微鞘藻胞外多糖在沙漠土壤成土中的作用

THE FUNCTION OF EXOPOLYSACCHARIDES OF MICROCOLEUS IN THE FORMATION OF DESERT SOIL

研究了沙坡头藻结皮中的优势物种——微鞘藻的胞外多糖对沙漠表层土壤水分分布状况的影响及其光合特性。随着胞外多糖浓度的升高 ,土壤持水量增大 ,土壤水分蒸发速率降低 ,水分在土壤中运动的速率被延缓。藻总水溶性多糖产率为 2 8.82 % ,胞外水溶性多糖产率为 1 6 .0 9% ;多糖产量在稳定期生物量最大时增长最快。微鞘藻光合作用最适温度为 2 5℃ ,最适光强为 40 0 μE.m- 2 .s- 1,在 0 .3 mol/ L Na Cl浓度下其光合作用活性被强烈抑制 ;微鞘藻的吸收光谱表明它比生长在湿润地区的藻类含有更多的胡萝卜素成分 ;叶绿素 a荧光 (Fv/ Fm)分析表明在失水约为初始湿重的 5 6 %时 Fv/ Fm值恢复到水培养的 96 % ;其光合作用特性有利于对逆境的适应和生物量的积累。表明微鞘藻胞外多糖可影响沙漠表层土壤水分分布状况 ,并可作为一种潜在的生物肥料 ,在荒漠原始成土过程中扮演着重要角色。

The present work deals with the exopolysaccharides (EPS) and photosynthetic activities of Microcoleus vaginatus (one of the pioneer species in algal crusts at Shapotou, Linxia) With the concentration of EPS increasing, water holding capacity of desert soil was increasing,water evaporation was decreasing,and water movement through the desert soil was retarded The yield of exopolysaccharides was 28 82% of dry weight, and reached the maximum during the stationary phase Microcoleus had more carotenoid contents than other misted cells in view of its absorption spectrum;the most optimum temperature for photosynthesis was about 25℃, the most optimum light intensity for photosynthesis was 400μ Em -2 s -1 , and photosynthetic activity was inhibited strongly after 0 3mol/l of NaCl; the value of Chlorophyll a fluorescence(Fv/Fm) recovered 96% of cultures after losing water to 56% of fresh weight It indicated that Microcoleus influenced the hydrological properties and played an important role in desert soil formation