水稻减数分裂期颖花中激素对水分胁迫的响应

以旱A-3 (HA-3, 抗旱性品种)和武运粳7号(WY-7, 干旱敏感品种)为材料, 在减数分裂期(抽穗前15~2 d)进行充分灌溉(WW)和土壤水分胁迫(WS)处理。结果表明, WS处理显著降低叶片水势, 但穗水势没有变化。WS处理的颖花不孕率, WY-7较WW增加58.5%~50.9%, HA-3仅较WW增加12.6%~12.8%。颖花中的玉米素＋玉米素核苷、吲哚-3-乙酸和赤霉素(GA₁+GA₄)浓度在WW与WS处理间以及在两品种间无显著差异。WS显著增加颖花中脱落酸(ABA)、乙烯和1-氨基环丙烷-1-羧酸浓度。WY-7乙烯的增加超过ABA的增加, 而HA-3乙烯与ABA增加量大致相等。在减数分裂早期对WS稻穗施用氨基-乙氧基乙烯基甘氨酸(乙烯合成抑制剂)和ABA, 颖花的不孕率显著降低; 施用乙烯利(乙烯释放促进物质)和氟草酮(ABA合成抑制物质), 结果则相反。上述结果说明, 在减数分裂期遭受水分胁迫, 内源ABA和乙烯的相互拮抗作用调控颖花的育性, 较高ABA与乙烯的比值是水稻适应水分逆境的一个生理特征。

Hormones in Rice Spikelets in Responses to Water Stress during Meiosis

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.