiano nas diferentes fases fenológicas e em diferentes ciclos de cultivo. Os experimentos foram conduzidos na área experimental da Universidade Federal de Santa Maria, campus de Frederico Westphalen-RS, nos anos 2012 e 2013. O delineamento foi em blocos casualizados, em esquema 2x2x5, com dois híbridos de tomateiro, dois ciclos de cultivo e cinco fases fenológicas, em quatro repetições. Foram avaliados os híbridos San Vito e Netuno, com hábito de crescimento indeterminado, no inverno-primavera e no verão-outono. A soma térmica para cada fase fenológica foi calculada pelo acúmulo de temperatura no decorrer das mesmas. O híbrido San Vito apresentou filocrono superior ao Netuno no inverno-primavera, e no verão-outono ambos foram semelhantes. O requerimento térmico total para o cultivo de inverno-primavera foi de 1749,4 e 1717,5 graus dias para os híbridos San Vito e Netuno e de 1534,6 e 1495,2 graus dias no verão-outono, respectivamente. O híbrido Netuno foi mais precoce e apresentou período produtivo mais longo. No ciclo inverno-primavera, o maior requerimento térmico ocorreu na fase de maturação dos frutos, enquanto que no verão-outono ocorreu na fase de crescimento vegetativo. No verão-outono, o ciclo de ambos os híbridos foi menor, com produção mais precoce e concentrada dos frutos. ABSTRACT The objective of this study was to evaluate the phyllochron and the thermal requirement of Italian tomato hybrids in different phenological phases and different cycles of cultivation. The experiments were carried out in the experimental area of the Federal University of Santa Maria campus Frederico Westphalen, Rio Grande do Sul State, Brazil, in the years 2012 and 2013. The experimental design was a randomized block 2x2x5, with two tomato hybrids, two crop cycles and five phenological stages, with four replications. Hybrids San Vito and Neptune were evaluated, with indeterminate growth habit, during winter-spring and summer-autumn. Thermal needs for each phenological phase was calculated by the accumulation of temperature throughout each phase. Hybrid San Vito showed a phyllochron superior to Neptune in the winter-spring, but, both were similar in summer-autumn. The total thermal requirement for the winter-spring crop was 1749.4 and 1717.5 degrees days for San Vito and Neptune hybrids and 1534.6 and 1495.2 degrees days in the summer-autumn, respectively. Neptune hybrid was earlier and presented a longer production period. In the winter-spring cycle, the highest thermal requirement occurred in fruit maturation phase, while in the summer-fall, the highest thermal requirement occurred in the vegetative growth stage. During summer-autumn, the cycle of both hybrids was shorter, with early production and concentrated fruiting period.

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.

Several strawberry growers have cultivated the same plants for two consecutive cycles aiming a greater economic return after seedling transplant. However, the phenological development and the agronomic potential of second-cycle strawberry have to be estimated. This research was installed to estimate the thermal need, leaf appearance rate, phyllochron and yield of strawberry cultivars in two consecutive crop cycles in the region of the Third Planalto Paranaense. Cultivars Camarosa, Camino Real, Albion, Aromas, Monterrey and San Andreas were evaluated in the first and second growing cycles using completely randomized blocks and four replications. Leaf appearance rate was estimated by linear regression coefficient between the number of leaves and the accumulated thermal sum. Phyllochron was estimated by the inverse of regression coefficient. Aromas was the only cultivar with an increased fruit production in the second cycle. On the contrary, there was a considerable reduction of production for ‘Camino Real’, ‘Albion’, ‘Monterrey’ and ‘San Andreas’ in that same cycle. The highest number and mass of marketable fruits of the second and first cycles were observed for ‘Camarosa’ and ‘Camino Real’, respectively. In the second crop cycle, strawberry cultivars required a lower thermal sum to begin flowering and fruit harvest. The plants presented a higher leaf appearance rate and low phyllochron values. RESUMO Em busca de maior retorno econômico após o transplantio das mudas, muitos produtores de morango têm feito o cultivo por dois ciclos consecutivos. No entanto, há necessidade de estimar o desenvolvimento fenológico e avaliar o potencial agronômico do morangueiro nesse sistema. O objetivo deste trabalho foi comparar a necessidade térmica, a taxa de aparecimento foliar, o filocrono e a produtividade de cultivares de morangueiro no segundo ciclo de cultivo, em comparação ao primeiro, na região do Terceiro Planalto Paranaense. Avaliaram-se as cultivares Camarosa, Camino Real, Albion, Aromas, Monterrey e San Andreas, utilizando o delineamento experimental de blocos ao acaso e com quatro repetições. A taxa de aparecimento foliar foi estimada a partir do coeficiente angular da regressão linear entre o número de folhas e a soma térmica acumulada, enquanto o filocrono foi estimado pelo inverso do coeficiente angular da regressão. Observou-se que Aromas foi a única cultivar que aumentou a produção de frutos no segundo ciclo. Ao contrário, nesse mesmo ciclo houve considerável redução da produção para ‘Camino Real’, ‘Albion’, ‘Monterrey’ e ‘San Andreas’. Destacaram-se com maior número e massa de frutos comerciais do segundo e primeiro ciclo, ‘Camarosa’ e ‘Camino Real’, respectivamente. No segundo ciclo de cultivo, as cultivares de morangueiro necessitaram menor soma térmica acumulada para iniciar o florescimento e colheita dos frutos e, apresentaram maior taxa de aparecimento foliar e menores valores de filocrono.

Highlight An efficient workflow based on photos to monitor early growth and development of isolated wheat plants dynamically is described, Early vigour is an important physiological trait to improve establishment, water-use efficiency, and grain yield for wheat. Phenotyping large numbers of lines is challenging due to the fast growth and development of wheat seedlings. Here we developed a new photo-based workflow to monitor dynamically the growth and development of the wheat canopy of two wheat lines with a contrasting early vigour trait. Multiview images were taken using a ‘vegetation stress’ camera at 2 d intervals from emergence to the sixth leaf stage. Point clouds were extracted using the Multi-View Stereo and Structure From Motion (MVS-SFM) algorithm, and segmented into individual organs using the Octree method, with leaf midribs fitted using local polynomial function. Finally, phenotypic parameters were calculated from the reconstructed point cloud including: tiller and leaf number, plant height, Haun index, phyllochron, leaf length, angle, and leaf elongation rate. There was good agreement between the observed and estimated leaf length (RMSE=8.6mm, R 2=0.98, n=322) across both lines. Significant contrasts of phenotyping parameters were observed between the two lines and were consistent with manual observations. The early vigour line had fewer tillers (2.4±0.6) and larger leaves (308.0±38.4mm and 17.1±2.7mm for leaf length and width, respectively). While the phyllochron of both lines was quite similar, the non-vigorous line had a greater Haun index (more leaves on the main stem) on any date, as the vigorous line had slower development of its first two leaves. The workflow presented in this study provides an efficient method to phenotype individual plants using a low-cost camera (an RGB camera is also suitable) and could be applied in phenotyping for applications in both simulation modelling and breeding. The rapidity and accuracy of this novel method can characterize the results of specific selection criteria (e.g. width of leaf three, number of tillers, rate of leaf appearance) that have been or can now be utilized to breed for early leaf growth and tillering in wheat.

