沼泽、盐化沙丘过渡带和沙丘生境下芦苇的光合及生理生化特性

对于田地区3种不同生境(沼泽、盐化沙丘过渡带和沙丘顶)芦苇的生长环境特征、光合特性、渗透调节及抗氧化系统的特征进行研究。结果表明:芦苇叶片的Pn日变化在沼泽生境呈单峰曲线,在盐化沙丘过渡带和沙丘顶部均为双峰曲线,光合"午休"现象明显,气孔导度降低是其主要原因。脯氨酸和可溶性糖含量随根区土壤水分减少和盐分加剧增加显著,其中可溶性糖含量变化剧烈,对抵御干旱和盐渍化危害的贡献较大。芦苇叶片超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性随干旱及盐分加剧增加显著,两者对水分亏缺的响应较盐分敏感,且可有效缓解沙丘生境由于缺水所造成的氧化损伤,使丙二醛(MDA)含量维持在相对较低水平。过氧化物酶(POD)活性在沙丘和盐渍化生境内都比较高,对抵抗盐渍化和干旱起着同样重要的作用。

Photosynthesis and physiological-biochemical characteristics of Phragmites australis in swamp, light salt meadow, and sand dune habitats

The aim of present study was to investigate the adaptability of Phragmites australis (common reed) under three different water and salt levels in the field. Environmental factors, photosynthetic parameters, osmotic adjustment substances, and antioxidant enzymes were determined in P. australis, which were grown in swamp, light salt meadow, and dune habitats. P. australis grown in light salt meadow and dune habitats showed two peaks of diurnal variation of P_n, which indicated a remarked photosynthetic "midday depression", while there was one peak in swamp reed. The midday depression of photosynthesis was intrinsically caused by the reduction of stomatal conductance. As critical indices of resistance to drought and salinization, proline and soluble sugar content in P. australis leaves increased significantly with the intensification of drought and salt, and soluble sugar was more important for the resistance to drought and salinization. Superoxide dismutase (SOD) and catalase (CAT) activities in P. australis leaves increased significantly when there was less water and more salt in the root region. The responses of SOD and CAT to water deficiency were more sensitive than to salinity, and could effectively resolve oxidative damage induced by the water deficit. The peroxidase (POD) activities were high in both the dune and saline habitat, indicating that POD plays a major role in resistance to water deficit and salinity in oxidative defense systems of P. australis. The malondialdehyde (MDA) content was the lowest in swamp reed, and highest in light salt meadow reed.