Tognetti Roberto, Michelozzi Marco, Borghetti Marco
Instituto Miglioramento Genetico delle Piante Forestali, CNR, via A. Vannucci 13, 50134-Firenze, Italy.
Tree Physiol. 1994 Jul-Sep;14(7_9):751-758. doi: 10.1093/treephys/14.7-8-9.751.
The morphological and physiological responses (net photosynthesis, stomatal conductance, leaf chlorophyll concentration and leaf orientation) of shade-grown beech seedlings after transfer to a high-light regime were studied in well-watered plants and in plants subjected to water stress. Immediately after exposure to high irradiance, shade-grown seedlings displayed a lower photosynthetic rate, a higher leaf chlorophyll concentration and a more horizontal leaf orientation than light-acclimated plants (control plants). The chlorophyll concentration of shade-grown plants gradually declined throughout the period of exposure to high irradiance reaching the amount observed in control plants. Rates of photosynthesis of shade-grown plants began to recover after 8 days of exposure to high irradiance and recovery was nearly complete after 30 days. Leaf orientation of shade-grown plants also changed rapidly during the first 8 days of exposure to high irradiance and by the end of the experiment, there were no significant differences between shade-grown and control plants. Water stress caused significant declines in net photosynthesis and leaf conductance in both shade-grown and control plants. Net photosynthesis did not recover completely in the shade-grown water-stressed plants during the 30-day exposure to high irradiance. Reversible leaf paraheliotropism and chlorophyll bleaching were observed in response to soil drying followed by rewatering.
研究了在水分充足的植株以及遭受水分胁迫的植株中，遮荫生长的山毛榉幼苗转移至高光照条件后其形态和生理响应（净光合速率、气孔导度、叶片叶绿素浓度和叶片方向）。刚暴露于高光照强度后，与适应光照的植株（对照植株）相比，遮荫生长的幼苗光合速率较低、叶片叶绿素浓度较高且叶片方向更水平。在整个暴露于高光照强度的期间，遮荫生长植株的叶绿素浓度逐渐下降，降至对照植株中观察到的水平。遮荫生长植株的光合速率在暴露于高光照强度8天后开始恢复，30天后恢复基本完成。在暴露于高光照强度的前8天，遮荫生长植株的叶片方向也迅速改变，到实验结束时，遮荫生长植株和对照植株之间没有显著差异。水分胁迫导致遮荫生长植株和对照植株的净光合速率和叶片导度显著下降。在暴露于高光照强度的30天期间，遮荫生长且遭受水分胁迫的植株的净光合速率没有完全恢复。观察到因土壤干燥随后再浇水而出现的可逆性叶片避日性和叶绿素漂白现象。
