外源NO提高小麦幼苗抗旱性的生理机制

Mechanism of Exogenous Nitric Oxide Enhancing Drought-Resistance of Wheat Seedlings

以小麦(Triticum aestivum L.)品种‘豫麦49’为材料,采用50μmol·L-1SNP(NO供体)处理自然干旱和PEG模拟干旱下的小麦幼苗,分析外源NO对水分胁迫下小麦幼苗相对含水量、光合速率、细胞膜透性以及茎叶中关键性离子含量的影响。结果显示:自然干旱10d后,对照组幼苗几乎全部枯死,而50μmol·L-1SNP处理幼苗并未发生枯死,其幼苗在旱后复水2d后能完全恢复正常生长;在25%PEG-6000模拟干旱条件下,50μmol·L-1SNP处理也能明显改善受胁迫小麦幼苗长势。50μmol·L-1SNP处理使模拟干旱胁迫下小麦叶片的相对含水量显著提高15.98%,净光合速率(Pn)、气孔导度(Gs)分别显著提高47.11%和42.86%,而胞间CO2浓度(Ci)显著降低了8.19%;也使小麦组织浸出液电导率显著降低30%,茎叶的K+含量显著增加24.55%(P<0.01)。研究发现,外源NO既可通过降低小麦幼苗叶片蒸腾来维持较高的叶片相对含水量,缓解因干旱缺水对植株的伤害;又可增加K+在茎叶中积累,减轻干旱胁迫对小麦幼苗细胞膜伤害,维持干旱胁迫下小麦幼苗较高的光合速率,以确保植株正常生长和有机物质积累。

Wheat （Triticum aestivum L. ） variety, ‘Yumai 49＇ seedlings were treated with 50 μmol·L^-1 SNP （NO donor） under drought stress or mimic drought stress. The effect of exogenous nitric oxide （NO） on relative water content, photosynthetic rat, permeability of cell membranes and contents of the key ion as K＋ were investigated in wheat seedlings under water stress. After 10d of drought stress,the wheat seed- lings pretreated with water as control, were almost dead, but which pretreated with 50μmol·L-1 SNP grew better. The latter fully return to normal growth after the resumption of water for 2 d;In experiments of 25 % PEG-6000 mimic drought stress, the similar results were obtained. The treatment with 50μmol·L-1 SNP increased the RWC of wheat leaves by 15. 98%. The transpiration rate was decreased a 45% with SNP treatment at the same analyzed time. In addition,the treatment with 50 μmol·L^-1 SNP increased the net photosynthetic rate （Pn） and stomatal conductance （Gn） by 47.11% and 42. 86% respectively,but intercellular CO2 concentration （Ci） was decreased by 8.19% ,compared with 25% PEG-6000 treatment. The relative electrolytic leakage,a cell injury index,was 30 % lower in SNP treated wheat seedlings than that with 25% PEG-6000 treatment. Meanwhile, we measured K＋ content in wheat shoots and the results showed that the treatment with 50 μmol· L^-1 SNP increased K＋ content by 24. 55%（P〈0.01） under mimic drought stress, which is good for wheat seedlings against drought stress. These results indicated that exogenous NO decreased transpiration rate and maintained a relatively high water content in wheat to alleviate the water shortage. Meanwhile,the treatment alleviated wheat seedlings cell injury, increased the accumulate of the key ion as K＋ in the stems and leaves, and maintained higher photosynthetic efficiency to ensure normal growth of plant and accumulation of organic matter in response to drought stress.