Timing of salinity stress affects rice growth and yield components

Differential sensitivity during growth stages is one of the major issues in the management of saline water for irrigation. This study was designed to analyze the effects of salinity on plant growth and yield components of ric e by composing 20-day periods of salinization at different growth stages. P lants were grown in sand tanks in a greenhouse and irrigated with nutrient solutions. Treatments were three levels of salinity with electrical conduct ivities at 1.8, 3.2 and 4.6 dS m(-1) and five timing treatments. Plants wer e salinized on the day of seeding, 1-leaf, 3-leaf, panicle initiation (PI), and booting stages, respectively, and stress was relieved after 20 days in each timing treatment. Salinity-induced reductions in shoot dry weights of plants harvested before PI were significant, but there were no significant differences among timing treatments. Reduction in shoot dry weight of plan ts harvested at seed maturity was significant only when plants were saliniz ed for a 20-day duration before booting, but not after booting. Reduction i n tiller number per plant was significant only when plants were salinized F or a 20-day duration before PI. The reductions in spikelets per panicle and seed weight per panicle were most pronounced when plants were stressed bet ween the 3-leaf and PI stages or between PI and booting stages and minor wh en stressed at the other stages. A 20-day period between 3-leaf and PI stag es was most sensitive to salinity in terms of seed yield. These results ind icate that the differential sensitivity at growth stages can be clearly sho wn when stages are well defined in the timing treatments and the stress is quantified at growth stages based on the same duration of salinization. The interaction between cultivar and timing treatment was not significant. Uni form management options can be developed for irrigation using saline water for the cultivars with similar genetic backgrounds. Published by Elsevier S cience B.V.