Fodder beet is a highly productive forage crop of expanding use in livestock production systems in temperate regions, notably in Europe and New Zealand. The main determinant of fodder beet productivity is the amount of light intercepted by the crop canopy, which is regulated by temperature and the availability of water and nitrogen (N) for plant development and growth. The quantitative understanding of canopy formation processes under constraining growth conditions is an essential step for the development of biophysical simulation models of new crops for research and predictive purposes. In this study, we provided the first estimates of key canopy formation parameters in fodder beet both under optimum and water- and N-limited supply, in two field experiments in Lincoln, Canterbury, New Zealand. Specifically, the base temperature for leaf appearance in fodder beet was estimated as 0 °C. The range of the critical LAI (c. 90–95% of light interception) was 3–4 m 2 /m 2 . The phyllochron was 48–53 °Cd/leaf in unstressed crops and 60 °Cd/leaf in water stressed crops, with no effect of N supply. Leaf senescence rates varied widely (from 42 to 260 °Cd/leaf) depending on water availability and canopy cover. Leaf expansion, appearance and senescence rates fully recovered following a period of water stress to values similar to those observed in unstressed crops in response to late season rainfall events. Leaf area expansion rates (LAER) ranged from 0.0012 to 0.0034 m 2 /m 2 /°Cd and was reduced both by limited water and N supply. Leaf area senescence rates (LASR) ranged from 0.0005 to 0.0019 m 2 /m 2 /°Cd, with low values recorded during drought periods when crop growth was negligible. Canopy architecture, characterised by the extinction coefficient ( k ), was less sensitive to water stress than canopy expansion or senescence with a conservative value of 0.74. This first quantitative description of fodder beet canopy forming processes can assist the development of predictive approaches, such as biophysical simulation models, for application in research, extension and teaching.

The extraction of desirable heritable traits for crop improvement from high-throughput phenotyping (HTP) observations remains challenging. We developed a modeling workflow named “Digital Plant Phenotyping Platform” (D3P), to access crop architectural traits from HTP observations. D3P couples the Architectural model of DEvelopment based on L-systems (ADEL) wheat (Triticum aestivum) model (ADEL-Wheat), which describes the time course of the three-dimensional architecture of wheat crops, with simulators of images acquired with HTP sensors. We demonstrated that a sequential assimilation of the green fraction derived from Red–Green–Blue images of the crop into D3P provides accurate estimates of five key parameters (phyllochron, lamina length of the first leaf, rate of elongation of leaf lamina, number of green leaves at the start of leaf senescence, and minimum number of green leaves) of the ADEL-Wheat model that drive the time course of green area index and the number of axes with more than three leaves at the end of the tillering period. However, leaf and tiller orientation and inclination characteristics were poorly estimated. D3P was also used to optimize the observational configuration. The results, obtained from in silico experiments conducted on wheat crops at several vegetative stages, showed that the accessible traits could be estimated accurately with observations made at 0° and 60° zenith view inclination with a temporal frequency of 100 °Cd (degree day). This illustrates the potential of the proposed holistic approach that integrates all the available information into a consistent system for interpretation. The potential benefits and limitations of the approach are further discussed.

International audience; 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.

The objective of this study was to determine the base temperature of escarole and to apply in the phenological analysis of crop during four growing periods. The study was carried out with escarole (Chicorium endivia) ‘Escarola Lisa’ cultivar, at the Federal University of Santa Maria, campus Frederico Westphalen-RS. The experiment was performed in a randomized block design with four sowing periods (P1: 2/15/2015; P2: 04/29/2015, P3: 07/22/2015, P4: 10/16/2015) and 10 replicates, each replicate being one plant. The evaluations consisted of counting the number of leaves, performed three times a week after transplanting date until the harvesting point. To determine the base temperature, the following methods were used: standard deviation in degree-days (SDgd), standard deviation in days (SDd), coefficient of variation in degree-days (CVgd), coefficient of variation in days (CVd), regression coefficient (RC) and X-intercept. The base temperature for emission of two successive leaves in the escarole is 4.7°C, obtained by values of 4.0 and 5.5°C, observed in the SDgd and RC methods. For two leaves emission, the temperature between 16.6 and 27.8°C day leaf-1 is necessary. RESUMO O objetivo deste trabalho foi determinar a temperatura base da chicória e aplicá-la na análise fenológica da cultura, durante quatro períodos de cultivo. O trabalho foi realizado com a cultura da chicória (Chicorium endivia) cultivar Escarola Lisa, na Universidade Federal de Santa Maria, campus Frederico Westphalen-RS. O experimento foi conduzido em delineamento de blocos ao acaso com quatro períodos de cultivo (P1: 15/2/2015; P2: 29/04/2015, P3: 22/07/2015, P4: 16/10/2015) em 10 repetições, com uma planta por repetição. As avaliações consistiram da contagem do número de folhas, realizada três vezes por semana após transplante até o ponto de colheita. Para determinação de temperatura base utilizaram-se os métodos desvio padrão em graus dias (DPgd), desvio padrão em dias (DPd), coeficiente da variação em graus dias (CVgd), coeficiente de variação em dias (CVd), coeficiente de regressão (CR), X-intercepto. Desta forma, a temperatura base para emissão de duas folhas sucessivas na escarola é de 4,7°C, obtida através dos valores de 4,0 e 5,5°C, observados nos métodos DPgd e CR. Para a emissão de duas folhas é necessário entre 16,6 e 27,8°C dia folha-1.

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 [CO(2)] 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 CO(2) 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 [CO(2)] 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.

