Photosynthetic characteristics of 4 wild plants in Yintan wetland in Lanzhou section of Yellow River

The present study analyzed the relationship between photosynthetic characteristics in different growth stages and environmental factors and discussed plant adaption characteristics and mechanism in wetlands based on natural plants of Lythrum salicaria, Phragmites australis, Scirpus triqueter and Acorus calamus’s growing in Yintan wetland of Lanzhou section of Yellow River. In May 11, the two peaks curve of net photosynthetic rate (Pn) of L. salicaria and P. australis was not obvious and the Pn of S. triqueter and A. calamus were relatively stable, the average of Pn decreased in the following order: P. australis>L. salicaria>S. triqueter>A. calamus. In August 19, the curves of Pn of L. salicaria, P. australis and S. triqueter showed two peaks with significant photosynthetic “midday depression” and the curves of Pn of A. calamus was one peak, the average of Pn decreased in the following order: P. australis>A. calamus>L. salicaria>S. triqueter. In May 11, photosynthetically active radiation (PAR), atmospheric temperature (Ta), atmospheric CO2 concentration (Ca), relative humidity (RH), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and water use efficiency (WUE) had positive correlation or significant correlation with the diurnal variation of Pn. In August 19, only PAR, Ca, Tr, Gs, WUE and soil moisture had positive correlation or significant correlation with the diurnal variation of Pn. In May 11, PAR and WUE had the greatest effects on Pn of 4 studied plants, which were the major environmental and physiological factors. In August 19, PAR and Tr had the greatest effect on Pn of L. salicaria and S. triqueter’s and PAR and WUE had the greatest effect on Pn of P. australis and A. calamus which were the major environmental and physiological factors. Although each factors had different effects, PAR was the main cause of plant photosynthetic physiological characteristics.