Daily and seasonal variation of photosynthetic characteristics of Carex leucochlora

Daily variation of photosynthetic characteristics and light-photosynthetic rate response curve of Carex leucochlora were analyzed using Licor-6400 portable photosynthesis system in May, August and October. The results showed that the daily variation of net photosynthetic rate, transpiration rate and stomatal conductance in leaves presented two-peak curve and midday depression in May and presented single-peak curve in both August and October. Photosynthetic characteristics were extensively affected by environmental conditions of different months. The maximal net photosynthetic rate had closer correlation with soil moisture and air temperature. The lower transpiration rate and stomatal conductance and higher water utilization efficiency indicated that C.leucochlora was a drought-resistant plant species. Net photosynthetic rate of C.leucochlora was low in different months. Light compensation points were less than 20 μmol·m-2·s-1, light saturation points were less than 1 000 μmol·m-2·s-1 in May and August. Light compensation points were 30 μmol·m-2·s-1 and light saturation points were 1 047 μmol·m-2·s-1 in October which indicated that C.leucochlora was a typical shade-tolerance plant.