Root diameter decreases and rhizosheath carboxylates and acid phosphatases increase in chickpea during plant development

Abstract

Background and aims: This study investigated whether root traits at the seedling stage are maintained at the flowering stage in two chickpea (Cicer arietinum) genotypes with contrasting root morphology and physiology; and whether the genotype with greater rhizosheath carboxylates mobilises more poorly-available phosphorus (P) pools to increase shoot P at flowering/podding and seed yield at maturity. Methods: Two chickpea genotypes were grown in a low P soil with or without P addition (0 and 40 µg P g−1 soil as KH2PO4) under controlled glasshouse conditions and harvested at seedling, flowering/podding, physiological maturity. Results: At the seedling and flowering/podding stages, ICC2884 had thinner roots and greater root mass ratio, specific root length and rhizosheath carboxylates per root dry weight (DW) than ICC456. Both genotypes had smaller root diameter, higher carboxylates and acid phosphatase activity in rhizosheath soil at flowering/podding than at seedling. In the rhizosheath soil of both genotypes, NaHCO3-Pi concentration was depleted under P0 only; under both P0 and P40, NaHCO3-Po concentration increased while NaOH-Pi and NaOH-Po concentrations decreased at the seedling stage but accumulated at the flowering/podding stage, relative to the bulk soil. ICC2884 did not mobilise more poorly available soil P or acquire more P at the seedling or flowering/podding stages, or produce higher seed yields than ICC456. Conclusion: ICC2884 and ICC456 maintained the difference in root morphological and physiological characteristics from the seedling stage to the flowering/podding stage. The genotype with greater rhizosheath carboxylates (root DW basis) did not produce higher yield than genotype with less rhizosheath carboxylates.