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RESEARCH PRODUCT

Plant acclimation to high temperatures and water deficit: a comparative study determining independent and combined effects in four grain legume species

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National audience; Four grain legumes species (Pea, Faba bean, Lentil and Lupin) were evaluated for their responses to high temperatures (HT) and soil water deficit (WD), applied independently or jointly. We characterized both nodulated root development and growth, as well as nodulated root performance in terms of water and N uptake. To that aim, plants inoculated with rhizobium were grown up to four weeks, corresponding to their vegetative stage, in innovative RhizoTubes© on the 4PMI high throughput phenotyping platform. Most of the traits, including overall plant performance illustrated by plant biomass, were more impacted by combined HT and WD than when these stresses were applied separately. Additionally, a few root morphological traits responded specifically to either one or the other stress. Contrasted adaptive strategies mediated either through i) differential carbon partitioning among above and belowground organs, ii) root architecture plasticity or iii) the efficiency of symbiotic nitrogen fixation, were identified among the four species under individual or combined stresses. Under combined HT and WD, lupin was the only species that increased the shoot:root ratio. Under HT, lentil privileged nodule growth at the expense of root growth while the opposite occurred in lupin. Under WD, species maintained (such as faba bean or lentil) while others decreased (such as lupin of pea) nodule symbiotic fixation activity. This study highlights that the modulation by abiotic stresses of trade-offs in resource allocation between roots and nodules is not generic to the fourlegume species and that the interaction between HT and WD did not reflect additive effects of each individual stress.