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Background: Plant science uses increasing amounts of phenotypic data to unravel the complex interactions between biological systems and their variable environments. Originally, phenotyping approaches were limited by manual, often destructive operations, causing large errors. Plant imaging emerged as a viable alternative allowing non-invasive and automated data acquisition. Several procedures based on image analysis were developed to monitor leaf growth as a major phenotyping target. However, in most proposals, a time-consuming parameterization of the analysis pipeline is required to handle variable conditions between images, particularly in the field due to unstable light and interferences with soil surface or weeds. To cope with these difficulties, we developed a low-cost, 2D imaging method, hereafter called PYM. The method is based on plant leaf ability to absorb blue light while reflecting infrared wavelengths. PYM consists of a Raspberry Pi computer equipped with an infrared camera and a blue filter and is associated with scripts that compute projected leaf area. This new method was tested on diverse species placed in contrasting conditions. Application to field conditions was evaluated on lettuces grown under photovoltaic panels. The objective was to look for possible acclimation of leaf expansion under photovoltaic panels to optimise the use of solar radiation per unit soil area. Results: The new PYM device proved to be efficient and accurate for screening leaf area of various species in wide ranges of environments. In the most challenging conditions that we tested, error on plant leaf area was reduced to 5% using PYM compared to 100% when using a recently published method. A high-throughput phenotyping cart, holding 6 chained PYM devices, was designed to capture up to 2000 pictures of field-grown lettuce plants in less than 2 h. Automated analysis of image stacks of individual plants over their growth cycles revealed unexpected differences in leaf expansion rate between lettuces rows depending on their position below or between the photovoltaic panels. Conclusions: The imaging device described here has several benefits, such as affordability, low cost, reliability and flexibility for online analysis and storage. It should be easily appropriated and customized to meet the needs of various users. [ABSTRACT FROM AUTHOR]

The relationships between whole-plant growth and morphogenetic processes under abiotic stresses are still partly unknown. Whole-plant biomass growth can be decreased by many abiotic stresses, including water deficit and shading. Two experiments were performed on potted plants of one grapevine cultivar (Vitis vinifera L. cv. Syrah) subjected to watering and shading treatments. Under water stress, plants reduced their primary and secondary axis leaf production rate, whereas secondary axis budburst was relatively unaffected. Individual leaf area was reduced and a strong decrease in leaf expansion rate was observed. Under shading, primary axis organogenesis was maintained, both secondary axis budburst rate and phytomer appearance rate were decreased, and individual leaf area slightly increased. Specific leaf area did not change under soil water deficit, whereas it increased under shading. These results confirm the existence of dynamic changes in organ sink strength and biomass allocation patterns to favour plant leaf area growth under shading, and to reduce plant leaf area and water losses by transpiration under water stress. From a modelling point of view, this study shows that functional structural models based on a C balance are not fully relevant for simulating plant growth under abiotic constraints if they do not include non-trophic relationships (hormonal signalling or plant hydraulic properties) that modify organ sink strength according to abiotic constraints. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is considered as an important mechanism for plants to cope with environmental challenges. Leaf growth is one of the first macroscopic processes to be impacted by modification of soil water availability. In this study, we intended to analyze and compare plasticity at different scales. We examined the differential effect of water regime (optimal, moderate water deprivation and recovery) on growth and on the expression of candidate genes in leaves of different growth stages. Candidates were selected to assess components of growth response: abscisic acid signaling, water transport, cell wall modification and stomatal development signaling network. At the tree scale, the four studied poplar hybrids responded similarly to water regime. Meanwhile, leaf growth response was under genotype × environment interaction. Patterns of candidate gene expression enriched our knowledge about their functionality in poplars. For most candidates, transcript levels were strongly structured according to leaf growth performance while response to water regime was clearly dependent on genotype. The use of an index of plasticity revealed that the magnitude of the response was higher for gene expression than for macroscopic traits. In addition, the ranking of poplar genotypes for macroscopic traits well paralleled the one for gene expression. [ABSTRACT FROM AUTHOR]

