Effects Of Light Intensity And Temperature On Photosynthesis Of Syntrichia Caninervis

Syntrichia caninervis, the dominant species of moss crusts grown in Southern Gu Er Ban Tong Gu Te desert in its north was studied in this paper. Li-6400 portable photosynthesis device was used to measure the photosynthetic parameters change law of moss crusts rehydration and dehydration under different light intensity and temperatures. Control different photosynthetic available radiation through red and blue light leaf chamber of photosynthesis system to understand the influence mechanism of the influence of light intensity on photosytnesis in the process of rehydration-dehydration. Control different test temperature through temperature control device to discuss the effect of temperature change on photosynthetic rate change in the process of rehydration-dehydration. Using path analysis to determine the factors that affect the photosynthetic rate change in the process of rehydration-dehydration. This test can provide based data for photosynthesis change rule of desert moss crusts. The exploration of the drought mechanism under effect of different environmental factors can provide important theoretical supports for restoring desert ecosystem.The main research results:1.Moss crusts recovered metabolism quickly after getting moisture during dormant period, photosynthesis rate entered dormant state from negative straightly up to the maximum then rapidly dropped to near zero; Transpiration rate kept high value after rehydration and rapidly dropped to near zero after a period of time. Water use efficiency started to decline from negative up to the first maximum after rehydration, then kept rising to the second peak during a period of time, meanwhile, the second peak greater than the first peak.2.In the process of rehydration-dehydration, light intensity significantly affected photosynthesis of moss crusts. The started carbon sequestration time shortened with the increase of light intensity. Maximum net photosynthetic rate increased significantly with the increase of light intensity; Duration of rehydration-dehydration shortened with the increase of light intensity; Transpiration rate and water use efficiency raised with the increase of light intensity.3. In the process of rehydration-dehydration, temperature significantly affected the change of photosynthetic rate. The higher the temperature, the shorter the moss crusts start carbon sequestration; the greater the net photosynthetic rate, the shorter the duration of photosynthesis. Transpiration rate increased with the rise of temperature.4. In the process of rehydration-dehydration, the relative water content in moss crusts declined straightly, the greater the light intensity, the faster the water dropped. At the temperature of 25℃,20℃,10℃, the most suitable relative water content of moss crusts photosynthesis were 5%—47%,15%—45%,25%—35%.5. Among different photosynthesis-light response curves under different temperatures, moss crusts can make better use of weak light with the increase of temperature, and not easy to appear photoinhibition under strong light irradiation.6. In the process of rehydration-dehydration, net photosynthetic rate had a great relevance with temperature and relative water content, however, leaf temperature, air humidity, photosynthetic available radiation and the relative water content were the indirect influence on net photosynthetic rate. Key words: moss crust, photosynthesis, rehydration-dehydration, light intensity, temperature...