荒漠区盐生草种子萌发和幼苗生理生态特征对环境因子响应机制研究

Xeromorphic annual forb Halogeton glomeratus (Bieb.) C. A. Mey. distributes spontaneously in an extreme harsh desert environment, which characterized by high temperature, high level of salinity and extreme aridity. Accordingly, H. glomeratus had formed an ability to adapt to harsh desert environments. H. glomeratus often forms a momodominant synusia in desert environments, thus, plays an important role in windbreak, sand fixation and water-soil conservation. Thereby H. glomeratus could be taken into account as a pioneer plant for desert ecosystem revegetation. However, the ecophysiological adaptation mechanism of H. glomeratus to extreme harsh desert environment hardly had been reported. This project examined the effects of temperature, light, salinity, soil water content and seed burial depth single or multiple on the germination of H. glomeratus. As a results the threshold of environmental factors appropriate for germination of H. glomeratus could be quantified, meanwhile the germination adaptation mechanism of H. glomeratus to desert environment could be detected. This project also studied the effects of aridity, high temperature, enhanced UV-B radiation and salinity single or multiple on water characteristics, photosynthetic characteristics, reactive oxygen species contents, malondialdehyde contents, protective enzyme activities, osmotic adjustment substances contents and ion distribution characteristics (under salt stress) of H. glomeratus seedlings. Thus, the responses mechanism and adaptation mechanism of H. glomeratus seedlings adapt to extreme harsh desert environment could be discovered. Results from this project not only supply the scientific information for desert ecosystem revegetation and reconstruction, but also play an important role in enriching the physiological- and ecological- theoretics study of desert plant stress resistance mechanism.

盐生草是在气候极端干旱、高温和土壤盐渍化严重等严酷环境下出现的一种旱中生一年生草本，具有适应荒漠极端环境的能力，在荒漠中常形成层片，对于防风固沙、水土保持等具有重要意义，适宜作荒漠生态系统植被修复的先锋植物。然而，盐生草应对荒漠极端环境的生理生态适应机制尚不清楚。本项目以盐生草为研究对象，分析温度、光照、盐分、土壤水分和沙埋厚度单因素和复合对盐生草种子萌发特性的影响，量化适宜盐生草种子萌发的环境因子阈值，揭示盐生草种子萌发对荒漠环境的适应对策；研究干旱、高温、增强UV-B辐射和盐分单因素和复合对幼苗水分特征、光合特征、活性氧含量、丙二醛含量、保护酶活性、渗透调节物质含量以及盐胁迫下离子分布特征的影响，揭示盐生草对荒漠极端环境的响应及适应机制。本项研究不仅可为荒漠生态系统植被修复和重建提供科学依据，而且其成果对于丰富荒漠植物逆境生理生态学理论具有重要的科学意义。

盐生草是在气候极端干旱、高温和土壤盐渍化严重等严酷环境下出现的一种旱中生一年生草本，具有适应荒漠极端环境的能力，在荒漠中常形成层片，对于防风固沙、水土保持等具有重要意义，适宜作荒漠生态系统植被修复的先锋植物。然而，盐生草应对荒漠极端环境的生理生态适应机制尚不清楚。本项目以盐生草为研究对象，分析温度、光照、盐分、土壤水分和沙埋厚度单因素和复合对盐生草种子萌发特性的影响，量化适宜盐生草种子萌发的环境因子阈值，揭示盐生草种子萌发对荒漠环境的适应对策；研究干旱、高温、增强UV-B辐射和盐分对幼苗水分特征、光合特征、活性氧含量、丙二醛含量、保护酶活性、渗透调节物质含量以及盐胁迫下离子分布特征的影响，揭示盐生草对荒漠极端环境的响应及适应机制。本项研究不仅可为荒漠生态系统植被修复和重建提供科学依据，而且其成果对于丰富荒漠植物逆境生理生态学理论具有重要的科学意义。研究表明，盐生草种子分别在光照和黑暗5-40°C的恒温条件下都保持较高的萌发率，大于70%。盐生草种子在大于0.4 mol/L NaCl处理下萌发受抑制，当NaCl处理浓度大于1.0 mol/L时，种子停止萌发，但将种子转移至蒸馏水后，种子的萌发恢复率很高，大于85%。降雨充分条件下，盐生草种子在裸露、沙埋5和10 mm条件下，都能够很好的出苗，沙埋20 mm情况下种子出苗较低，而沙埋30 mm的情况下，无种子出苗。在UV-B辐射和盐分胁迫下盐生草Pn下降主要是由非气孔限制所致。干旱和高温胁迫下盐生草Pn下降的限制因子是气孔限制。盐生草在干旱、高温、增强UV-B辐射和盐分等胁迫下，都会导致体内H2O2和MDA含量增加。环境因子胁迫下盐生草SOD和APX活性较对照均有所提高，说明盐生草抗氧化酶系统做出相应反应。干旱和高温胁迫下，脯氨酸和可溶性糖起着重要的渗透调节作用。盐胁迫下盐生草主要以无机离子Na+而并非有机渗透调节物质作为主要渗透调节剂。具有肉质化叶的盐生草叶片对Na+和Cl–的积累量远高于茎和根部，主要起到渗透调节和维持叶组织水分含量等作用。