Responses Of Leaf Gas Exchange Of Cotinus Coggygria Scop Seedlings Coming From Four Locations In North China To Drought Stress

In order to explore the responses of leaf gas exchange of Cotinus coggygria Scop in different locations of North China to drought stress, studied diurnal change of photosynthetic efficiency parameters, the response characteristics to light intensity and CO2concentration of Cotinus coggygria Scop in four locations, as ShanXi, ShanDong, Western Hills and Yanqing in BeiJing, which under different soil moisture conditions, such as normal supply, mildly drought and severe drought stress. The results showed that:(1) With normal water supply, The photosynthetic capacity of the seedlings coming from Yanqing location was the the strongest.The first peak value of the seedlings coming from Yanqing location was5.50μmolCO2·m-2·s-1,which was1.15,1.44and2.40times of the seedlings coming from ShanXi, ShanDong and XiShan locations respectively. Under drought stress, The peak value of Pn compared later than befor drought stress. And the sensitivity of Pn to drought stress of the seedlings coming from ShanDong location was lower.(2) With normal water supply,the accumulative photosynthetic rate in morning was over60%of the diurnal accumulative photosynthetic rate. The rank of diurnal accumulative photosynthetic rate of seedings coming from four locations was YanQing (136.47±13.30μmolCO2·m-2·s-1)> ShanXi (102.74±14.43μmolCO2·m-2·s-1)> ShanDong (69.80±11.91μmolCO2·m-2·s-1)> XiShan (57.50±10.35μmolCO2·m-2·s-1).The accumulative photosynthetic rate of seedlings coming from YanQing and ShanXi locations were significantly higher than that of XiShan location. Under drought stress, the accumulative photosynthetic rate of the seedings coming from ShanDong and YanQing locations affected on drought stress mildly, and the accumulative photosynthetic rate were higher.(3) With normal water supply, the photosynthetic capacity and adaptability of the seedings coming from YanQing and XiShan locations were stronger. The maximum net photosynthetic rate (Amax) of the seedings coming from YanQing location was20.460±0.72μmolCO2·m-2·s-1, which was1.07,1.17and1.27times of the seedlings coming from ShanXi, ShanDong and XiShan locations respectively. The ranges of the low light of the seedlings coming from ShanXi and YanQing locations were wider. The light compensation point (LCP)of the seedings coming from XiShan location was42.170±5.840μmol-m-2·s-1, which was61.34%,65.33%and87.19%of the seedlings coming from ShanXi, ShanDong and YanQing locations respectively. Under drought stress, the Pn of YanQing location was the highest, but compared with the normal water supply, light response characteristic parameters of the relative value of ShanDong location was best and the drought resistance capacity was the strongest.(4) With normal water supply, ShanXi and YanQing locations of CO2utilization efficiency were higher. The maximum electron transport rate (Jmax) of the seedings coming from ShanXi location was64.05±15.62μmol·m-2·s-1, which was2.10,1.60and1.22times of the seedlings coming from ShanDong XiShan and YanQing locations respectively.But under drought stress, the capacity of fixing CO2of the seedlings coming from ShanDong location affected on drought stress mildly.(5) The sensitivity of Ci, Ls, Gs and WUE to drought stress of the seedlings coming from ShanDong and ShanXi locations were lower than that of other locations.