Abstract:

The stage of meiosis is the most stress-sensitive period of reproduction in rice (Oryza sativa L.). However, the underlying biochemical mechanism is poorly understood. This study was to investigate whether and how plant hormones are involved in the regulation of spikelet sterility when subjected to water stress during meiosis. Two rice cultivars, Han A-3 (HA-3, drought-resistant) and Wuyujing 7 (WY-7, drought-susceptible), were used and subjected to well-watered (WW) and water-stressed (WS) treatments during meiosis (15-2 d before heading). Leaf water potentials of both cultivars markedly decreased during the period as a result of WS treatment, but panicle water potentials remained constant. The percentage of sterile spikelets in WS plants was increased by 48.5 to 50.9% for WY-7, whereas only by 12.6 to 12.8% for HA-3. Concentrations of zeatin + zeatin riboside, indole-3-acetic acid and gibberellins (GA₁ + GA₄) in spikelets showed no significant differences either between the WW and WS treatments or between the two cultivars. Abscisic acid (ABA), ethylene, and 1-aminocylopropane-1-carboxylic acid were all enhanced in spikelets by the water stress, with more enhanced for ethylene than for ABA in WY-7, whereas elevated ABA balanced ethylene production in HA-3. The spikelet sterility was significantly reduced when amino-ethoxyvinylglycine (an inhibitor of ethylene synthesis) or ABA was applied to the panicles of WS plants at the early meiosis stage. Application of ethephon (an ethylene-releasing agent) or fluridone (an inhibitor of ABA synthesis) had the opposite effect. The results suggest that antagonistic interactions between ABA and ethylene may be involved in mediating the effect of water stress that affects spikelet fertility. A higher ratio of ABA to ethylene would be a physiological trait of rice adaptation to water stress.

Key words:

Rice, Meiosis, Water stress, Abscisic acid (ABA), Ethylene, Spikelet sterility