干旱胁迫对鹿角杜鹃种子萌发和幼苗生理特性的影响

为探明鹿角杜鹃种子萌发和幼苗生长期的耐旱性,以鹿角杜鹃干种子和90d苗龄幼苗为材料,采用聚乙二醇(PEG-6000)模拟不同程度的干旱胁迫,研究干旱胁迫对其种子萌发、早期幼苗生长及幼苗的细胞膜透性、MDA含量、有机渗透调节物质和抗氧化酶活性的影响,并对种子萌发率、早期幼苗生长量与PEG胁迫浓度间进行了回归分析。结果表明:(1)5%~25%PEG胁迫范围内,随着干旱胁迫程度的增加,鹿角杜鹃种子的发芽启动时间推迟,发芽持续时间延长,发芽率、发芽势、发芽指数、活力指数和幼苗生长量显著降低;重度干旱胁迫(25%PEG)下,鹿角杜鹃种子完全未萌发。(2)发芽率、发芽势、发芽指数、活力指数以及幼苗生长量的变化均与干旱胁迫程度呈极显著负相关关系,回归分析求得鹿角杜鹃种子萌发的半致死PEG干旱胁迫浓度为15.68%、半致矮PEG干旱胁迫浓度为15.37%。(3)随着PEG胁迫浓度的增加,鹿角杜鹃幼苗叶片SOD活性呈先升后降的趋势,但各胁迫处理仍显著高于CK(0%PEG);细胞膜透性、MDA、脯氨酸、可溶性糖含量、POD和CAT活性则在中度(15%~20%PEG)和重度胁迫下显著升高,与干旱胁迫程度呈极显著正相关关系。研究表明,干旱胁迫显著抑制了鹿角杜鹃种子萌发和早期幼苗生长,使其细胞膜受到损伤,同时鹿角杜鹃可通过体内渗透调节物质和抗氧化酶活性的增加来适应干旱环境,使得自身受抑制、损伤程度降到最低。

Effects of Drought Stress on Seed Germination and Seedling Physiological Characteristics of Rhododendron latoucheae

In order to explore the drought tolerance of Rhododendron latoucheae in seed germination and seedling growth stage,we studied the effects of drought stress on seed germination,growth,cell membrane permeability,malondialdehyde(MDA) content,the organic osmoregulation substances and antioxidant enzyme activities by choosing dry seeds and seedlings with 90 d age and using different concentrations of polyethylene glycol(PEG-6000) simulated drought stress.The regression analyses were done between seed germination,early seedling growth and PEG stress.The results showed that:(1)the initial germination time of R.latoucheae seeds was delayed with the increasing of drought stress degree in 5%-25% PEG range,and the germination duration was prolonged.The seed germination rate,germination potential,germination index,vigor index and early seedling growth were all significantly reduced.The seed could not germinate absolutely at severe drought stress(25% PEG).(2)The changes of seed germination rate,germination potential,germination index,vigor index and early seedling growth were showed very significant negative correlation with the degree of drought stress.The regression equation between seed germination,early seedling growth and PEG stress showed that the half lethal PEG drought stress concentration was 15.68%,while the semi dwarfing PEG drought stress concentration was 15.37%.(3)With the increase of PEG concentration,SOD activity of R.latoucheae seedling leaves increased firstly and then decreased,but were significantly higher in all the stress treatments than that of CK(0% PEG).Cell membrane permeability,MDA content,proline content,soluble sugar content,POD and CAT activities increased significantly in moderate(15%-20% PEG) and severe drought stress,and the changes of these indexes were showed very significantly positive correlation with the degree of drought stress.The research found that seed germination and seedling growth of R.latoucheae were significantly inhibited by drought stress,and cell membrane was also damaged in different degrees.Thus it could be seen that R.latoucheae increased contents of the osmoregulation substances and antioxidant enzyme activities in vivo to adapt to drought stress environment at the same time,making the inhibition and damage degree to the minimum.