A significant increase in rhizosheath carboxylates and greater specific root length in response to terminal drought is associated with greater relative phosphorus acquisition in chickpea

Abstract

We investigated the effects of water stress under low phosphorus (P) supply on P-acquisition by chickpea, and identified a genotype with faster relative growth and P-acquisition rates. We grew four genotypes in pots filled with a sand and soil mixture with a low P availability in a glasshouse. Plants were either well-watered or water-stressed, imposed at the reproductive stage. Plants were harvested when water-stressed plants fully closed their stomata. For all four genotypes, water stress reduced shoot and root growth, root mass ratio, and shoot P content, while it increased specific root length (except in ICC 456), water-use efficiency and the amount of rhizosheath carboxylates per gram root dry weight. A faster relative shoot P-acquisition rate in ICC 2884 was associated with a greater specific root length, a smaller mean root diameter and a greater increase in the amount of rhizosheath carboxylates in response to water stress under low P supply. Interestingly, under water stress ICC 2884 also maintained a similar physiological P-use efficiency to that of the well-watered plants. ICC 2884 is recommended as a parental genotype in chickpea breeding programs to develop cultivars for low-P and terminal drought environments.