自然条件下植物叶片CO2同化率昼夜变化的生理生态特性

本文利用二氧化碳分析仪及开放式叶室，分别于旱、温季节在野外观测１３种乔木树种的叶片ＣＯ２同化速率的全天变化，分析各种植物白天净光合速率曲线类型的特点和夜间呼吸与气温的回归关系．结果：７月份植物白天光合时间相对较长，中午，植物光合曲线的午休现象表现不一，曲线特征取决于种的生物特性及环境因子．在气温较高的范围内（２５～３０℃）夜间阔叶树种的呼吸与气温呈负相关，但在１月份却不明显，针叶树种的夜间呼吸无论在高温、潮湿的７月份还是低温、干旱的１月份都不与温度呈现线性关系．

DIURNAL VARIATION IN NET PHOTOSYNTHETIC RATE AND RESPIRATION RATE OF PLANT LEAF UNDER NATURAL CONDITIONS

Diurnal CO2 assimilation of 13 tree species was measured in natural environment by means of CO2assimilation analyzer with open leaf chamber system. The measurements were undertaken selectively in January(with low air temperature and low humidity)and July(with high air temperature and high humidity).Due tothe characteristies of biological structure and environmental factors, plant leaf exhibited different responsepatterns of CO2 assimilation. In July the plants had higher mean net photosynthetic rates and longer durationof photosynthesis than in January. Midday depression of net photosynthetic rate at noon differred greatlywith different species and at different seasons. The photosynthetic rates in some species were depressed veryclearly at noon,but some slightly and some very slightly. Native broadleaved trees displayed a one-peak pattern in January. Regression analysis showed that the respiration of broadleaved species was correlated negatively with air temperature in a narrow temperature range at night in July. In January no obvious correlativerelationship was found. Coniferous trees,in contrast,did not display such linear relation, but always kept lowrespiration both in January and July.