【摘要】 贵州高原１４００ｍ的高海拔区．在夏季晴天，烟草叶片没有明显的光合午睡现象。因中午维持高温的时间短，午后降温迅速，中午前后大气相对湿度较高。气温、光合有效辐射及大气ＣＯ２浓度与净光合速率日变化分别呈显著正、正、负相关。这３个生态因子是直接影响光合日变化的主要因子。蒸腾速率、气孔导度、气孔阻力、叶肉阻力及量子效率，与净光合速率日变化分别呈显著正、正、负、负、负相关。高海拔区光合量子效率日变化始终高于中海拔区。在１０３０ｍ的中海拔区，夏季睛天有光合午睡现象，呈不很明显的“一睡不起”型。因中午前后气温高，维持高温时间长，午后降温缓慢；大气相对湿度较低，由早晨至下午１７时，持续下降。试验结果表明，高海拔区烟草较中海拔区具有更加优良的光合生理特性。更多还原

【Abstract】 Leaf photosynthetic characters was measered by using LI～6200 Portable Photosynthetic System in tobacco. At 1,400 m high altitude in Guizhou of China the diurnal variation of net photosynthetic rate (Pn) of tobacco leaves displays nonsignificant by shorttime of high temterature at noon and then it quickly decreased, and this is caused by higher relative air gumidity around noon, too. There are possitive correlation between temperature or photoactive radiation and Pn, nrgative correlation between air CO2 concentration and Pn during day time. Air temperature, photoactive radiation and air CO2concentration are three important ecological direct factors that affect the diurnal variation on Pn. There are possitive correlation between transpiration rate or stomatal conductance and Pn, negative correlation between stomatal resistance or mesophyll resistanc or quantum efficiency and Pn. The diurnal variation of quantum efficiency at highaltitude were higher than that at middle altitude durung day time. At 1030 m middle altitude the diunal changes of Pn showed a one～peak changing pattern and the peak appered at forenoon. This is caused by lunger time of high air temperature around noon and then it slowly decreased, and this is caused by lower relative air humidity, too, and it slowly decreased from 8: 00 am to 17: 00 pm. The results presented that, photosynthetic characters of tobacco at high altitude are better than that at middle altitude.更多还原