To quantify the influence of autumn (fall) dormancy (FD) on DM production and phenological development during the seedling phase, three lucerne genotypes with contrasting ratings were grown at Lincoln University, New Zealand. A dormant (FD2), a semi-dormant (FD5), and a winter-active (FD10) genotype were inoculated and sown at a rate of 290 plants/m2 on 8 October 2014. By the end of the seedling phase (15 January 2015) the FD10 genotype had produced 20% higher shoot yield and 17% higher root yield than the other two genotypes. The percentage of total biomass partitioned to roots (Proot) was 50% for all genotypes. Total plant biomass (root + shoot yields) was 6.55 t DM/ha for FD10 compared with 5.57 t DM/ha for FD 2 and FD5. Plant height at the open-flower stage was 39.5 cm for FD10 compared with 34.5 cm for FD5 and 33.5 cm for FD2. Maximum leaf area index was similar amongst genotypes at 2.5. However, individual leaf area was 142, 119 and 111 cm2/stem for FD10, FD5 and FD2, respectively. The phyllochron was 52oCd per primary leaf (base temperature of 1oC) and consistent amongst genotypes. The number of primary leaves and branches were also conservative at 17 and 14/shoot, respectively. Therefore, differences in shoot yield among these lucerne genotypes during the seedling stage were mainly due to differences in plant height and individual leaf area expansion per plant. This led to greater light interception and therefore higher total biomass accumulation for FD10 than for the other two genotypes. Keywords: alfalfa, autumn, Medicago sativa L., phyllochron

Leaf appearance rate and time to canopy expansion of four annual clover species (arrowleaf, balansa, gland and Persian) were quantified in field and controlled environment studies. Crops sown in autumn, which experienced shortening daylengths at emergence, had a slower rate of leaf production and consequently took a longer time to initiate branching, than spring-sown crops. When autumn-sown ‘Bolta’ balansa clover emerged on the shortest day in winter (21 June), the rate of leaf appearance was lengthened by 4 °C d/leaf/h. When the same species emerged after the shortest day, into an increasing photoperiod, the phyllochron was shortened by 5 °C d/leaf/h. This influence of photoperiod on the phyllochron consequently altered the time to axillary leaf production (branching). Throughout all sowing dates, phyllochron was the fastest for ‘Prima’ gland (33–91 °C d/leaf) and slowest for ‘Cefalu’ arrowleaf (53–116 °C d/leaf) clovers. ‘Bolta’ balansa was 44–82 °C d/leaf and ‘Mihi’ Persian 61–93 °C d/leaf. The response of phyllochron to photoperiod suggests these annual clovers should be sown in late summer or early autumn to initiate axillary leaf production as soon as possible to ensure maximize dry matter for early spring.

The aim of this study was to analyse (i) the crop attributes that determine flowering time (i.e. final leaf number, FLN; and phyllochron, Phy), (ii) the dynamics of tiller appearance and (iii) the synchrony between leaf and tiller appearance in wheat and barley plants exposed to waterlogging. Two experiments were carried out in pots, in which wheat and barley cultivars were exposed to five waterlogging treatments, during different periods throughout the crop cycle, from emergence to maturity. The appearance of leaves and tillers on the main stem was measured twice a week in labelled plants. Waterlogging from emergence to flag leaf appearance significantly delayed time to flowering. The delay was greater when waterlogging occurred at the beginning of tillering, lengthening the period from emergence to flowering 24 % (13–15 days) in barley and 10–15 % (6–10 days) in wheat, as compared to control. Phy was the main attribute explaining the delay in flowering, as FLN was not altered. Waterlogging during the early stages of development reduced tiller appearance rate (TAR) in both species, but this effect was partially counterbalanced by a lengthening of the tillering phase, so the effect on final tiller number at maturity was limited. In conclusion, the exposure of wheat and barley to waterlogging during early stages of development delayed time to flowering and reduce TAR in both species. Waterlogging during more advanced crop stages produced slight effects on tillering dynamics, which would indicate that waterlogging affected structure generation more than mortality.

Rapid leaf growth during the recovery period after a dry spell is essential for the adaptation of rice ( Oryza sativa L.) to drought–prone environments. However, how rice plants resume growth when the drought stress ends is not well understood. The objective of this study was to determine the traits and mechanisms associated with the above-ground morphological response to rewatering after early-season drought, by comparing three rice lines with contrastive plant architectures. In the field, we measured the above-ground architecture, carbohydrate partitioning, and consumption of non-structural carbohydrates by IR64 ( indica rice), a New Plant Type line (tropical japonica rice) and an IR64 introgression line (IL) with large leaves and reduced tillering under fully irrigated and drought + rewatered conditions. In an ancillary pot experiment, we monitored changes in tiller number and leaf growth under fully irrigated, droughted and drought + rewatered conditions. There were genotypic differences in recovery growth patterns upon rewatering after drought: the New Plant Type lines prioritized individual tiller growth, while IR64 and the IR64 IL prioritized the production of new tillers and concomitantly consumed much carbohydrate. The increase in tiller number during the recovery period was lower in the IR64 IL than in IR64 owing to the longer phyllochron and larger amount of assimilate required to produce new tillers in the IL. Rice development during the recovery period depends on the plant type (constitutive tiller number to size ratio) and tillering response to soil moisture regime, which would be mediated mainly by phyllochron and tiller production per assimilate. Rapid increase in tiller number upon rewatering in IR64 was associated with the low amount of assimilate required to produce new tillers rather than with the short phyllochron.

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.

Mixed cropping is practised widely in developing countries and is gaining increasing interest for sustainable agriculture in developed countries. Plants in intercrops grow differently from plants in single crops, due to interspecific plant interactions, but adaptive plant morphological responses to competition in mixed stands have not been studied in detail. Here the maize (Zea mays) response to mixed cultivation with wheat (Triticum aestivum) is described. Evidence is provided that early responses of maize to the modified light environment in mixed stands propagate throughout maize development, resulting in different phenotypes compared with pure stands. Photosynthetically active radiation (PAR), red:far-red ratio (R:FR), leaf development, and final organ sizes of maize grown in three cultivation systems were compared: pure maize, an intercrop with a small distance (25 cm) between maize and wheat plants, and an intercop with a large distance (44 cm) between the maize and the wheat. Compared with maize in pure stands, maize in the mixed stands had lower leaf and collar appearance rates, increased blade and sheath lengths at low ranks and smaller sizes at high ranks, increased blade elongation duration, and decreased R:FR and PAR at the plant base during early development. Effects were strongest in the treatment with a short distance between wheat and maize strips. The data suggest a feedback between leaf initiation and leaf emergence at the plant level and coordination between blade and sheath growth at the phytomer level. A conceptual model, based on coordination rules, is proposed to explain the development of the maize plant in pure and mixed stands.

