Summary Plant roots exhibit diverse root functional traits to enable soil phosphorus (P) acquisition, including changes in root morphology, root exudation and mycorrhizal symbioses. Yet, whether these traits are differently coordinated among crop species to enhance P acquisition is unclear. Here, eight root functional traits for P acquisition were characterized in 16 major herbaceous crop species grown in a glasshouse under limiting and adequate soil P availability. We found substantial interspecific variation in root functional traits among species. Those with thinner roots showed more root branching and less first‐order root length, and had consistently lower colonization by arbuscular mycorrhizal fungi (AMF), fewer rhizosheath carboxylates and reduced acid phosphatase activity. In response to limiting soil P, species with thinner roots showed a stronger response in root branching, first‐order root length and specific root length of the whole root system, Conversely, species with thicker roots exhibited higher colonization by AMF and/or more P‐mobilizing exudates in the rhizosheath. We conclude that, at the species level, tradeoffs occur among the three groups of root functional traits we examined. Root diameter is a good predictor of the relative expression of these traits and how they change when P is limiting.

No abstract

No abstract

No abstract

This brief addresses the adaptive control problem for a class of pure-feedback systems with nonaffine functions possibly being nondifferentiable. Without using the mean value theorem, the difficulty of the control design for pure-feedback systems is overcome by modeling the nonaffine functions appropriately. With the help of neural network approximators, an adaptive neural controller is developed by combining the dynamic surface control (DSC) and minimal learning parameter (MLP) techniques. The key features of our approach are that, first, the restrictive assumptions on the partial derivative of nonaffine functions are removed, second, the DSC technique is used to avoid "the explosion of complexity" in the backstepping design, and the number of adaptive parameters is reduced significantly using the MLP technique, third, smooth robust compensators are employed to circumvent the influences of approximation errors and disturbances. Furthermore, it is proved that all the signals in the closed-loop system are semiglobal uniformly ultimately bounded. Finally, the simulation results are provided to demonstrate the effectiveness of the designed method.

Background and Aims Each genotype within species has a particular combination of root morphological and/or physiological traits to adapt to a phosphorus-limited environment, which can lead to its unique plant fitness and competitive ability. Yet, how the various phosphorus environments affect the competition between genotypes remains obscure.Methods Two maize (Zea mays L.) genotypes (XY335 and HMY, bred in nutrient-rich and nutrient-poor environments, respectively) were grown in monoculture and mixture in phosphorus-limited soil with homogeneous or heterogeneous supply patterns and inorganic (P inorg ) or organic phosphorus (P org ) forms. ResultsIn the homogeneous P inorg and P org environments, XY335 had higher root length and surface area, but lower mycorrhizal colonization and the acid phosphatase and phytase activities in the rhizosphere, than HMY. In the heterogeneous phosphorus environments, XY335 had higher root proliferation than HMY. The root trait divergence influenced the competition in the mixture: XY335 had a competitive advantage compared to HMY under heterogeneous phosphorus conditions, whereas HMY exhibited a stronger competitive ability in the homogeneous phosphorus treatments; these reverse trends were more significant in the P org than P inorg treatments. ConclusionsThe results suggested the importance of root physiological traits in homogeneous phosphorus-limited soil environments, whereas P acquisition strategy based on the morphological root traits favours heterogeneous phosphorus supply.

Cell growth and organ development in plants are often correlated with the tensile behavior of the primary cell wall. To understand the mechanical behavior of plant material, various mechanical testing techniques have been employed, such as tensile testing of excised tissue samples. The onion (Allium cepa L.) epidermis has emerged as a model system for plant tissue mechanics. In this study, we performed tensile tests on strips of adaxial onion epidermis. While the tissue appeared stiffer in the direction along the major growth axis compared with the transverse direction, the tensile strength of tissue was not significantly different between the two orientations, indicating a nontrivial link between the cell wall and tissue mechanical anisotropy. Importantly, we observed the stress-strain behavior of the onion epidermis under tension to be highly nonlinear. Several hyperelastic models were fitted to the test data to evaluate their capacity to describe the nonlinear deformation of onion epidermis. The Yeoh hyperelastic model could successfully simulate the uniaxial tensile test data. This study suggests that accounting for nonlinearity in the deformation of the primary tissue may be essential for the accurate interpretation of mechanical test data, and a better understanding of the mechanics of the primary plant cell wall.Résumé : La croissance cellulaire et le développement des organes chez les plantes sont souvent corrélés au comportement en traction de la paroi cellulaire primaire. Afin de comprendre le comportement mécanique de la matière végétale, plusieurs tests mécaniques ont été réalisés, tels que l'essai de traction sur des échantillons de tissus excisés. L'épiderme de l'oignon (Allium cepa L.) est apparu comme un système modèle de la mécanique des tissus végétaux. Dans cette étude, les auteurs ont réalisé des essais de traction sur des bandes d'épiderme adaxial de l'oignon. Alors que le tissu semblait plus rigide le long de l'axe principal de croissance comparativement au sens transverse, les forces de traction du tissu n'étaient pas significativement différentes entre les deux orientations, indiquant l'existence d'un lien non négligeable entre la paroi cellulaire et l'anisotropie mécanique du tissu. Fait à noter, ils ont observé que le comportement de contrainte-déformation de l'épiderme de l'oignon placé sous tension était hautement non linéaire. Plusieurs modèles hyperélastiques ont été apposés aux données expérimentales afin d'évaluer leur capacité à décrire la déformation non linéaire de l'épiderme de l'oignon. Le modèle hyperélastique de Yeoh pouvait simuler avec succès les données de l'essai de traction uniaxiale. Cette étude suggère que la prise en compte de la non-linéarité de la déformation du tissu primaire peut être essentielle à l'interprétation exacte des données d'essais mécaniques et à une meilleure compréhension de la mécanique de la paroi cellulaire primaire des plantes. [Traduit par la Rédaction] Mots-clés : épiderme, mécanique des cellules végétales, élasticité non linéaire, hyperélasti...

No abstract