Characteristics of Photosynthesis and Water Physio-ecology of Young Macrocarpium officinalis

On the conditions of 20 ℃,the various intensities of photosynthesis active radiation (PAR) and different CO2 concentrations(),the characteristics of leaf photosynthesis and water physio-ecology of young Macrocarpium officinalis on the convering tree land from farming were studied. The results showed that:(1)under 400 μmol·mol-1·s-1,the regression equation between net photosynthesis rate (Pn) and PAR is Pn=-8×10-6PAR2+0.022 2PAR+1.950 9 with a regression coefficient(r)=0.952 4(n=33); the critical points of light saturation and light compensation,apparent quantum yield (AQY) is 1 387.5 μmol·m-2·s-1 and 17.4 μmol·m-2·s-1,0.066 3 mol·mol-1 respectively.The regressive equation between transpiration (Tr) and PAR is Tr=0.001 3 PAR+5.637 with r= 0.983 0(n=33).The relationship between water utilization efficiency (WUE) and PAR showed parachute trends with r=0.922 2(n=33).(2)At 1 200 μmol·m-2·s-1 PAR,the regressive equation between Pn and is Pn=-2×10-52+0.050 2-2.965 6 and r is close to 1.0(n=33).CO2 saturation point,compensation point and carboxylation efficiency is 1 255 μmol·m-2·s-1,60.5 μmol·m-2·s-1,and 0.040 6 respectively;Tr showed linely down trend with decreasing,but there was no significant correlation between them,the regressive equation between WUE and is WUE=-4×10-62+0.008 4-5.505 2 and r is close to 1.0(n=30).