不同郁闭度条件下野生黄连木幼苗的光合及水分利用特征

Photosynthesis and Water Use Characteristics of Pistacia chinensis Under Different Coverage Conditions

研究了华北石质山区不同郁闭度条件下野生黄连木5年生幼苗叶片的净光合速率、蒸腾速率、气孔导度、胞间CO2摩尔分数、气孔限制值、水分利用效率的光响应和CO2响应特征。结果表明:①幼苗叶片在不同郁闭度下的光响应过程基本相似,净光合速率都随着光合有效辐射强度的升高而增加,到达光饱和点后逐渐平缓。郁闭度0条件下,黄连木有较高的光饱和点,对高光条件具有较强的适应性。②幼苗叶片的蒸腾速率都随着光合有效辐射的增加而逐渐上升,在光合有效辐射为0～1 400μmol.m-2.s-1范围内,郁闭度为0.4、0.8条件下的蒸腾速率平均值比郁闭度0时分别降低了24%、55%,高郁闭度对黄连木幼苗蒸腾强度具有明显的抑制作用。③郁闭度为0、0.4时,黄连木幼苗对空气CO2摩尔分数的响应明显,而且响应特征明显有别于郁闭度0.8的,遮光严重时黄连木对CO2摩尔分数的响应敏感程度下降。④高郁闭度条件下,当光合有效辐射小于1 200μmol.m-2.s-1时,气孔限制是影响光合作用的主要原因,而后转变为非气孔限制;低郁闭度条件下,气孔导度不是制约黄连木幼苗光合的主要因素,非气孔限制是影响黄连木幼苗高光合作用的主要原因。⑤不同郁闭度下,当光合有效辐射小于200μmol.m-2.s-1时,水分利用效率随着光合有效辐射增加而迅速增加,其后在较高水平上基本保持不变,黄连木是一种干旱适应性较强的树种。

Light response and carbon dioxide response characteristics of net photosynthetic rate,transpiration rate,stomatal conductance,intercellular carbon dioxide concentration,stomatal limitation value and water use efficiency of leaves of 5-year-old wild Pistacia chinensis at different crown densities were observed in the rocky mountainous area of north China.Results showed that,at different crown densities,the seedlings were similar to each other in response to light,and net photosynthetic rate increased with increasing photosynthetic active radiation and gradually tended to be steady after reaching the light saturation point.When the crown density was zero,the seedlings had higher light saturation points,indicating that P.chinensis seedlings have a good adaptability to strong light.Transpiration rate of the seedlings increased with increasing photosynthetic active radiation.When the photosynthetic active radiation ranged from 0 to 140μmol·m-2·s-1,compared with the transpiration rate for the crown density of zero,the transpiration rates for crown density of 0.4 and 0.8 decreased by 24 percent and 55 percent,respectively.High crown density had an obvious inhibitory effect on transpiration of the seedlings.When crown density was zero or 0.4,the seedlings showed obvious responses to carbon dioxide concentration,and the response feature was different from that of crown density of 0.8.The seedlings at high crown density exhibited a declined sensitive degree to carbon dioxide concentration.At high crown densities,when the photosynthetic active radiation was less than 1200μmol·m-2·s-1,the main influence factor on photosynthesis changed from stomatal limitation to non-stomatal limitation;at low crown density of 0 or 0.4,non-stomatal limitation was the main influence factor on photosynthesis.At different crown densities,water use efficiency of the seedlings increased rapidly with increasing photosynthetic active radiation when photosynthetic active radiation was less than 200μmol·m-2·s-1,and then kept at a fairly high level.Pistacia chinensis has strong adaptability to arid environment.