外源NO调控盐胁迫下蒺藜苜蓿种子萌发生理特性及抗氧化酶的研究

Effects of exogenous nitric oixde on seed germination,physiological characteristics and active oxygen metabolism of Medicago truncatula under NaCl stress

本试验以蒺藜苜蓿种子为材料,预先用0.1,0.3和1.0mmol/L硝普钠(SNP,NO供体)浸种,通过计算相关萌发指标,测定种子萌发过程中各项生理指标及抗氧化系统酶活性,研究外源NO对2.0%NaCl胁迫下蒺藜苜蓿种子萌发生理特性及活性氧代谢的影响。结果表明,0.1mmol/L SNP能显著缓解盐胁迫对蒺藜苜蓿种子造成的伤害,使蒺藜苜蓿种子的发芽率、发芽势、发芽指数和活力指数分别提高了333.40%,79.64%,171.93%和100.00%;种子可溶性糖、可溶性蛋白和脯氨酸含量分别提高了21.1%,42.3%和123.1%,淀粉含量降低了17.7%,淀粉酶活性提高了29.7%,丙二醛(MDA)和超氧阴离子(O2-·)含量分别降低了21.8%和27.2%,超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性和抗坏血酸过氧化物酶(APX)活性分别增加了28.6%,43.1%,56.2%和60.3%;与0.1mmol/L SNP处理相比,0.3mmol/L SNP处理对盐胁迫下蒺藜苜蓿种子萌发的促进、氧化损伤的缓解和抗氧化系统酶活性的提高显著降低;1.0mmol/L SNP处理对盐胁迫下蒺藜苜蓿种子的萌发起到抑制作用。说明低浓度的NO可通过降低种子MDA和O2-·含量,提高种子脯氨酸含量以及激活抗氧化系统酶活性,减轻盐胁迫对蒺藜苜蓿种子的伤害,促进淀粉、可溶性蛋白的水解,从而加速种子萌发。

Medicago truncatula seeds were pre-soaked with 0. 1, 0. 3 and 1. 0 mmol/L sodium nitriprusside [SNP, a nitric oxide （NO） donor] solution to study the effects of nitric oxide on seed germination, physiological characteristics and active oxygen metabolism of M. truncatula under 2. 0% NaCl stress. Damage to M. truncatula seeds caused by 2.0 % NaCl stress was significantly alleviated in the presence of 0.1 mmol/L SNP. The seed germination percentage, germination energy, germination index and vigor index were increased 333.40% ,79.64%,171.93% and 100.00%, respectively; while soluble sugar, protein and proline contents in seeds were increased by 21.1%, 42.3% and 123.1%, respectively. Starch content was decreased by 17.7%, amylase activity was increased by 29.7%, andMDAand O2-· contents were decreased by 21.8% and 27.2%,respectively. Activities of SOD, POD, CAT and APX in seeds were increased by 28.6%, 43.1%, 56.2%and 60.3%, respectively. Seed germination, oxidative damage and the antioxidant enzyme activities in seeds de- creased when seeds were treated with 0.3 mmol/L SNP. When the concentration of SNP solution was increased to 1.0 mmol/L, we observed an inhibitory effect on seed germination. Our results provide evidence that lower concentrations of SNP may alleviate damage to seeds caused by salt stress. Key components of the response are. decreased MDA and O2-· levels, increased proline level and antioxidant enzyme activities in seeds, with resultant promotion of starch and protein hydrolysis, expedition of seed germination.