Maintaining grapevine productivity with limited inputs is crucial in Mediterranean areas. Apart from water, nitrogen (N) is also an important limiting factor in grape growing. The effects of N deficiency on grapevine growth were investigated in this study. Two-year-old Vitis vinifera L.cv. Shiraz plants grafted on 110 R were grown in pots placed outside and exposed to various N supplies (0, 0.6, 1.2, 2.4 and 12 g plant[sup -1]) under well-watered conditions. At veraison, plants were harvested and organs separately dried, weighed and analysed for N. During plant growth, the length of the primary and secondary axes and the number of leaves on them were recorded. The N content of leaves was also analysed at three phenological stages (flowering, bunch closure and veraison). All growth processes were inhibited by N deficiency in an intensity-dependent manner. Quantitative relationships with N supply were established. Vegetative growth responded negatively to N stress when comparing control N supply with no N supply: primary axis elongation (-61%), leaf emergence on the primary axis (-47%), leaf emergence on the secondary axis (-94%) and lamina area expansion (-45%). Significant differences on the plant N status were observed from flowering onwards which might be useful for managing fertilisation. Apart from water, nitrogen is also an important limiting factor in grape growing. The effects of nitrogen deficiency were investigated with 2-year-old Vitis vinifera cv. Shiraz plants grown in pots and exposed to various N supplies under well watered conditions. Primary axis elongation, leaf emergences on the primary and the secondary axes and lamina area expansion were significantly inhibited by nitrogen deficiency from flowering in an intensity-dependent manner. [ABSTRACT FROM AUTHOR]

Grapevine production and wine quality are affected by climate change, and identifying varieties adapted to climate change becomes an urgent necessity. Searching for genotypes that are more water-efficient and able to maintain high photosynthesis in drought condition seems to be the key to maintain production while preserving vineyards on the long term. In order to evaluate the genetic variability for these traits, it is a key requirement to phenotype hundreds of genotypes in the vineyard. However, this is often hampered because conventional methods for measuring water and carbon related traits are typically expensive, destructive, and not usable at high-throughput. In this project, we aimed at developing and testing new high-throughput phenotyping methods, based on the use of NIRS (Near InfraRed Spectroscopy) and leaf chlorophyll fluorescence, for studying the genetic variability and determinism of functional traits in grapevine. We used two populations, one resulting from a semi-diallel cross (600 genotypes), the other corresponding to a diversity panel of 279 Vitis vinifera varieties. In this "calibration" phase, we combined, on a subset of genotypes, conventional low-throughput measurements of photosynthesis, stomatal conductance, leaf water potential, nitrogen and carbohydrates content, with fast leaf measurements using porometry/fluorimetry and NIRS. We used these datasets to calibrate models to predict the traits of interest from NIRS and porometry/fluorimetry, based on PLS (Partial Least Squares) regressions. In the next phase of the project, we are deploying the high-throughput methods alone on the whole populations, in order to predict the traits of interest using models established in the calibration phase, and to further analyse the genetic determinants of these traits with Genome Wide Association Study (GWAS). [ABSTRACT FROM AUTHOR]

The grapevine (Vitis viniferaL.) shoot is a complex modular branching system, with one primary axis and many secondary axes organised into a repetitive structure of three successive phytomers (P0-P1-P2). P1-P2 phytomers bear one tendril or cluster, whereas P0 phytomers bear no tendrils or clusters. Axis development displays a high variability, due, partly, to trophic competition. The aim of this study was to estimate changes in trophic competition within the shoot, and to relate plasticity in axis development to changes in trophic competition. ‘Grenache N.' and ‘Syrah' cultivars were grown with two contrasting levels of cluster load. Organogenesis and organ mass were measured during shoot development. Changes in trophic competition were estimated, using the solver functions of the GreenLab model. Internodes and clusters were strong sinks. They affected the shoot development to the same extent, but the internodes showed an earlier effect. The cessation of development of the secondary axis was affected by trophic competition, but the primary axis continued to develop, regardless of trophic competition. Secondary axes differed in sensitivity to trophic competition as a function of two criteria: their type and their size. The most highly developed axes were less affected than the smaller axes, and secondary axes arising from a P0 phytomer were also less affected than secondary axes arising from a P1 or P2 phytomer. [ABSTRACT FROM AUTHOR]

