【摘要】 研究采用目前先进的光合作用测定系统L i-Cor-6400测定濒危物种西藏巨柏的光合作用,自然环境条件下的西藏巨柏光合日进程表现为单峰型曲线,在12:00时左右达到最高峰,其光合作用不存在“午休现象”。在12:00时,西藏巨柏的气孔限制值和水分饱和亏缺分别达到最大值,此时的水分利用效率较高,在9:00时,西藏巨柏获得一天中最大的表观量子效率,水分利用效率达到最大值。其蒸腾速率在13:00时最大,这个时间并不与光合速率最大值同步,这说明在西藏特殊的气候环境条件下,影响光合速率的因素很多。在光合速率的日进程中,高光合速率值(大于4.00μm o lCO2/(m2.s))持续时间在5h左右,这使得西藏巨柏的光合作用产物得以有效积累,也为西藏巨柏在半干旱环境中的生长创造了有利条件。更多还原

【Abstract】 The photosynthesis of the endangered species,Tibetan Cupressus gigantea,was analyzed with Li-6400.The curve representing the diurnal course of the photosynthetic rate of Tibetan Cupressus gigantea has a single peak,at which the photosynthetic rate reaches the maximum value at 12:00.And this indicates that there existed no "midday depression" in the photosynthesis of Tibetan Cupressus gigantea.The stomatal limitation and water pressure saturation deficits of leaf also reached maximum values at 12:00 AM and at this moment the water utilization efficiency was still high,but it was lower than the highest water utilization efficiency at 9:00 in the morning.At 9:00,the apparent quantum yield of Tibetan Cupressus gigantea also reached the maximum value in a day.The transpiration rate had the maximum value at 13:00,which was not in parallel with the photosynthetic rate in time.In the diurnal variation of photosynthetic rate,the photosynthetic rate maintained at a relatively high level（more than 4.00μmolCO₂/（m²·s）） for about 5 hours.This increased the overall production of photosynthates in daily course and was advantageous to the growth of Tibetan Cupressus gigantea in the semi-drought environment in Tibet.更多还原