土壤水分胁迫对杜仲叶片光合及水分利用特征的影响

Effect of Soil Water Stress on Photosynthetic and Transpiration Characters of Eucommia ulmoides

通过实验研究了华北石质山区4种不同土壤水分条件下3a生杜仲苗木叶片光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、胞间CO2浓度(Ci)、气孔限制值(Ls)、水分利用效率(WUE)等参数的光响应过程。结果表明:(1)杜仲叶片在土壤水分轻度(W1)、中度(W2)和重度(W3)胁迫条件下的光饱和点分别比对照(CK)下降12.5%、44.8%、68.5%,晴天日光合速率最大值分别比对照(CK)下降21.5%、47%、69.7%;(2)叶片蒸腾速率(Tr)呈现随光合有效辐射(PAR)增加而上升的趋势。对比CK,Tr在W1、W2和W3条件下分别下降了17%、52%和93%;(3)Gs随着PAR的增加而逐渐上升。对比CK,Gs在W1、W2和W3条件下分别下降了22.6%、67.9%、88.7%。从无水分胁迫一直到中度水分胁迫条件下,气孔限制是影响光合作用的主要原因,而土壤水分严重胁迫条件下,当PAR小于1000μmol.m-2.s-1时,气孔限制是影响光合作用的主要原因,尔后转变为非气孔限制;(4)叶片水分利用效率(WUE)对光强的适应范围比较广,W3条件下,WUE值最高。CK、W1、W2条件下,WUE相差不大,对比W3,分别下降68.6%、69.5%、67.3%。

In this study, observation by Li-6400 system was used to analyze the light response of some physiological fac- tors, such as net photosynthetic rate （Pn） , transpiration rate （Tr） , stomatal conductance （Gs） , intercellular CO2 （Ci） , stomatal limitation value （Ls） and water use efficiency （WUE） of 3-years-old Eucommia ulmoides ,which was planted in the rocky mountain of North China under different soil water stress. Soil water was engaged in four levels of about 75% （CK） ,55% （W~） ,40% （W2 ） and 30% （ W3 ） of soil water holding capacity. The results showed that： （ 1 ） Light satura- tion point for W~ ,W2 and W3 of Eucommia ulmoides was 12. 5% ,44. 8% ,68.5% lower than CK respectively. The maxi- mum net photosynthetic rate on sunny day reached crest under the condition of CK, which was 21.5% , 47% and 69. 7% higher than W~ ,W2 ,W3 respectively; （2） The transpiration rate （Tr） increased with the rise of photosynthetic active radia- tion （PAR）. Compared with CK, Tr was 17%, 52% and 93% lower under Wl , W2 and W3 ; （3） Gs increased with the rise of PAR. Compared with CK, Gs decreased by 22.6% , 67.9% , 88.7% under W1 , W2 and W3. Without water stress or with mild water stress, stomatal limitation was the main factor to influence photosynthesis. But under severe stress conditions, when the PAR came to 10001.Lmol m-2s-1, the main reason for impact of photosynthesis changed from stomatal limita- tion to non-stomatal limitation; （4） Water use efficiency （WUE） reached highest under W3 condition. There was little vari- ation under CK, Wl , W2. However, compared with W3 , WUE decreased by 68. 6%, 69. 5%, 67. 3%.