The effect of trophic competition between vegetative sources and reproductive sinks on grapevine (Vitis vinifera L.) shoot development was analyzed. Two international cultivars (Grenache N and Syrah) grown in pots, which were well watered, were studied. A large range of trophic competition levels was obtained by modifying the cluster loads per plant. An analytical breakdown of the branching system was used to analyze the effects of trophic competition. Phytomer production on the primary axis and the probability and timing of axillary budburst were not affected by trophic competition. However, the duration of development and leaf production rate for secondary axes were both significantly affected. The impact of trophic competition differed within the P0–P1–P2 architectural module, locally within the shoot and between cultivars. Trophic competition reduced the organogenesis of secondary axes most strongly close to clusters, on P1–P2 phytomers and in Grenache N. Based on these results, a modeling approach simulating sink strength variation and the local effects of sink proximity would be more relevant than a model considering only development as a function of thermal time or the global distribution of available biomass. [ABSTRACT FROM AUTHOR]

Describes a method to follow rate of {14}CO—{2} and total CO—{2} production from rhizosphere respiration after plant shoots had been pulse-labelled with ∧{14}CO*mdash;{2}. Use of radioactivity detector for flow detection of beta radiation; Counting efficiency of radioactive flow cell; Applications used to trace photoassimilates within the plant-soil system.

Maintaining grapevine productivity with limited inputs is crucial in Mediterranean areas. Apart from water, nitrogen (N) is also an important limiting factor in grape growing. The effects of N deficiency on grapevine growth were investigated in this study. Two-year-old Vitis vinifera L.cv. Shiraz plants grafted on 110 R were grown in pots placed outside and exposed to various N supplies (0, 0.6, 1.2, 2.4 and 12g plant-1) under well-watered conditions. At veraison, plants were harvested and organs separately dried, weighed and analysed for N. During plant growth, the length of the primary and secondary axes and the number of leaves on them were recorded. The N content of leaves was also analysed at three phenological stages (flowering, bunch closure and veraison). All growth processes were inhibited by N deficiency in an intensity-dependent manner. Quantitative relationships with N supply were established. Vegetative growth responded negatively to N stress when comparing control N supply with no N supply: primary axis elongation (-61%), leaf emergence on the primary axis (-47%), leaf emergence on the secondary axis (-94%) and lamina area expansion (-45%). Significant differences on the plant N status were observed from flowering onwards which might be useful for managing fertilisation.

Arabidopsis thaliana (L.) Heynh. is used as a model plant in many research projects. However, few models simulate its growth at the whole-plant scale. The present study describes the first model of Arabidopsis growth integrating organogenesis, morphogenesis and carbon-partitioning processes for aerial and subterranean parts of the plant throughout its development. The objective was to analyse competition among sinks as they emerge from patterns of plant structural development. The model was adapted from the GreenLab model and was used to estimate organ sink strengths by optimisation against biomass measurements. Dry biomass production was calculated by a radiation use efficiency-based approach. Organogenesis processes were parameterised based on experimental data. The potential of this model for growth analysis was assessed using the Columbia ecotype, which was grown in standard environmental conditions. Three phases were observed in the overall time course of trophic competition within the plant. In the vegetative phase, no competition was observed. In the reproductive phase, competition increased with a strong increase when lateral inflorescences developed. Roots and internodes and structures bearing siliques were strong sinks and had a similar impact on competition. The application of the GreenLab model to the growth analysis of A. thaliana provides new insights into source-sink relationships as functions of phenology and morphogenesis.