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitières; In crops, optimizing target traits in breeding programs can be fostered by selecting appropriate combinations of architectural traits which determine light interception and carbon acquisition. In apple tree, architectural traits were observed to be under genetic control. However, architectural traits also result from many organogenetic and morphological processes interacting with the environment. The present study aimed at combining a FSPM built for apple tree, MAppleT, with genetic determinisms of architectural traits, previously described in a bi-parental population. We focused on parameters related to organogenesis (phyllochron and immediate branching) and morphogenesis processes (internode length and leaf area) during the first year of tree growth. Two independent datasets collected in 2004 and 2007 on 116 genotypes, issued from a ‘Starkrimson’ × ‘Granny Smith’ cross, were used. The phyllochron was estimated as a function of thermal time and sylleptic branching was modeled subsequently depending on phyllochron. From a genetic map built with SNPs, marker effects were estimated on four MAppleT parameters with rrBLUP, using 2007 data. These effects were then considered in MAppleT to simulate tree development in the two climatic conditions. The genome wide prediction model gave consistent estimations of parameter values with correlation coefficients between observed values and estimated values from SNP markers ranging from 0.79 to 0.96. However, the accuracy of the prediction model following cross validation schemas was lower. Three integrative traits (the number of leaves, trunk length, and number of sylleptic laterals) were considered for validating MAppleT simulations. In 2007 climatic conditions, simulated values were close to observations, highlighting the correct simulation of genetic variability. However, in 2004 conditions which were not used for model calibration, the simulations differed from observations. This study demonstrates the possibility of integrating genome-based information in a FSPM for a perennial fruit tree. It also showed that further improvements are required for improving the prediction ability. Especially temperature effect should be extended and other factors taken into account for modeling GxE interactions. Improvements could also be expected by considering larger populations and by testing other genome wide prediction models. Despite these limitations, this study opens new possibilities for supporting plant breeding by in silico evaluations of the impact of genotypic polymorphisms on plant integrative phenotypes.

Field experiments were conducted in the Ebro Delta area (Spain), from 2007 to 2009 with two rice varieties: Gleva and Tebre. The experimental treatments included a series of seed rates, two different water management systems and two different nitrogen fertilization times. The number of leaves on the main stems and their emergence time were periodically tagged. The results indicated that the final leaf number on the main stems in the two rice varieties was quite stable over a three-year period despite of the differences in their respective growth cycles. Interaction between nitrogen fertilization and water management influenced the final leaf number on the main stems. Plant density also had a significant influence on the rate of leaf appearance by extending the phyllochron and postponing the onset of intraspecific competition after the emergence of the 7th leaf on the main stems. Final leaf number on the main stems was negatively related to plant density. A relationship between leaf appearance and thermal time was established with a strong nonlinear function. In direct-seeded rice, the length of the phyllochron increases exponentially in line with the advance of plant development. A general model, derived from 2-year experimental data, was developed and satisfactorily validated; it had a root mean square error of 0.3 leaf. An exponential model can be used to predict leaf emergence in direct-seeded rice.

Drought can result in severely decreased leaf area development, which impacts plant growth and yield. However, rarely is leaf emergence or leaf expansion separated to resolve the relative sensitivity to water-deficit of these two processes. Experiments were undertaken to impose drought over approximately 2 weeks for eight cowpea (Vigna unguiculata) genotypes grown in pots under controlled environmental conditions. Daily measures of phyllochron index (PI, leaf emergence) and leaf area increase (leaf expansion) were obtained. Each of these measures was referenced against volumetric soil water content, i.e. fraction transpirable soil water. Although there was no clear difference between leaf emergence and leaf expansion in sensitivity to drying soil, both processes were more sensitive to soil drying than plant transpiration rate. Genotypic differences in the soil water content at the initiation of the decline in PI were identified. However, no consistent difference in sensitivity to water-deficit in leaf expansion was found. The difference in leaf emergence among genotypes in sensitivity to soil drying can now be exploited to provide guidance for plant improvement and crop yield increase.

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 aimed to elucidate seasonal dynamics of ryegrass root systems in field swards. Established field swards of perennial ryegrass with white clover removed by herbicide and fertilised with nitrogen (N) to replace clover N fixation were subjected to lax and hard grazing management and root biomass deposition monitored using a root ingrowth core technique over a 13 month period. A previously published phytomer-based model of plant morphology that assumes continuous turnover of the root system was used to estimate mean individual root weight (mg) not previously available for field swards. The predicted root weights compared credibly with root data from hydroponic culture and the model output explained much of the seasonal variation in the field data. In particular, root deposition showed a seasonality consistent with influence of an architectural signal (AS) determined by plant morphology. This AS arises because it is theoretically expected that with rising temperatures and decreasing phyllochron in early summer, more than one leaf on average would feed each root bearing node. Conversely, in autumn the reverse would apply and root deposition is expected to be suppressed. The phytomer-based model was also able to explain deeper root penetration in summer dry conditions, as seen in the field data. A prediction of the model is that even though total root deposition is reduced by less than 10% under hard grazing, individual root weight is reduced proportionately more because the available substrate is being shared between a higher population of tillers. Two features of the field data not explained by the phytomer based model, and therefore suggestive of hormonal signaling, were peaks of root production after summer drought and in late winter that preceded associated herbage mass rises by about one month. In summary, this research supports a view that the root system of ryegrass is turning over on a continuous basis, like the leaves above ground. The phytomer based model was able to explain much of the seasonal variation in root deposition in field swards, and also predicts a shift of root deposition activity, deeper in summer and shallower in winter.

In grasses, tillering is at least in part controlled by auxins and cytokinins. The participation of other hormones is less clear, but there is evidence that gibberellins may also play a role, as suggested by earlier tillering in plants treated with gibberellin synthesis inhibitors. This study evaluates the effect of paclobutrazol (PBZ), a gibberellin synthesis inhibitor, on tiller development in wheat. Experiments were conducted under controlled conditions, and PBZ was supplied to the root medium. PBZ caused a significant advancement of the onset of tillering compared with the controls. However, no effects on site filling were observed. Earlier tillering in PBZ-treated plants was associated with a promotive effect on the rate of leaf appearance. PBZ-treated plants had lower height, higher chlorophyll content, a trend to a higher quantum yield of photosystem II, increased dry matter content and a higher concentration of soluble sugars. The results suggest that an increased carbohydrate status in P...

Successful control of wild oat in cereal crops requires an accurate prediction of the developmental stages of wild oat plants that emerged during the growing season. The main objective of this research was to evaluate wild oat growth and to predict the phyllochron of wild oat plants that emerge at various times in the Red River Valley region of Minnesota and North Dakota. Field experiments were conducted in 2002 and 2003 in Crookston, MN, and Fargo, ND. Four emergence cohorts were established in 4 successive wk. Research plots were arranged in randomized complete blocks with six replications. From the naturally emerged wild oat population, 10 randomly selected plants per plot were evaluated for plant height, leaves on main stem, tillers per plant, total leaves per plant, days to flag leaf emergence and to heading, biomass per plant, and seeds per plant. Haun's numerical cereal development scale was regressed on days after emergence (DAE), day length (DL), growing degree days (GDD), or photothermal units (PTU). Wild oats that emerged first required more time for flag leaf emergence and heading, were taller, and had more biomass, leaves, tillers, and seed production than wild oat plants that emerged later. Wild oat phyllochron intervals were 5.3 d, 94 GDD, or 1,468 PTU, regardless of emergence timing. These data suggest that wild oat phyllochron is primarily driven by air temperature and is relatively stable during the extended emergence period. Later-emerging wild oat plants, although not as competitive as earlier emerging ones, still have the potential to contribute to the seed bank if left uncontrolled.

