Enhancement mechanism of chilling torelance induced by a novel steroidal phytohormone, brassinosteroid.

本文研究了油菜素内酯增强油菜耐冷性的机理。在寻找低温胁迫信号转导时，水稻幼苗的敏感性高于黄瓜幼苗。在低温胁迫条件下，油菜素内酯对根生长的影响显著。油菜素内酯在低温胁迫前处理比同时处理和胁迫后处理更有效。油菜素内酯处理后的根组织氧化活性明显增强。这说明油菜素内酯促进了根系的生长，增加了根系对养分的吸收，从而激活了低温胁迫响应的信号转导系统。湿度，特别是保持较低的湿度，是提高油菜素内酯效果的重要因素。油菜素内酯活性持续时间较短，说明外源处理的油菜素内酯在幼苗体内代谢迅速。在黄瓜幼苗中，油菜素内酯很容易被外聚成与油菜素内酯具有相同分子的异构体，然后转化为与糖和/或脂肪酸偶联的共轭物。化学衍生化后，对该缀合物及其苷元的结构进行了理化分析，并将其光谱数据与几种可能的化学合成化合物和黄瓜细胞悬浮培养诱导的代谢物进行了比较。尽管进行了分析，但对结构的测定尚未得到证实。另一方面，几种与生长素活性几乎相同的酸性油菜素内酯化合物在叶面关节试验中也具有相同的活性。耐寒性和耐久性必须得到确认。

This is study on a mechanism of chilling tolerance enhancement induced by treatment with brassinolide. Rice seedling was higher than that of cucumber seedling in sensitivity when searching a signal transduction of the chilling stress. Effect of brassinolide was appeared remarkably in the root growth under the chilling stress condition. The timing of brassinolide treatment was more effective with pre-treatment before the seedling was put in the chilling stress condition than with simultanious treatment or post- treatment after in the stress condition. Oxidation activity was strongly increased in the brassinolide-treated root tissue. This suggests that brassinolide promotes the growth of root and enhances nutrient absorption from root, so that a signal transduction system for the chilling stress response is activated. Humidity, especialy to keep it lower, was important to enhance the effect of brassinolide. Durability of brassinolide activity was short and it shows that brassinolide treated exogenously was rapidly metabolited in the seedling. In cucumber seedling brassinolide was easily epimerized to an isomer possessing the same molecular as brassinolide and then it was converted to conjugate coupled with a sugar and/or a fatty acid. The structures of the conjugate and its aglycone were undertaken to physicochemical analyses after chemical derivatization and also their spectral data were compared with several presumable compounds synthesized chemically and metabolites induced by cucumber cell suspension culture. In spite of them analyses determination of the structures have been not elicidated. On the other hand, several compounds of acid brassinolide with almost same activity as auxin in the lamina joint test. Chilling tolerance activity and its durability must be confirmed.