Individual and combined effects of waterlogging and alkalinity on yield of wheat (Triticum aestivum L.) imposed at three critical stages.

Response of wheat genotype HD 2329 to individual and combined effects of alkalinity and waterlogging (WL) at tillering, panicle emergence and anthesis stage was studied. Both stresses increased Na accumulation and reduced K uptake which leads to higher Na(+)/K(+) ratio in the leaves. Yield was decreased under all the stress treatments and highly correlated with Na(+)/K(+) ratio at all the three growth stages (r = -0.83, -0.82 and -0.73, respectively) with maximum reduction under pH 9.4 + WL. Increase in pH from 7.2 to 9.1 and 9.4 delayed complete panicle emergence (4 and 8 days) and flowering (1 and 2 days) at both, tillering and panicle emergence stages. Dual stress further increased days, required for complete panicle emergence and flowering. These results suggested that high Na(+)/K(+) ratio of plant tissue may be the critical factor for growth and development of wheat under WL, alkalinity and dual stress. Due to this delay in flowering and panicle emergence, times required for maturity of grains shorten, resulted in lower grain yield.