Early vigour is an important objective in rice breeding. A previous study reported strong positive effects of development rate (DR, 1/phyllochron) on early growth vigour in two rice panels. This study provided a model-based analysis of DR effects on rice early vigour and underlying source-sink processes during exponential growth, using Ecomeristem model. Relevant model parameters were fitted to panel observations, and their effect on early vigour was quantified. A sensitivity analysis was performed to quantify the impact of model parameters on simulation outputs. The simulated behaviour of a population of virtual genotypes defined by the combination of model parameter values was compared with that of diversity panel. Finally, a simulation experiment was conducted to analyse source-sink adjustments constituting early vigour across a range of DR. Parameters governing structural development, particularly DR, had greater impact on vigour than parameters for resource acquisition. High DR was associated with rapid dry weight accumulation and low transitory carbohydrate reserves in both real and virtual populations. Genotypic DR is thus a major driver of early vigour in rice under stress-free conditions. To evaluate traits contributing to vigour, the capacity of crop models to simulate interactions between structural development and resource acquisition must be improved. (Resume d'auteur)

Achieving early vigour, that is, rapid dry matter accumulation, is a priority in rice crop improvement, but this trait is complex and not well understood genetically and physiologically. This study tested the hypothesis that the development rate (DR) contributes to early vigour. Two diversity panels were phenotyped during vegetative stage for traits constituting early vigour (shoot dry weight, SDW; relative growth rate, RGR) or contributing to early vigour (tillering, leaf size, DR). The first panel comprised 169 genotypes from all major genetic groups of Oryza sativa and was phenotyped under irrigated upland conditions in the field (Philippines, Exp1). The second panel with 190 genotypes representing the diversity of the tropical japonica group was phenotyped in pots in a greenhouse (Montpellier, France, Exp2). Results from field and pot experiment pointed out that DR, tillering and leaf size were positively correlated with RGR and SDW, although the contribution of leaf size was small. DR was positively correlated with tillering but both were negatively correlated with leaf size. DR vs. RGR correlation was conserved in subsets of genotypes with similar leaf size and tillering, suggesting an effect of DR on RGR independent of the other traits. DR is a promising, still underexploited trait contributing to rice early vigour, requiring further genetic and physiological characterization.

This study compared physiological responses of fully irrigated seedling and regrowth lucerne crops ( Medicago sativa L.) grown under similar environmental field conditions. Measurements occurred for 2–4 years after sowing on 24 October, 15 November, 05 December and 27 December 2000 at Lincoln, Canterbury, New Zealand. Irrespective of the date of sowing, on average lucerne accumulated less shoot dry matter (DM) in the seedling year (11 ± 0.44 t ha −1 ) than during the regrowth year (18 ± 0.76 t ha −1 ). Slower shoot-growth rates in seedlings were explained by less intercepted light and reduced efficiency in conversion of light to biomass. Specifically, seedlings had a longer phyllochron (47 ± 2.3 °Cd leaf −1 ) and slower leaf area expansion rate (0.009 m 2 m −2 °Cd −1 ) than regrowth crops (35 ± 1.8 °Cd leaf −1 and 0.016 m −2 m −2 °Cd, respectively). There were no differences in canopy architecture with a common extinction coefficient of 0.93. The radiation use efficiency (RUE) for shoot production (RUE shoot ) was 1.2 ± 0.16 g DM MJ −1 of intercepted photosynthetically active radiation (PAR i ) in seedlings and 1.9 ± 0.24 g DM MJ −1 PAR i in regrowth crops. Reproductive development was slower in seedling than regrowth crops due to an apparent juvenile period ranging from 240 to 530 °Cd in seedlings. For both seedling and regrowth phases, the thermal time accumulation to reach 50% buds visible (Tt 0-bv ) and 50% open flowers (Tt 0-fl ) increased as photoperiod shortened in autumn. The minimum Tt 0-bv , or the thermal-time duration of the basic vegetative period (Tt BVP ), was estimated at 270 ± 48 °Cd at photoperiods >14 h for regrowth crops. The theoretical threshold below which reproductive development is projected to cease, or the base photoperiod (Pp base ), was estimated at a common 6.9 h for seedling and regrowth crops. The transition from buds visible to open flowers (Tt bv-fl ) was mainly controlled by air temperature and ranged from 161 °Cd for seedlings to 274 °Cd for regrowth crops. These results can be used as guidelines to develop differential management strategies for seedling and regrowth crops and improve the parameterization of lucerne simulation models.

2011). Phyllochron and leaf lifespan are morphogenic pro-cesses that control growth and development of plants by determining leaf area index and thus light interception by the sward (Lemaire and Chapman 1996). Both char-acteristics can be used as tools for pasture management and are influenced by management practices, like nitro-gen fertilization. However, few studies have examined these characteristics for forages under a tree canopy (Paciullo et al. 2008), particularly when using light interception (LI) as a criterion for cutting frequency. Under full sun, rotational stocking using 95% canopy LI has been recommended for using C4 species to their fullest potential and to optimize ruminant weight gains on pastures (da Silva and Carvalho 2005). The aim of our work was to determine the effects of shading (5-year-old plantation of

Understanding plant development and architecture has been aided by the phytomer concept. The phytomer, usually considered a vegetative unit of a leaf, node, internode, axillary bud, and occasionally nodal roots, has been extended to the inflorescence with units repeated within and among shoots. For many reasons including insufficient knowledge of phytomer dynamics or specific modelling objectives, crop models may not fully incorporate phytomer concepts. For instance, commonly, some phytomers are aggregated into a single component such as an inflorescence component. Continuing development and maturing of object-oriented (OO) design provides opportunities for better representing phytomer concepts in crop models and integrating approaches using varying scales of resolution. Use of the structural Composite Design Pattern (CDP) in an OO plant design facilitates combining scales with a mixture of single and aggregated phytomers for different components. This paper uses winter wheat (Triticum aestivum L.) to (1) illustrate building the entire plant canopy by the appearance, growth, and death of phytomer units, (2) translate this botanical abstraction into an OO design using the CDP, (3) use the CDP to facilitate a mixture of scales, and (4) present results of a proof-of-concept prototype, CANON, named because the interplay of repeating phytomers is analogous to the repeating melodies of a canon musical composition. CANON implements the phytomer concept of an entire canopy (both vegetative and reproductive phytomers) into an OO design using the CDP. This pattern facilitated the combination of simulation scales from individual reproductive phytomers to an aggregated inflorescence. Quantification of phytomer concepts for winter wheat was primarily derived from the SHOOTGRO model, with the addition of a simple aggregated inflorescence sub-model derived from the APSIM model. The CANON prototype was able to simulate the appearance, growth, and senescence of phytomers on individual shoots of the plant comprising the plant canopy. Importantly, CANON was able to incorporate legacy code with a lower scale of resolution than the phytomer. CANON demonstrates an OO design to simulate plant canopy development and growth from the sub-phytomer to whole-plant level, allowing flexibility in meeting different model objectives and available knowledge of processes.

