Genetic and physiological controls of growth under water deficit
Résumé
The sensitivity of expansive growth to water deficit has a large genetic variability, higher than that of photosynthesis. It is observed in several species, with some genotypes stopping growth in a relatively wet soil while others continue growing until the lower limit of soil available water. The responses of growth to soil water deficit and to evaporative demand share an appreciable part of their genetic control via the co-location of quantitative trait loci (QTLs), and so do the responses of the growth of different organs to water deficit. This may be due to common mechanisms of action discussed in this paper, in particular plant hydraulic properties. We propose that expansive growth, putatively linked to hydraulic processes, determines the sink strength under water deficit, while photosynthesis determines source strength. These findings have large consequences for plant modeling under water deficit and for the design of breeding programs.