不同光强下生长的厚叶木莲(Magnolietia pachyphylla)光合作用光响应的变化

VARIATION IN LIGHT RESPONSE OF PHOTOSYNTHESIS IN LEAVES OF MAGNOLIETIA PACHYPHYLLA GROWN ALONG LIGHT GRADIENTS

生长在全光照的厚叶木莲幼树 ,叶片的表观光合量子产率 (αA/molmol-1)为 0 .0 2 46± 0 .0 0 2 3 ,而生长在40 %日光照和 2 0 %日光照的植株 ,αA分别为 0 .0 2 6 6± 0 .0 0 3 1和 0 .0 16 5± 0 .0 0 42 .生长在 40 %日光照的植株叶片光能转换效率 (α /molmol-1)为 0 .2 5 81± 0 .0 0 19,分别较全日光照和 2 0 %日光照高 2 6 .3%和 33.2 % .结果表明 ,40 %日光照有利于厚叶木莲叶片的光能利用和增高光能转换效率 .生长在 2 0 %日光照的植株 ,δ较低 .生长在 40 %日光照的厚叶木莲较生长在全日光照和 2 0 %日光照的有较高的Γ 和Rd.表明厚叶木莲生长在 40 %日光照下能促进光下线粒体呼吸 .而生长在 2 0 %日光照的则有较低的Rd.生长在 40 %日光照的厚叶木莲较生长在全日光照和 2 0 %日光照下的有较高的Vcmax和Jmax.不同光强下生长的厚叶木莲有不同的Jmax和Vcmax比值 ,光强的变化可能改变Vcmax和Jmax的平衡 .40 %日光照有利于增高Jmax.在较高光强的全日光照下生长和在较低光强的 2 0 %日光照下生长的植株 ,气孔对空气CO2 浓度和相对湿度变化的敏感度较生长在 40 %日光照的高 .生长光强改变气孔对一些环境因子的敏感度 .结果表明 ,40 %日光照的环境可能最适应于厚叶木莲异地迁移种植 .图 2表 5参

Apparent photosynthetic quantum yield in leaves of Magnolietia pachyphylla grown at 40% daily light intensity was 0.024 6±0.002 3 mol mol -1 . However, the values of 0.026 6±0.003 1 and 0.016 5±0.004 2 mol mol -1 were found in leaves of saplings grown at full daily light intensity and 20% daily light intensity, respectively. The efficiency of light energy conversion was 0.258 1±0.001 9 mol mol -1 for saplings grown at 40% daily light intensity, 26.3% and 33.2% higher than that of saplings grown at the full daily and at 20% daily light intensities. It may be suggested that light condition with 40% daily light intensity will enhance the efficiency of light energy conversion. On the contrary, the shady condition caused the decrease of light energy conversion. 40% daily light intensity can increase mitochondrial respiration in light and the CO 2 compensation point in the absence of mitochondrial respiration. And higher V cmax and J max were found in leaves of saplings grown at 40% daily light intensity in comparison with those of saplings grown at the full or 20% daily light intensity. Light condition may modify the balance between V cmax and J max . 40% daily light intensity can promote the increase of photosynthetic electron transport rate. And the saplings grown at daily or 20% daily light intensity had higher sensitivity of response to CO 2 concentration and relative humidity in atmosphere in comparison than those of saplings grown at 40% daily light intensity. Light condition under which saplings grow may modify the stomatal response to environmental factors. The environmental condition with 40% daily light intensity may be the best selection for transplantation of Magnolietia pachyphlla . Fig 2, Tab 5, Ref 15