The current article presents the investigations into the effect of the laurina mutation on the functioning and size of the shoot apical meristem (SAM) in Coffea arabica. This monolocus and Mendelian mutation is known to have pleiotropic effects on tree shape and dwarfism. A comparison between the wild type C. arabica var. Bourbon and its natural dwarf mutant C. arabica var. laurina, also called Bourbon pointu, was carried out leading to three main results: (1) the effects appeared immediately after the emergence of the buttress but did not affect the dome-shaped SAM (size and shape); (2) the effects were located at the peripheral zone and maintained subsequently within the leaf primordia; (3) the effects consisted of reduction in both the size of primordia and the height of incipient internode, consequently resulting in dwarfism of mature leaves and internodes. By contrast, the laurina mutation had no effect on the relationship between the phyllochron and the plastochron, the decussate and opposite phyllotaxis, and the relative timing of SAM functioning within the plastochron.

† Background and Aims Improving the competitive ability of crops is a sustainable method of weed management. This paper shows how a virtual plant model of competition between chickpea (Cicer arietinum) and sowthistle (Sonchus oleraceus) can be used as a framework for discovering and/or developing more competitive chickpea cultivars. † Methods The virtual plant models were developed using the L-systems formalism, parameterized according to measurements taken on plants at intervals during their development. A quasi-Monte Carlo light-environment model was used to model the effect of chickpea canopy on the development of sowthistle. The chickpea– light environment– sowthistle model (CLES model) captured the hypothesis that the architecture of chickpea plants modifies the light environment inside the canopy and determines sowthistle growth and development pattern. The resulting CLES model was parameterized for different chickpea cultivars (viz. ‘Macarena’, ‘Bumper’, ‘Jimbour’ and ‘99071-1001’) to compare their competitive ability with sowthistle. To validate the CLES model, an experiment was conducted using the same four chickpea cultivars as different treatments with a sowthistle growing under their canopy. † Results and Conclusions The growth of sowthistle, both in silico and in glasshouse experiments, was reduced most by ‘99071-1001’, a cultivar with a short phyllochron. The second rank of competitive ability belonged to ‘Macarena’ and ‘Bumper’, while ‘Jimbour’ was the least competitive cultivar. The architecture of virtual chickpea plants modified the light inside the canopy, which influenced the growth and development of the sowthistle plants in response to different cultivars. This is the first time that a virtual plant model of a crop – weed interaction has been developed. This virtual plant model can serve as a platform for a broad range of applications in the study of chickpea– weed interactions and their environment.

The frequency of defoliation is the major management tool that modulates shoot yield and the accumulation of C and N root reserves in lucerne crops. A fully irrigated, 2-year-old lucerne (Medicago sativa L.) crop was grown at Lincoln University (43°38′S and 172°28′E) and subjected to four defoliation treatments. These involved the combination of two grazing frequencies (28 or 42 days) applied before and/or after mid-summer. Annual shoot dry matter (DM) yield ranged from 12 to 23 t/ha. These differences were largely explained by the amount of intercepted photosynthetically active radiation (PARi) using a conservative conversion efficiency of 1.6 g DM/MJ PARi. Part of the reduced PARi in the frequently defoliated treatments was caused by the shorter regrowth period that impeded crop canopy closure to the critical leaf area index (LAIcrit) of 3.6. Canopy architecture was unaffected by treatments and a single extinction coefficient for diffuse PARi (kd) of 0.81 was found for ‘Grasslands Kaituna’ lucerne. The pool of endogenous nitrogen (N) in taproots was reduced by frequent defoliations. This explained differences in leaf area expansion rate (LAER), which decreased from 0.016 m2/(m2 °C day) at 60 kg N/ha to 0.011 m2/(m2 °C day) at 20 kg N/ha. The pool of soluble sugars was also positively associated with LAER but the concentrations of carbohydrates and N reserves and the pool of taproot starch were poorly related to LAER. The slower LAER in the frequently defoliated treatments was mostly caused by the smaller area of primary and axillary leaves, particularly above the 6th node position on the main-stem. Developmental processes were less affected by defoliation frequency. For example, the phyllochron was similar in all treatments at 34 °C day (base temperature of 5 °C) per primary leaf during spring/summer but increased in autumn and ranged between 44 and 60 °C day. Branching and senescence started after the appearance of the 4th main-stem node, and both were unaffected by defoliation frequency. These results suggest that the expansion of individual leaves, both primary and axillary, was the most plastic component of canopy formation, particularly after the appearance of the 6th primary leaf. Future mechanistic modelling of lucerne crops may incorporate the management or environmental responses of LAER that control PARi and impact on shoot DM yields.

Cereal producers are under pressure to increase yields and maintain profitability against a background of environmental constraints and high fertiliser costs. The production of high yields requires high inputs of N, and excessive N can lead to pollution of watercourses. This provides an incentive for the maximisation of nitrogen use efficiency (NUE), defined as grain yield per unit available soil N from all sources. Routes to the improvement of NUE may be through selection of an appropriate environment for the crop, better management or crop genetic improvement. However, the relative importance of these choices is poorly understood. Here we have used a modelling approach to quantify the effects of these factors on NUE. We performed an analysis using the Sirius wheat simulation model for a range of N treatments at two contrasting European sites: Rothamsted. UK and Seville. Spain. Several simple crop traits were selected for sensitivity analysis of NUE. These included traits controlling wheat development, determining sizes of N storage pools in the plant and traits responsible for uptake-efficiency of roots for water and N. We used Sirius because it is based on simple, mechanistic descriptions of wheat phenology and nitrogen uptake and redistribution, which makes it possible to link model cultivar parameters with simple physiological traits. Our analysis showed that weather and N management are the source of large variations in NUE. At Rothamsted, where water was not a limiting factor, N treatments produce more variation in NUE (similar to 51 %) than weather (similar to 32%). At Seville, where water is limited, weather was responsible for larger variation in NUE (for a shallow soil and low N treatment up to similar to 100%) compared with similar to 40% for N treatments. Two traits (leaf [N] and phyllochron) out of six showed potential for improvement of NUE. A decrease in leaf [N] increased NUE by 10-15%, when N was limiting, but for high N supply the effect on NUE was negligible. Increasing phyllochron to delay flowering produced up to 15% increase in NUE at Rothamsted, but no increase at Seville. Our analysis demonstrated that a crop simulation model is a powerful tool for deconvoluting complex traits in wheat. This may facilitate genetic and subsequent genonucs research by focusing experiments only on those wheat traits that are identified by the modelling study as the most promising.

