Effect of foliar spray of nutrient solutions on photosynthesis, dry matteraccumulation and yield in seawater-stressed rice

The effects of seawater salinity and foliar application of nutrient solutio ns on rice in the early tillering stage and early reproductive phase of gro wth were investigated in a glasshouse. During early tillering stage, from 1 0 to 35 days after transplanting (DAT) and the early reproductive phase, fr om 75 to 100 DAT, potted rice plants were irrigated with Japan seawater of 0, 8.8, 17.5 and 35% (equivalent to an EC of 0.9, 5.7, 11.5 and 21.5 ms cm( -1), respectively). The nutrient solution of 1 mM Ca(NO3)(2), MnSO4 or K2HP O4 was sprayed twice a week until the solution ran off the leaves. Photosyn thesis and its related parameters were measured at 30 and 95 DAT in the ear ly tillering stage and in the reproductive growth phase, respectively. Seaw ater salinity diminished photosynthesis rate and photosynthesis-related par ameters, such as stomatal conductance, intercellular CO2 concentration, lea f water and osmotic potential and relative leaf water content in both growt h stages and have reduced tiller number, leaf area and top dry matter conte nt in tillering stage. We have also studied the effect of salt-stress on th e mineral content at 35 DAT. Na+ concentration increased, whereas Ca2+, Mn2 + and K+ concentration were decreased with increasing stress. Seawater decr eased fertile spikelets in the panicle, decreased accumulation of dry matte r in the grain and concomitantly decreased grain yield. Foliar spray of Ca( NO3)(2), MnSO4 or K2HPO4 partially minimized the salt-induced nutrient defi ciency, increased photosynthesis, dry matter accumulation, number of fertil e spikelet in the panicle and grain yield. Among the nutrient solutions, Ca (NO3)(2) seemed to be the most effective, followed by MnSO4 and K2HPO4. The se results suggested that foliar application of nutrient solutions partiall y alleviates the adverse effects of salinity on photosynthesis and photosyn thesis-related parameters, yield and yield components through mitigating th e nutrient demands of salt-stressed plants. (C) 2001 Elsevier Science B.V. All rights reserved.