马银花种子萌发期对干旱胁迫的生理响应

Physiological Responses of Rhododendron ovatum to Drought Stress during Its Seed Germination Stage

以马银花为材料,采用聚乙二醇（PEG-6000）模拟不同程度的干旱胁迫,观测马银花种子发芽率、抗氧化酶活性、有机渗透调节物质、丙二醛（MDA）含量及细胞膜相对透性的变化,探讨马银花种子萌发期对干旱胁迫的生理生化响应机制。结果表明：（1）PEG胁迫浓度≥15%时,马银花种子萌发率显著降低,种子萌发受抑制。（2）5%～20% PEG胁迫浓度范围内,随着干旱胁迫程度的增加,超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性先升后降,均在15% PEG胁迫下达到最高;过氧化物酶（POD）活性持续升高。（3）与对照（CK）和轻度胁迫（5%、10% PEG）相比,15%～20% PEG胁迫下脯氨酸含量、可溶性糖含量、MDA含量和细胞膜相对透性均显著升高。说明种子萌发期的马银花具有一定的耐旱性,可抵御轻度水分胁迫;15% PEG中度水分胁迫下马银花种子萌发受抑制,但可通过自身生理指标的改变主动适应干旱逆境。

In order to study the physiological and biochemical response mechanism of Rhododendron ovatum to drought stress during its seed germination stage,the dynamics of germination rate,antioxidant enzyme activities,organic osmoregulation substances,malondialdehyde（ MDA） and relative permeability of cell membrane were analyzed under drought stress simulated by polyethylene glycol（ PEG）-6000. The results showed that germination rate of R.ovatum was significantly decreased and inhibited when PEG stress concentration was≥15%.At 5%-20% PEG stress concentration,SOD and CAT activities were increased when PEG was≤15% but decreased when PEG was 〉15%,POD activity was continuously increased with the increase of drought stress degree.In comparison with no stress（ CK） and light drought stress,the contents of proline,soluble sugar and MDA and relative permeability of cell membrane increased significantly. The results indicated that seed germination of R.ovatum was tolerant to drought in some degree under light water stress. The seed germination of R.ovatum was inhibited by moderate water stress（ 15% PEG）,but the seeds could adapt to drought stress by changing their own physiological conditions.