Root functioning, carbon allocation and tolerance to water stress in Pea (Pisum sativum)
Résumé
Pea crop (Pisum sativum, Fabaceae) is threatened by increasing drought, which can reduce yield due to carbon competition between roots and seeds. Pea crop is usually exposed to water stress during flowering. This can lead to flower and seed abortions, reducing crop productivity. However, drought episodes are now occurring earlier, affecting pea crop in its vegetative development and impacting root system establishment. To improve drought tolerance, it’s now crucial to focus on root plasticity, especially at early stages of development and explore how carbon fluxes can be modulated in legume breeding programs. The aim of our study is twofold. Firstly, to study the role of root development in plant tolerance to water stress. Secondly, to characterise the beneficial effects of biostimulant products on plant responses to water stress. To this end, 11 spring protein pea cultivars were grown in Rhizobox systems, enabling direct observation of the root system architecture to identify contrasting responses to water deficit at early developmental stages. In some cultivars, a developmental delay to reach the 2-leaf stage was observed under water deficit. Using the SmartRoot software, we performed dynamic root system monitoring over a developmental time-course on five cultivars showing contrasting responses to water deficit. Our results suggest that, at early developmental stages, the shape of the root system is remodelled at fine scale under water deficit, without change in biomass output. Then, three biostimulant protocols were tested and one of them showed significant results in mitigating the impacts of water stress during flowering. These included a reduction in the growth arrest during water stress and an increase resilience in seed production during the period of water recovery. These findings can support the development of new agroecological strategies to increase pea yield by focusing on carbon fluxes in the context of climate change.