Dynamic response of stomata to changing irradiance in loblolly pine (Pinus taeda L.).
Dynamic response of stomata to changing irradiance in loblolly pine (Pinus taeda L.).
复制标题
火炬松气孔对光照变化的动态响应。
作者：
D. Whitehead;R. Teskey
以火炬松（Pinustaeda L.）针叶为材料，研究了光照强度从800 μ mol·m ~（-2）·s ~（-1）降低到200 μ mol·m ~（-2）·s ~（-1）的遮荫处理对针叶气孔导度和光合速率的影响。实验室条件下的树木遮荫诱导气孔导度下降39%，但变化速度缓慢。平均时间常数（+/-标准误差）较短的气孔导度下降时，遮光施加30分钟（14.8 +/- 1.3分钟）比气孔导度增加时，遮光去除（25.5 +/- 3.4分钟）。遮光解除后气孔导度增加的时间常数与前一黑暗期的长短呈线性关系。光合速率下降58%，立即施加遮荫时，增加更迅速比气孔导度的变化时，遮荫解除。遮光解除后，诱导期光合作用的增加受到气孔和生化效应的限制。气孔响应的时间常数长，气孔导度和瞬时测量的辐照度从现场数据之间的相关性差。然而，气孔导度对光照变化的缓慢响应对日蒸腾总量、碳增益和水分利用效率的影响不大。
Dynamic changes in stomatal conductance and the rate of photosynthesis were measured as periods of shading (decrease in irradiance from 800 to 200 micro mol m(-2) s(-1)) between 5 and 60 min were imposed on needles of Pinus taeda L. trees under laboratory conditions. Shading induced a 39% decrease in stomatal conductance but the rate of change was slow. Average time constants (+/- standard error) were shorter for the decrease in stomatal conductance when shading was imposed for 30 min (14.8 +/- 1.3 min) than for the increase in stomatal conductance when shading was removed (25.5 +/- 3.4 min). The time constants for increasing stomatal conductance when shading was removed were linearly related to the length of the previous dark period. The rate of photosynthesis fell immediately by 58% when shading was imposed and increased more rapidly than the change in stomatal conductance when shading was removed. The increase in photosynthesis during the induction phase after shading was removed was limited by both stomatal and biochemical effects. The long time constants for stomatal response contributed to the poor correlations between stomatal conductance and instantaneous measurements of irradiance from field data. However, the slow response of stomatal conductance to changes in irradiance had little effect on total daily transpiration, carbon gain and water-use efficiency.