渗透胁迫下不同抗旱性小麦幼苗氨同化差异

在渗透胁迫下，测定了不同抗旱性小麦（抗旱性强的品种洛旱6号和抗旱性弱的品种周麦18）幼苗氨同化酶及相关参数的变化.结果表明:小麦生物量在渗透胁迫下明显降低，且抗旱性弱的周麦18降幅较大.铵态氮含量随胁迫程度的增加而增加，且周麦18增加较明显；谷氨酰胺合成酶(GS)活性在不同抗旱性品种间表现不同，抗旱性强的洛旱6号在低渗透胁迫下显著增加，在高渗透胁迫下明显降低，而周麦18随胁迫程度的增加逐渐降低；依赖还原型辅酶Ⅰ的谷氨酸脱氢酶(NADH-GDH)活性随胁迫程度的增加逐渐加大，低渗透胁迫下周麦18增加较明显，高渗透胁迫下洛旱6号增幅较大；依赖氧化型辅酶Ⅰ的谷氨酸脱氢酶(NAD^+-GDH)和依赖氧化型辅酶Ⅱ的异柠檬酸脱氢酶(NADP-ICDH)活性均随胁迫程度的增加而增加，周麦18的NAD^+-GDH活性、洛旱6号的NADP-ICDH活性增幅较大.表明小麦抗旱性的提高与铵态氮同化的增强有关，低渗透和高渗透胁迫下分别依赖GS和NADH-GDH活性的增加.

Difference in seedlings ammonium assimilation of wheat cultivars with different drought resistance under osmotic stress

Taking wheat cultivars drought-resistant Luohan-6 and drought-sensitive Zhoumai-18 as test objects, their seedlings ammonium assimilation enzyme activities and related parameters were determined under osmotic stress. The plant biomass had an obvious decrease under osmotic stress, with a larger decrement for Zhoumai-18 than Luohan-6. Osmotic stress increased the plant ammonium content, especially for Zhoumai-18. The glutamine synthetase (GS) activity varied with wheat cultivars. For Luohan-6, the GS activity increased significantly under low osmotic stress but decreased under high osmotic stress; while for Zhoumai-18, the GS activity decreased with increasing osmotic stress. The NADH-dependent glut
amate dehydrogenase (NADH-GDH) increased with increasing osmotic stress, with a marked increment under low osmotic stress for Zhoumai-18, and under high osmotic stress for Luohan-6. The NAD^+-dependent glutamate dehydrogenase (NAD^+-GDH) and NADP-dependent isocitrate dehydrogenase (NADP-ICDH) activities also increased with increasing osmotic stress, with a greater increment of NAD^+-GDH activity for Zhoumai-18, and of NADP-ICDH activity for Luohan-6. It was suggested that the increased drought resistance of wheat plants could be related to the incre
ased ammonium assimilation resulted from the enhanced GS and NADH-GDH activities under low and high osmotic stress, respectively.