Effect of water regime on growth, yield and hormonal changes in MR 220 rice variety during reproductive stage

H. Shahida and C.S. Chan

Abstract
This study was conducted in a plant house at MARDI Seberang Perai. The objectives of this study were to determine endogenous plant hormones that are involved in the regulation of spikelet sterility, particularly when exposed to different water regimes during reproductive stage (the most sensitive period to water stress) and to determine the effect of exogenous hormone/hormones to the spikelet sterility. In this study, MR 220 was used and subjected to different water regimes, namely flooded, saturated and aerobic soil conditions. Number of productive tiller, tiller mortality, grain yield, percentage of filled grain and harvest index were significantly influenced by the water regimes tested. Abscisic acid (ABA) level was significantly higher when plants were grown under aerobic soil condition and its level remained slightly constant in the spikelets of plants grown under flooded and saturated soil conditions. However, no significant effects were shown by water regimes on levels of indole-3-acetic (IAA) and gibberellic acid (GA3). Application of exogenous ABA to the plant increased the percentage of filled grain particularly when plants were grown under aerobic soil condition while application of ABA inhibitor, fluridone, significantly reduced the percentage of filled grain for all water regimes tested.

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