Effects of soil moisture on photosynthetic characteristics of Zaosu pear during fruit expanding period

Under controlled soil moisture conditions,the photosynthetic characteristics of Zaosu pear during fruit expanding period were measured.It was found that the net photosynthetic rate(Pn) under the treatments of W1,W2 and W3(denoted soil water at 40±5%,60±5% and 80±5% of field capacity,respectively) appeared the first peak at 10 o′clock,being 18.14 μmol·m-2·s-1,19.43 μmol·m-2·s-1 and 20.25 μmol·m-2·s-1 respectively,and appeared the second peak at 16 o'clock,being 14.96 μmol·m-2·s-1,16.47 μmol·m-2·s-1 and 17.32 μmol·m-2·s-1 respectively.The time of Pn value being more than 12.00 μmol·m-2·s-1 in the whole day under W1,W2 and W3 was 5,7 and 9 hours respectively.The light compensation point(LCP) of W2 and W3 was significantly lower than that of W1,but the light saturation point(LSP) of W2 and W3 were significantly higher than that of W1.There were no significant difference of maximum photosynthetic rate(Pmax) between W1 and W2,both being significantly lower than W3.The CO2 compensation point of W2 was significantly lower than that of W1,but there was no remarkable difference between W2 and W3.The CO2 saturation point of W2 was the highest,while that of W3 was the lowest.At CO2 saturation point,the Pmax of W2 was significantly higher than that of W1,but there was no remarkable difference between W2 and W3.