Keywords :

Plant architecture and in-plant water supply and transfer

Water supply has a marked impact on plant functioning in terms of resource acquisition (water/mineral uptake and photosynthesis), assimilate allocation to different organs and therefore control of organ growth.

A plant water uptake and transfer model was developed. This model is based on plant architecture descriptions combined with characterization of plant axis hydraulic functioning (uptake and transfer capacities). The axis type and diameter are simple relevant indicators for describing hydraulic conductivity variations and for constructing a hydraulic architecture for both the roots and above-ground parts. Boundary conditions are imposed at the soil-root interface in terms of the water potential and at the leaf level in terms of transpiration flow. Combining the plant architecture and its hydraulic functioning enables description of water uptake and transfer in the plant via characterization of the water potential distribution. The water potential seems to be highly variable in plants, with gradients that vary according to the water availability. Below-ground simulations enable localization of water uptake in the root system as a function of the architectural and uptake characteristics of different root types. The spatial heterogeneity of the soil water supply, as a function of the soil depth or distance from irrigation drippers, also markedly determines the spatialization of water extraction with, for instance, gradual displacement of the wetting front with drying of the soil surface. The above-ground water potential is not uniform, with more negative potentials in the foliage. This water uptake and transfer model in a functional architecture was combined with a fruit growth model which enables description of part of the observed variability in fruit growth and composition.