EFFECT OF WIND STRESS ON PHOTOSYNTHETIC ACTIVITY OF MICROCOLEUS VAGINATUS CRUSTS

Algal crusts are the early stage of biological soil crusts development and succession in the arid and semi-arid regions, in which filamentous cyanobacteria are often dominant organisms, and these algae have been recognized to possess importance functions both in the stabilization of topsoil, retarding water evaporation, meliorating soil structure, and enhancing soil fertility. Of course, the environments they grow and survive determine that they are often subjected to harsh environmental conditions, such as windy, arid, sunny irradiation and extreme temperature fluctuation. Accordingly these organisms have developed variable strategies to adapt them. Up to data, their adaptation to drought, radiation and salt stress have been studied extensively, but few is done for wind force stress, and very little is known about its acclimation to this stress. Microcoleus vaginatus is the first dominant species and community- building species of more than 95% algal crusts on the world, with the most promising foreground in desertification control and application of algal crusts. The objective of this study is to explore the effects of wind stress on photosynthetic activity of M.vaginatus crusts. In this study, M. vaginatus isolated from Qubqi Desert was batch cultured, and inoculated onto the surface of local shifting sand in laboratory. After the algal crusts formation, they were taken to the outdoors for stress exercise for 10 days from 9:00 to 12:00 everyday. Then the man-made M.vaginatus crusts were exposed to different scales wind forces environments (3m/s, 5m/s and 7m/s), algal physiological responses were in situ studied. The results showed that alga biomass decreased significantly under windy conditions, it was significantly negatively correlated with blowing time, but positively correlated with wind force scale (y = 14.78 ? 1.48a + 0.035b, a blowing time, b wind force, r2=0.79). After 7 hours continuous blowing at different scales wind forces, the main photosynthetic pigments and antenna pigments contents, chlorophyll fluorescence (Fv / Fm), the apparent electron transfer rate (ETR) and net photosynthetic rate (Pn) decreased significantly, and the greater drop occurred at the stronger wind force. Above results indicated that wind force stressed algal growth and photosynthetic activity by impacting metabolism of pigments and photosynthetic electron transport rate, but algal cell vitality was not affected obviously.