Evaluation of potassium compared to other osmolytes in relation to osmotic adjustment and drought tolerance of chickpea under water deficit environments.

摘要

Line source sprinkling irrigation system was used to evaluate potassium (K) and other major osmolytes (sugars, proline, total amino nitrogen, and potassium) in respect with differential yielding capabilities of two groups of chickpea varieties (BR group with brown-red seed and PY group with pale yellow seed) under water deficit. Leaf water relation parameters, osmolytes, and total osmotic potential at full turgor ( Psi pi 100) were studied at early flowering (EF), late flowering (LF), and early fruiting (Eft) stages. Of the osmolytes, K accumulated in the highest amount (35 to 55% of the total Psi pi 100) in chickpea leaves regardless of growth stages and varietal groups. Varietal groups showed substantial accumulation of SPN (sugars + proline + amino nitrogen) and K with the increase in soil moisture stress irrespective of growth stages, the BR group proving to be a better accumulator of the osmolytes than PY group in most cases. However, the contribution of SPN to total Psi pi 100 increased, while that of K decreased generally with increasing soil moisture stress, particularly at Eft stage. The OA capacity of BR varieties increased, while that of PY varieties decreased significantly at EF and LF stages along the line source moisture gradient. However, potassium-contribution to OA decreased largely with the increase in water deficit and crop age. In fact, it contributed negligibly to OA at the Eft stage in case of both the varietal groups. Osmotic parameters, namely, total OA and Psi pi 100 as well as Psi pi 100 due to SPN and K, correlated linearly (P<=0.05 or P<=0.01) with seed yield, relative water content, and drought tolerance efficiency under water deficit, indicating their significant role in drought tolerance of the crop. Since BR varieties proved generally superior to PY varieties regarding all the osmotic parameters, the superior yielding capability of BR to PY varieties (26-30% yield benefit under water deficit), could be ascribed to the favorable effect of osmotic parameters on the sustenance of crop yield under water deficit. Thus, chickpea varieties could be selected for improved drought tolerance on the basis of total OA, Psi pi 100 and Psi pi 100, due to osmolytes. Moreover, the Psi pi 100, due to K, could prove as a good selecting tool; however, further research is required to know if the chickpea varieties with high efficiency of K accumulation across the growth stages are able to withstand water deficit more efficiently..