风力胁迫对具鞘微鞘藻结皮光合活性的影响

EFFECT OF WIND STRESS ON PHOTOSYNTHETIC ACTIVITY OF MICROCOLEUS VAGINATUS CRUSTS

抵抗风力胁迫是荒漠藻类适应干旱区环境的重要生物学机制,也是藻结皮能够拓殖流沙的必要条件之一,但有关藻类对风力胁迫的响应机理国内外尚无研究报道。以具鞘微鞘藻(Microcoleus vaginatus Gom.)人工结皮为实验对象,研究了不同强度风力吹蚀对结皮含水量、藻类活力、生物量、及其光合活性的影响。结果表明:不论低于当地起沙风(3m/s)还是高于起沙风(5m/s和7m/s)的风力吹蚀,结皮中藻类生物量均明显下降,而且结皮生物量的变化与风速大小和吹蚀时间呈线性关系(y=14.78+0.035a-1.48b,a风速,b时间,r2=0.79)。进一步分析发现,风力吹蚀后结皮中藻类活力并没有降低但主要光合色素和天线色素的含量普遍降低,叶绿素荧光(Fv/Fm)、表观电子传递速率(ETR)和净光合速率(Pn)明显下降,并且风速越大,降幅越大。这些结果说明风力胁迫对藻结皮生长和光合活性的影响主要是通过影响光合色素代谢合成和电子传递速率引起的,对其生命力没有明显影响。

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. Accord-ingly 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, r^2=0.79）. After 7 hours continuous blowing at different scales wind forces, the main photosynthetic pigments and antenna pig- ments 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 elec-tron transport rate, but algal cell vitality was not affected obviously.