NaCl对小麦苗叶片脯氨酸氧化酶活性和游离脯氨酸累积的影响

在含NaCl营养液中培养的小麦幼苗较之无NaCl营养液中的幼苗。其脯氨酸氧化酶活性降低,而游离脯氨酸含量则升高;培养液的渗透势越低,培养时间越长,则脯氨酸氧化酶的活性越低,且游离脯氨酸的含量越高。去除胁迫后酶活性恢复,脯氯酸含量下降。不同渗透剂对氧化酶活性抑制强弱顺序为MgCl_2>NaCl>甘露醇,引起脯氨酸累积效应的强度顺序为MgCl_2>NaCl>甘露醇。超微结构显示,高NaCl浓度下部分线粒体结构受损伤,膜和嵴部分消失。

The Effect of NaCl on Proline Oxidase Activity and Free Proline Content in Leaves of Wheat Seedlings

This paper reports the relationship between proline oxidase activity and free proline accumulation in leaves of wheat seedlings cultured in Hoagland nutrient solution containing NaCl with different osmotic potentials, as well as equiosmotic solutions of NaCl, MgCl_2 or mannitol. The changes in ultrastructure of mitochondria in seedling leaves under salt stress is also reported.The results showed that free proline content increased markedly and proline oxidase activity decreased with decreasing osmotic potential of external solution or prolonged culture time. When seedlings were alternately cultured in Hoagland nutrient solution containing or not containing NaCl, free proline content and proline oxidase activity of leaves showed significant negative correlation. Proline oxidase activity in leaves from seedlings grown in solutions with low but equal osmotic potential adjusted with NaCl, MgCl_2 and mannitol, was lower than the control to different degrees, in the order of MgCl_2 >NaCl>mannitol. And the free proline content was higher than that of the control to degrees in the same order.The ultrastructure of mitochondria of seedling leaves cultured in nutrient solution containing NaCl was damaged. Parts of their membrane and cristae disappeared, and the ultrastructure of mitochondria was damaged markedly with decreasing osmotic potential of external solution and prolonged culture time.Free proline accumulation in seedlings under salt stress may be related to the alteration of ultrastructure of mitochondria and the lowering of proline oxidase activity. The possible mechanism of proline accumulation under salt stress has been discussed.