干旱胁迫对栓皮栎种子萌发能力的影响

Effect of drought stress on seed germination ability of Quercus variabilis Bl.

【目的】揭示栓皮栎种子萌发对干旱环境的适应能力。【方法】采用不同质量浓度的聚乙二醇(PEG-6000)模拟不同程度的干旱胁迫(-0.1,-0.3,-0.6,-0.9,-1.2,-1.5 MPa),以蒸馏水为对照,研究栓皮栎种子萌发能力及生理生化指标对干旱胁迫的响应,并对种子萌动、萌芽与出苗的环境水势予以定量分析。【结果】(1)在-0.1 MPa时,栓皮栎种子萌发率、萌发势和胚根长均高于对照,且种子萌发启动时间、萌发指数、活力指数与对照无明显差异;在-0.3^-0.9 MPa时,各项萌发指标值均明显低于对照,但萌发率仍保持在52.95%~20.43%;在-1.2^-1.5MPa时,种子几乎不能萌发。当环境水势高于-1.2MPa时,栓皮栎可通过增大根芽比适应干旱环境。(2)栓皮栎种子从萌动到萌芽再到出苗的过程,对环境水分状况逐渐敏感,水势依次为-0.12,-0.08和-0.06 MPa。(3)干旱导致栓皮栎种子内丙二醛含量增加。在-0.1^-0.9 MPa时,3种有机渗透调节物质(脯氨酸、可溶性糖、可溶性蛋白)含量呈现不同的变化,但均显著高于对照;在-1.2^-1.5 MPa时,可溶性糖和可溶性蛋白含量均有不同程度减少,其中可溶性蛋白含量在-1.2 MPa时就开始低于对照,而可溶性糖在-1.5 MPa时才低于对照。在-0.1^-0.6 MPa时,抗氧化酶活性(超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX))和抗坏血酸(ASA)含量升高;在-0.9 MPa时,POD活性和ASA含量降低;而-1.2^-1.5 MPa时抑制了SOD、CAT、POD、APX活性的增加,ASA含量也显著下降。【结论】当环境水势不低于-0.9 MPa时,栓皮栎种子可以通过调节生理功能萌发,但超出其耐受力则不能萌发成苗;水分条件是阻碍黄土高原干旱半干旱地区栓皮栎种群更新与造林成败的因素之一。

[Objective] This paper investigated the adaptive capability of Quercus variabilis B1. seed to draught stress. [Method] The research investigated the responses of germination, physiological and bio- chemical indexes of Quercus variabilis B1. to drought stress simulated by different mass concentrations of polyethylene glycol （PEG）-6000 （-0.1, -0.3, -0.6, -0.9, - 1.2, and - 1.5 MPa）, and distilled waterunder -0.1 to -0.9 MPa,but all were significantly higher than under control. Soluble sugar and protein reduced under - 1. 2 to - 1. 5 MPa. Soluble protein began to decrease to lower than the control under -1.2 MPa,while soluble sugar did not reduce until under -1.5 MPa. Activities of superoxide dismutase （SOD）,catalase （CAT）, peroxidase （POD） and ascorbate peroxidase （APX）, and ascorbic acid content （ASA） increased under -0.1 to -0.6 MPa,while the activity of POD and ASA content declined under -0.9 MPa. All antioxidant enzymes activities and ASA content were suppressed under -1. 2 to -1. 5 MPa. [Conclusion] Q. variabilis B1. seed could adapt to drought stress through its own biological and phys- iological changes to sprout seedling under no less than -0.9 MPa drought stress,but seed could not germi- nate beyond its drought tolerance. The water condition is a key factor restricting Q. variabilis B1. popula- tion natural regeneration and afforestation in arid and semi arid area of the Loess Plateau.