Base temperature (Tb) for leaf appearance and the thermal time interval between appearance of successive leaves (phyllochron) were determined for six common weed species from a series of growth chamber experiments. Mean leaf appearance Tbvalues for giant ragweed, velvetleaf, redroot pigweed, large crabgrass, woolly cupgrass, and wild-proso millet were 1.3, 8.0, 8.5, 4.5, 2.2, and 5.1 C, respectively, and mean phyllochron values were 37.2, 34.4, 17.3, 42.2, 65.2, and 34.2 growing degree-days per leaf, respectively. Phyllochron values increased slightly with mean temperature for each weed species. To our knowledge, these are the first reported leaf appearance Tband phyllochron values for giant ragweed, woolly cupgrass, and wild-proso millet. The results confirm leaf appearance Tband phyllochron values reported previously for velvetleaf and redroot pigweed. However, large crabgrass leaf appearance Tband phyllochron values in our study varied somewhat from those reported previously. The results provide information needed for parameterization of plant growth models that predict leaf development based on thermal time.

RESUMO O objetivo do trabalho foi estimar a soma térmica e o filocrono de quatro cultivares e duas ‘seleções’ de morangueiro para o Planalto Sul- Catarinense. O experimento foi conduzido no Centro de Ciências Agroveterinárias, na Universidade do Estado de Santa Catarina. Foram utilizadas duas seleções de morangueiro em avançada fase de estudos, denominadas ‘SEL1’ e ‘SEL2’, utilizando mudas provenientes de um programa público de melhoramento genético da Itália e quatro cultivares: Camino Real e Camarosa, provenientes do Chile, e San Andreas eAlbion, provenientes da Argentina. O transplante das mudas foi realizado em 26-06-2012. O delineamento experimental utilizado foi o de blocos ao acaso, com três repetições, cada repetição composta de oito plantas, sendo utilizadas as quatro plantas centrais. O filocrono foi determinado a partir do inverso do coeficiente angular da regressão linear entre o número de folhas acumuladas na haste e a soma térmica acumulada após o transplante. Observou-se linearidade entre o desenvolvimento vegetal e a temperatura média do ar nas condições do estudo. Dentre as seleções e cultivares estudadas a ‘San Andreas’ apresenta o ciclo mais precoce, necessitando de menor acúmulo de temperatura (774,70 grausdia), e a cultivar Camarosa, o ciclo mais tardio, com maior acúmulo de soma térmica (1.137,75 graus-dia). A seleção Sel1 apresentou o menor filocrono, 69,96ºC dia1 folha-1, e a cultivar Albion maior valor, 135,61 oC dia1 folha-1. Durante o período estudado, a cultivar San Andreas apresentou maior produção de frutos. ABSTRACT The objective of this study was to estimate the thermal accumulation and phyllochron of four cultivars and two selections of strawberry in theSouthern Brazil. The research was carried out in theexperimental field at the Centro de CiênciasAgroveterinárias, in the University of Santa Catarina, Lages, SC. It was used two advanced knowledge selection ofstrawberry, called ‘SEL1’ and ‘SEL2’, with plants from a public breeding program in Italy and four cultivars:Camino Real and Camarosa, with plants from Chile; San Andreas and Albion from Argentina. The transplantoccurred in 06-26-2012. The experimental design was randomized blocks with three repetitions, where theexperimental unit was composed of eight plants, using the four central plants. The phyllochron was estimated as the inverse of the angular coefficient of the linear regression between the number of stem leaf and the thermal time after transplantation. It was observed linearity between plant development and the average air temperature in the conditions of the study. Among the selections and cultivars studied the San Andreas features the earliest cycle requiring less accumulation temperature (774.70 degree-day) and the cultivar Camarosa the latest cycle with greater accumulation of thermal sum (1137.75 degree-day). The selection SEL1 had the shortest phyllochron, 69.96 oC day1 leaf-1 and the cultivar Albion higher value, 135.61 oC day1 leaf-1. During the study period the cultivar San Andreas showed higher fruit production.

The morphology of almost all grasses can be conceptualized as a hierarchical arrangement of subunits, termed phytomers. Therefore, knowledge of phytomer growth and development serves as a basis to elucidate the rhythm of grass growth. This study provides systematic analyses on the process of phytomer development of C. squarrosa, a perennial C4 grass. The invariant coordination of elongation within and between phytomers was a stable developmental feature across treatments, thus the quantitative coordination rules are applicable for predicting morphological development of C. squarrosa under contrasting levels of nitrogen nutrition or vapour pressure deficit., Phytomers are basic morphological units of plants. Knowledge of phytomer development is essential for understanding morphological plasticity, functional–structural modelling of plant growth and the usage of leaf characteristics to indicate growth conditions at the time of production (e.g. stable isotope signals). Yet, systematic analysis on the process of phytomer development is unavailable for wild or perennial C4 grasses. Also, effects of environmental factors, such as nitrogen nutrition or vapour pressure deficit (VPD), on coordination events of developmental processes of C4 grasses have not been studied. This study investigates phytomer growth and development in Cleistogenes squarrosa, a predominant C4 grass in the Eurasian steppe, grown at low (0.63 kPa) or high (1.58 kPa) VPD with low or high nitrogen supply in controlled environments. Elongation of phytomers on marked tillers was measured daily for 13 days. Then lengths of immature and mature phytomer components (blade, sheath and internode) of all phytomers were measured following dissection. Nitrogen nutrition and VPD had no effects on coordination of growth within and between phytomers: phytomer tips emerged when phytomers reached 26 % of their final length, coincident with the acceleration phase of its elongation; blade elongation stopped when phytomers reached ∼75 % of their final length and elongation of the preceding phytomer was confined to the internode. The relationship between fraction of final phytomer length and days after tip emergence for all treatments was well described by a sigmoidal function: y = 1/{1 + exp[(1.82 − x)/1.81]}. C. squarrosa exhibited little morphological plasticity at phytomer-level in response to nitrogen supply and VPD, but a clear increase in tillering under high N supply. Also, the invariant coordination of elongation within and between phytomers was a stable developmental feature, thus the quantitative coordination rules are applicable for predicting morphological development of C. squarrosa under contrasting levels of nitrogen nutrition or VPD.

