Study on the plastic response of wheat ( Triticum aestivum L. ) root growth to P-deficiency Las revealed. There were significant negative linear relationships between the length of mot axis and internal or external P concentration of plant. The result of root-split experiment showed that the growth of mot axis was regulated by internal rather than external P concentration of plant tissue. The internal P concentration of the plant changed after plant being treated for 1 day. However, significant difference in the length of noot axis in response to different levels of P supplement occurred on the eighth day after treatment. This suggested that the change in internal P concentration of plant may be the primary response to phosphorus deficiency. In concurfence zinc concentration in shoot and IAA concentration in the whole plant increased with the decrease of P supply. The increased IAA m root promoted the growth of mot axes and the initiation of lateral mots, induced the expression of cyclin gene cyclat and subsequently the division of meristematic cells with consequent speeding up the mot extension.
小麦根系生长对缺磷胁迫的反应
孙海国! * 张福锁
（中国农业大学植物营养系，北京100094）
摘要：研究了缺磷诱导小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍＬ．）根系生长的反应，小麦根轴的生长与植株内外的磷浓度均呈显著的负线性关系。分根实验证明，随着低磷营养液中根比例的增加，在供磷水平不同的分根盒侧的根轴长度的均增加，这说明根轴生长是受体内磷浓度调控的。植株体内磷浓度的处理后１ｄ开始变化，而在不同供磷水平营养液中小麦根轴长度的差异达到显著水平的时间是处理后的第８天，说明植株体内磷浓度的变化可能是小小麦根轴生长对缺磷反应的初始原因。在植株磷对环境磷产生反应的同时，锌在体内的分配也发生了变化。小麦地上部锌浓度随着介质磷水平的降低而提高，植株生长素含量也随之增加。小麦根部生长素浓度在低磷环境中提高后，根轴长度和侧根密度明显增加，细胞周期蛋白因cyclAt的表达活性明显增强。这表明缺磷小麦根系增大是由于体内磷调节锌的分配后增加LAA含量进而诱导cyclAt基因表达的缘故； cyclAt 基因表达活性的提高，促进了根分生组织细胞的分裂，加速了根的伸展。
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