PEG模拟干旱胁迫对3种豆科牧草种子萌发的影响

Effects of Simulated Drought Stress with PEG on Seed Germination of Three Leguminous Forage Species

[目的]探究聚乙二醇(polyethylene glycol,PEG)模拟干旱胁迫对达乌里胡枝子(Lespedeza davurica)、扁蓿豆(Medicago ruthenica)和多变小冠花(Coronilla varia)种子萌发的影响。[方法]采用浓度为0、5%、10%、15%、20%和25%的PEG溶液对3种豆科牧草种子进行模拟干旱萌发,分析发芽率、发芽指数、平均发芽时间和幼苗活力指数,并进行抗旱性综合评价,以探究在干旱胁迫下的萌发特性。[结果]随着干旱胁迫的加剧,达乌里胡枝子和扁蓿豆种子的发芽率、发芽指数和幼苗活力指数均呈显著(P<0.05)下降趋势,平均发芽时间则均呈显著(P<0.05)上升趋势,PEG浓度为25%时,达乌里胡枝子种子已失活。多变小冠花种子的发芽率、发芽指数和幼苗活力指数在PEG浓度为5%~10%时均显著(P<0.05)高于对照,之后随PEG浓度增加而呈下降趋势。采用隶属函数法综合评价发现,3种豆科牧草种子萌发期的抗旱性强弱排序为多变小冠花>扁蓿豆>达乌里胡枝子。[结论]PEG模拟干旱胁迫会抑制达乌里胡枝子和扁蓿豆种子的萌发,而低浓度(≤10%时)PEG模拟干旱胁迫会促进多变小冠花种子的萌发,高浓度(≥15%时)PEG模拟干旱胁迫则相反。多变小冠花种子的抗旱萌发能力要高于扁蓿豆和达乌里胡枝子。

[Objective] To assess the effects of simulated drought stress with polyethylene glycol(PEG) on seed germination of Lespedeza davurica, Medicago ruthenica, and Coronilla varia. [Method] PEG solutions with concentrations of 0, 5%, 10%, 15%,20% and 25% were used to simulate drought stress, and the seed germination experiments of the above three leguminous forage species were conducted. The germination percentage, germination index, mean germination time, and seedling vigor index of their seeds were analyzed, and their drought resistance were comprehensively evaluated to explore the germination properties under drought stress. [Result] The germination percentage, germination index and seedling vigor index of Lespedeza davurica and Medicago ruthenica seeds significantly(P<0.05) declined with the aggravation of drought stress, but their mean germination time significantly(P <0.05) increased. When PEG concentration reached 25%, the Lespedeza davurica seeds lost their vigor. The germination percentage, germination index and seedling vigor index of Coronilla varia seeds were significantly(P<0.05) higher than those of the control at 5%-10% of PEG concentrations, then dropped as the PEG concentrations increased. The comprehensive evaluation by membership function method demonstrated that the order of drought resistance of the three tested leguminous forage species at seed germination stage was Coronilla varia > Medicago ruthenica > Lespedeza davurica. [Conclusion]Simulated drought stress with PEG inhibits the germination of Lespedeza davurica and Medicago ruthenica seeds. PEG at low concentrations (≤10%) promote the germination of Coronilla varia seeds, however, higher concentrations (≥15%) have the reverse effect. Coronilla varia seeds have a stronger germination capacity in comparison with Medicago ruthenica and Lespedeza davurica seeds under drought stress.