渗透胁迫下小麦根系渗透调节与根冠淀粉水解的研究

Osmotic Adjustment in Wheat Roots and Hydrolysis of Starch in Root-cap of Wheat under Osmotic Stress

用不同浓度的PEG-600对抗旱性不同的小麦幼苗进行渗透胁迫处理,研究了小麦幼苗根系的淀粉酶活性、可溶性糖含量、渗透势、渗透调节能力和根冠淀粉的水解状况.结果表明,随着渗透胁迫程度的加重,抗旱性强的小麦品种昌乐5号和北农2号根系渗透势和饱和渗透势的降低程度大于抗旱性弱的小麦品种鲁麦5号和921842,并且抗旱性强的小麦品种根系的渗透调节能力大于抗旱性弱的小麦品种.随着渗透胁迫程度的加重,各品种小麦根冠淀粉粒均有不同程度的减少,而抗旱性强的品种根冠淀粉粒的减少程度小于抗旱性弱的品种;抗旱性强的小麦品种根系淀粉酶活性显著高于抗旱性弱的小麦品种,但是,随着渗透胁迫程度的加重,抗旱性弱的品种淀粉酶活性增加的幅度远高于抗旱性强的品种.可溶性糖含量的变化趋势与淀粉酶活性的变化趋势一致,即渗透胁迫下根冠淀粉水解程度大的小麦品种,可溶性糖的含量高.但根冠淀粉水解在根系的渗透调节以及在小麦适应水分胁迫中的作用还有待于进一步探讨.

Wheat cultivars,CHL5 and BN2(drought-resistant ),LM5 and 921842 (drought-sensitive),were used in the study. Different concentrations of PEG-6000 were used to induce different osmotic stress conditions. The activity of amylase, content of soluble sugar, osmotic potential, ability of osmotic adjustment as well as hydrolysable level of starch in root cap were studied in wheat roots under osmotic stress. It was demonstrated that with the increase of osmotic stress, the osmotic potential and saturation osmotic potential in roots of drought-resistant cultivars decreased more than those of drought-sensitive cultivars, and this indicated that the drought-resistant cultivars had greater ability of osmotic adjustment than drought-sensitive cultivars. The content of starch in root cap decreased with the increase of osmotic stress in all cultivars, and the decrement was lower in drought-resistant cultivars than that in drought-sensitive cultivars. The activities of root amylase in drought-resistant cultivars were significantly higher than those in drought-sensitive cultivars but the activities of the latter were much more enhanced by the increase of osmotic stress. The changes of soluble sugar were consistent with the changes of amylase. The hydrolysis level of starch near root-cap was in agreement with the soluble sugar content under osmotic stress. However,the roles of hydrolysis of root starch in root osmotic adjustment and in drought adaptation of wheat need further studies.