An automated, cost-effective and scalable, flood-and-drain based root phenotyping system for cereals

Background: Genetic studies on the molecular mechanisms of the regulation of root growth require the characterisation of a specific root phenotype to be linked with a certain genotype. Such studies using classical labour-intensive methods are severely hindered due to the technical limitations that are associated with the impeded observation of the root system of a plant during its growth. The aim of the research presented here was to develop a reliable, cost-effective method for the analysis of a plant root phenotype that would enable the precise characterisation of the root system architecture of cereals. Results: The presented method describes a complete system for automatic supplementation and continuous sensing of culture solution supplied to plants that are grown in transparent tubes containing a solid substrate. The presented system comprises the comprehensive pipeline consisting of a modular-based and remotely-controlled plant growth system and customized imaging setup for root and shoot phenotyping. The system enables an easy extension of the experimental capacity in order to form a combined platform that is comprised of parallel modules, each holding up to 48 plants. The conducted experiments focused on the selection of the most suitable conditions for phenotyping studies in barley: an optimal size of the glass beads, diameters of the acrylic tubes, composition of a medium, and a rate of the medium flow. Conclusions: The developed system enables an efficient, accurate and highly repeatable analysis of the morphological features of the root system of cereals. Because a simple and fully-automated control system is used, the experimental conditions can easily be normalised for different species of cereals. The scalability of the module-based system allows its capacity to be adjusted in order to meet the requirements of a particular experiment

Contrainte mécanique et exsudation racinaire du maïs : incidence de la morphologie du système racinaire

Not availableL’amélioration des performances agronomiques (cultures plus économes et moins agressives pour l'environnement) passe par une meilleure compréhension des mécanismes rhizosphériques. La présente étude s'intéresse à l'influence de la contrainte mécanique, liée à la compaction des sols, sur l'exsudation racinaire (exsudats solubles et mucilages). Le propos est d'évaluer la part respective jouée par la contrainte mécanique ainsi que par les modifications morphologiques induites par cette contrainte sur l'exsudation racinaire. Les travaux sont réalisés à partir d'un modèle expérimental constitué par un dispositif de culture hydroponique stérile permettant de cultiver des maïs d'âge croissant (4, 8, 12 et 16 jours) et de récolter leurs exsudats racinaires. Des billes de verre de diamètre variable (1 mm, 4 mm) permettent de simuler et de moduler l'intensité de la contrainte mécanique. Des mesures morphologiques (croissance et développement des plantes) et physiologiques de l'exsudation racinaire (techniques quantitatives et utilisation de radio-isotopes) sont entreprises. En culture hydroponique stérile, la contrainte mécanique agit principalement sur la morphologie du système racinaire, par une réduction de la longueur des racines principales et une prolifération de racines d'ordre 2, avec une biomasse inchangée. Un épaississement racinaire est mis en évidence à l'apex, zone de libération des composés exsudés. La contrainte mécanique augmente l'exsudation racinaire du maïs. D’autre part, une quantité importante de carbone se dépose à la surface des billes de verre. Ces modifications de l'exsudation racinaire peuvent être attribuées à l'effet direct de la contrainte mécanique sur les racines. Une quantification de l'exsudation racinaire du maïs jeune qui prendrait en compte les sucres, les acides aminés ainsi que les acides organiques, serait essentielle pour comprendre la réponse des plantes à la contrainte mécanique. D’autre part, une meilleure connaissance des mécanismes physiologiques (rôle hormonal) consécutifs à la présence de la contrainte mécanique est à privilégier

Plant roots release phospholipid surfactants that modify the physical and chemical properties of soil

Plant root mucilages contain powerful surfactants that will alter the interaction of soil solids with water and ions, and the rates of microbial processes. The lipid composition of maize, lupin and wheat root mucilages was analysed by thin layer chromatography and gas chromatography-mass spectrometry. A commercially available phosphatidylcholine (lecithin), chemically similar to the phospholipid surfactants identified in the mucilages, was then used to evaluate its effects on selected soil properties. The lipids found in the mucilages were principally phosphatidylcholines, composed mainly of saturated fatty acids, in contrast to the lipids extracted from root tissues. In soil at low tension, lecithin reduced the water content at any particular tension by as much as 10 and 50% in soil and acid-washed sand, respectively. Lecithin decreased the amount of phosphate adsorption in soil and increased the phosphate concentration in solution by 10%. The surfactant also reduced net rates of ammonium consumption and nitrate production in soil. These experiments provide the first evidence we are aware of that plant-released surfactants will significantly modify the biophysical environment of the rhizosphere

Root exudation of sugars, amino acids, and organic acids by maize as affected by nitrogen, phosphorus, potassium, and iron deficiency

Root exudates play a major role in the mobilization of sparingly soluble nutrients in the rhizosphere. Since the amount and composition of major metabolites in root exudates from one plant species have not yet been systematically compared under different nutrient deficiencies, relations between exudation patterns and the type of nutrient being deficient remain poorly understood. Comparing root exudates from axenically grown maize plants exposed to N, K, P, or Fe deficiency showed a higher release of glutamate, glucose, ribitol, and citrate from Fe-deficient plants, while P deficiency stimulated the release of γ-aminobutyric acid and carbohydrates. Potassium-starved plants released less sugars, in particular glycerol, ribitol, fructose, and maltose, while under N deficiency lower amounts of amino acids were found in root exudates. Principal-component analysis revealed a clear separation in the variation of the root-exudate composition between Fe or P deficiency versus N or K deficiency in the first principal component, which explained 46% of the variation in the data. In addition, a negative correlation was found between the amounts of sugars, organic and amino acids released under deficiency of a certain nutrient and the diffusion coefficient of the respective nutrient in soils. We thus hypothesize that the release of dominant root exudates such as sugars, amino acids, and organic acids by roots may reflect an ancient strategy to cope with limiting nutrient supply. Copyrigh