Previously, we reported that phyllochron of rice greatly fluctuated in the course of development under natural conditions. The present study was carried out to examine the phyllochron dynamics using the five near-isogenic lines (NILs) for heading time and the recurrent parent. The change of phyllochron was investigated under four different controlled conditions regarding daylength and temperature. Growth duration (days to heading) showed a large variation among different growth regimes as well as genotypes. Changes of phyllochron were evaluated in the genotypes by using a quartic polynomial regression that was well fitted to the change of phyllochron in the present controlled environments as previously observed under natural conditions. Phyllochron began to drastically increase after around the 5th phytomer order and decreased with the progress of reproductive development in similar manners under different environments. The pattern of phyllochron change varied from a flat to non-flat shape. The shape of the equation was affected by genotypes as well as daylengths and temperatures. In addition, the shape was closely related to the growth duration (days to heading) of the genotype, suggesting that the phyllochron might internally increase depending on the genotype controlling the heading date. Therefore, the present results showed that the sufficient examination of phyllochron dynamics is necessary for understanding a variation in the heading date of rice.

Irrigated crops of ‘Grasslands Kaituna’ lucerne were grown for 5 years in a temperate climate at Lincoln University, Canterbury, New Zealand (43°38′S, 172°28′E). From these the response of the components of leaf area index (LAI) to environmental factors was determined. A broken stick temperature threshold with a base temperature ( T b ) of 1 °C at air temperatures ( T a ) T b = 5 °C for T a ≥ 15 was required to accumulate thermal time (Tt). Using this, the appearance of nodes on the main-stem (phyllochron) was constant in Tt within a re-growth cycle (30–42 days). The phyllochron was 37 ± 7 °Cd but declined from 60 to 37 °Cd as photoperiod decreased from 15.7 to 11.4 h. Branching began at the appearance of the fifth main-stem node with 2.5 secondary nodes produced per main-stem node in spring re-growth cycles but only 1.7 produced in summer. Leaf senescence increased from 0.3 to 1.08 leaves per main-stem node after the appearance of the ninth node. Spring re-growth cycles had a mean individual leaf area of 170 mm 2 compared with 400 mm 2 for summer re-growth cycles. These results demonstrate systematic variation in LAI components and suggest they need to be considered separately in response to environmental factors to provide a quantitative framework for crop simulation analyses of lucerne canopy development.

To gain an understanding of the adaptation of Australian and Canadian barley (Hordeum vulgare L.) cultivars to the environments of western Canada and Western Australia, phyllochron and number of leaves on the mainstem in eight cultivars of two-row, spring barley were examined when sown at two dates in two locations. The locations were a short-day environment at Northam, Western Australia, Australia in 1997 and a long-day environment at Lacombe, Alberta, Canada in 1998. At each location highly significant relationships between leaf number on the mainstem and thermal time were found (r2 > 0.94). Using linear estimates, the phyllochron of barley under short days was longer than under long days and was correlated to time to awn emergence. Later sowing shortened phyllochron under short days, but generally not under long days. Error messages from the linear regression analysis suggested that residuals were not random for all cultivars. Bilinear models were fitted to those datasets. Bilineal responses were observed under both short and long days, being independent of cultivar, date of seeding, final leaf number, phenological development pattern and time to awn emergence. The occurrence of a bilinear response was also independent of any ontogenetic events. The change in phyllochron occurred between leaves 4–7 at Northam and between leaves 6–9 at Lacombe. The leaf number at which the phyllochron change occurred was positively related to final leaf number and time to awn emergence. The phyllochron of early forming leaves was positively related to time to awn emergence and shorter than later forming leaves. Leaf emergence patterns in spring barley under both long-day and short-day conditions may therefore be linear or bilinear. Key words: barley (spring), Hordeum vulgare L., phyllochron, leaf emergence, daylength

Crop models need accurate simulation of the interdependent processes of crop development and leaf area production. Crop development proceeds according to genotype characteristics and environmental influences, specifically temperature and photoperiod. It can be partly described by thermal requirements for development intervals and coefficients that describe genotype adaptation. The objectives of this study were to (a) quantify (i) time of tassel initiation, tasselling and silking; (ii) thermal intervals for initiation, appearance and expansion of successive leaves (iii) thermal duration from initiation to tip appearance and from tip appearance to collar appearance, and (iv) leaf area and canopy cover as measured by leaf area index (LAI) in contrasting cultivars of maize grown in the field in a cool environment; and (b) relate these to plant characteristics and environmental variables, particularly temperature. For these purposes, three cultivars of maize were grown in three and four cultivars in two serial plantings from 18 April to 24 June in field experiments at Wageningen, The Netherlands, in 1997, and detailed data on crop development, leaf production and environmental variables were collected. The base temperature (T-b) for maize was confirmed as 8degreesC, but thermal time calculation needs to be re-examined to explore a recovery period after chilling injury. Equations that relate foliar properties to total leaf number and ordinal leaf position were derived. Individual leaf area can be described by the modified bell curve, and differences in temporal increase in LAI were related to parameters of leaf initiation, appearance and expansion. (C) 2002 Elsevier Science B.V. All rights reserved.

Extensive research shows temperature to be the primary environmental factor controlling the phyllochron, or rate of leaf appearance, of wheat (Triticum aestivum L.). Experimental results suggest that soil temperature at crown depth, rather than air temperature above the canopy, would better predict wheat leaf appearance rates. To test this hypothesis, leaf appearance in spring wheat ('Nordic') was measured in a 2-year field experiment (Nunn clay loam soil; fine, smectitic, mesic Aridic, Argiustoll) with three planting dates and two soil temperature treatments. One temperature treatment (denoted +3C) consisted of heating the soil at crown depth to 3 degrees C above the ambient soil temperature (denoted +0C). Main stem cumulative leaf number was measured at least weekly until flag leaf emergence. Leaf appearance was essentially linear with both air and soil growing degree-days (GDD), although there was a stronger linear relationship with soil GDD in the +0C plants than in +3C plants. A weak positive relationship between planting date and the phyllochron was observed. Unexpectedly, we found that heating the soil did not increase the rate of leaf appearance, as the paradigm would predict. To explain these results, we propose extending the paradigm in two ways. First, three processes are involved in leaf appearance: (1) cell division at the shoot apex forms the primordium; (2) cell division in the intercalary meristem forms the cells that then (3) expand to produce the leaf. Cell division is predominantly controlled by temperature, but cell expansion is considerably more affected by factors other than temperature, explaining the influence of other factors on the phyllochron. Secondly, the vertical distribution of the two meristems and region of cell expansion occur over a significant distance, where temperature varies considerably, and temperature at a specific point (e.g. crown depth) does not account for the entire temperature regime under which leaves are developing.