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为了明确黄瓜(Cucumis sativus L.)子叶和顶芽在幼苗下胚轴不定根发生中的作用,采用琼脂培养基扦插的方法,研究了子叶和顶芽的去留对下胚轴基部内源IAA和GA3积累水平及不定根发生的影响。结果表明,子叶对下胚轴不定根的发生非常关键。保留双子叶的幼苗下胚轴基部IAA含量呈先升高后降低的趋势,GA3呈先降低后升高的趋势,不定根正常发生;去除单片子叶,下胚轴基部IAA和GA3积累显著减少,不定根发生相关基因及IAA、GA3响应基因(Cs ARL1、Cs GH3.5、Cs GASA4等)表达水平降低,不定根发生区缩小、数量减少;去除双子叶,下胚轴基部IAA和GA3无法积累,不定根不发生。顶芽去留对下胚轴不定根发生没有显著影响。外源施用IAA可以部分缓解因去除单片子叶对不定根发生的抑制作用,喷施IAA极性运输抑制剂,下胚轴不定根发生受到抑制;与IAA不同,外源施用GA3抑制下胚轴不定根发生,喷施GA合成抑制剂促进不定根发生,GA对IAA响应基因具有负调控作用,表明子叶合成的IAA是诱导下胚轴不定根发生的关键。去除双子叶时,无论单独或交互施用IAA与GA3,均不能诱导下胚轴形成不定根,表明IAA并非不定根发生的唯一诱因。进一步分析发现去除子叶后下胚轴基部可溶性蛋白质和可溶性糖含量显著降低,可能是影响不定根发生的其他因素。子叶作为黄瓜幼苗生长素、蛋白质和糖的主要合成和输出源,对黄瓜幼苗下胚轴不定根发生起关键作用。
In order to clarify the role of cotyledons and terminal buds of cucumber (Cucumis sativus L.) in adventitious root formation of hypocotyls in seedlings, we studied the effect of cotyledon and terminal buds on endogenous IAA and GA3 accumulation and adventitious root formation. The results showed that cotyledon was the key to adventitious root formation in hypocotyls. The content of IAA in the hypocotyls of the seedlings retained the trend of first increasing and then decreasing, GA3 first decreasing and then increasing, adventitious roots normally occur; the accumulation of IAA and GA3 in the base of hypocotyls significantly decreased after removal of monocotyledon, The expression of adventitious root, IAA and GA3response genes (Cs ARL1, Cs GH3.5, Cs GASA4, etc.) decreased and the number of adventitious root formation decreased and the number of adventitious roots decreased; the IAA and GA3 at the base of hypocotyls could not accumulate and adventitious roots Does not happen. There was no significant effect of adventitious buds on the hypocotyls. Exogenous application of IAA could partially alleviate the inhibition of adventitious root formation due to the removal of monocotyledonous leaves. Spraying IAA polar transport inhibitor inhibited the adventitious root formation of hypocotyls. Exogenous IAA, GA3 inhibited the adventitious root formation GA could inhibit adventitious root formation. GA had negative regulation on IAA response gene, indicating that IAA synthesized from cotyledon was the key factor inducing adventitious root formation. When dicotyledon was removed, neither IAA nor GA3 alone or in combination could induce adventitious bud formation in hypocotyls, indicating that IAA is not the only cause of adventitious root formation. Further analysis showed that the content of soluble protein and soluble sugar in the base of hypocotyls after removal of cotyledons was significantly decreased, which may be other factors that affect adventitious root formation. Cotyledon, as the major auxin and source of auxin, protein and sugar in cucumber seedlings, played a key role in adventitious root formation of cucumber seedling hypocotyls.