【摘要】 【目的】明确水稻穗分化期高温下喷施2,4-表油菜素内酯(2,4-epibrassinolide, EBR)对穗生长及颖花形成的影响,并探究其生理机制。【方法】以热敏感型水稻IR36为材料,在幼穗分化期设置40℃高温和32℃适温两个处理,并喷施EBR,研究幼穗碳水化合物供应、蔗糖代谢、细胞分裂素代谢及抗氧化能力的变化。【结果】1)高温和适温喷施EBR,水稻每穗粒数分别比不喷施的对照增加13.7%和45.7%,其中以喷施0.15 mg/L效果最好,缓解了高温对水稻幼穗生长的抑制,增加颖花分化数和降低颖花退化率。2)喷施EBR对叶片净光合速率无显著影响,但促进幼穗中干物质和非结构性碳水化合物积累。EBR喷施增加高温下幼穗中蔗糖转运基因OsSUT1、OsSUT2和OsSUT4的表达,并显著提高蔗糖代谢相关酶活性,EBR对高温下碳水化合物利用的促进作用大于适温处理。3)喷施EBR降低高温下细胞分裂素氧化酶基因OsCKX5和OsCKX9的表达量,同时促进细胞分裂素合成和信号调节相关基因的表达,并在适温下也表现出类似的效应。4)喷施EBR降低高温下超氧阴离子含量,增强了超氧化物歧化酶、过氧化氢酶和过氧化物酶活性。【结论】高温下,喷施适宜浓度的EBR促进碳水化合物向幼穗的转运,抑制细胞分裂素分解,同时降低高温引起的过氧化伤害,进而缓解了高温对颖花形成的伤害。适温条件喷施EBR也对颖花形成具有一定的促进作用。更多还原

【Abstract】 【Objective】The purpose of the study is to ascertain the effects of 2,4-epibrassinolide(EBR) application on rice panicle development and spikelet formation under high temperature, and to explore the physiological mechanism. 【Method】Heat-sensitive inbred rice cultivar IR36 was subjected to high temperature(HT, 40℃) and normal temperature(NT, 32℃) in climate chambers with EBR application, and the carbohydrate supplement, sucrose metabolism, cytokinin metabolism, and antioxidant capacity of young panicle were investigated. 【Result】1) EBR application increased the number of spikelets per panicle by 13.7% and 45.7% on average under HT and NT, respectively, in comparison to the control. And 0.15 mg/L EBR application level performed the highest efficiency in increasing the number of spikelet number, EBR application prompted panicle development and spikelet differentiation, and inhibited spikelet degeneration. 2) EBR application did not influence leaf net photosynthesis, meanwhile increased the dry matter and nonstructural carbohydrate accumulation in young panicles. Under high temperature, EBR application significantly upregulated the expression levels of sucrose transport genes OsSUT1, OsSUT2, and OsSUT4, and EBR enhanced the related enzymes activities of sucrose metabolism especially in HT than in NT. 3) EBR application reduced the expression levels of cytokinin oxidase genes, OsCKX5 and OsCKX9, under HT. Meanwhile, EBR application promoted the genes expression involved in cytokinin biosynthesis and signal transduction both under HT and NT treatments. 4) EBR application increased the activities of superoxide dismutase, catalase and peroxidase, reduced the content of superoxide under HT. 【Conclusion】Under HT conditions, EBR application at appropriate concentration could alleviate heat damage to spikelet formation by promoting carbohydrates transportation to young panicles, inhibiting cytokinin oxidation, and reducing peroxidation injures. Meanwhile, EBR application could promote spikelet formation under normal temperature.更多还原