桂花夏季光合特性及其与环境因子的关系

Photosynthetic Characteristics of Osmanthus fragrans Leaves and its Relation to Environmental Factors in Summer

对盆栽5a生丹桂的研究结果表明:净光合速率日变化曲线为"双峰"型,光合效率午间明显降低,主要由非气孔限制引起。表观量子效率和实际光化学效率的降低是非气孔限制形成和发展的深层原因。蒸腾速率的日变化为"单峰型",午间最高。利用多元逐步回归方法得到净光合速率和蒸腾速率与环境因子的最优方程,气温和光合有效辐射对净光合速率和蒸腾速率的影响较大。夏季适当遮荫有利于丹桂降低光抑制,提高净光合速率,促进植株生长。

Mature leaves of 5-year-old potted Osmanthus fragrans var. aurantiacus Mak. were used to determine photosynthesis. The results were as follows. In summer clear days, the curve of diurnal variations of net photosynthetic rate （Pn） had two peaks, which had an obvious phenomenon of midday decline of photosynthetic efficiency. The mid-depress of Pn was principally caused by non-stomatal limited elements. The decrease of apparent quantum yield （AQY） and actual photochemical efficiency at noon showed that there existed photoinhibition, which was the intrinsic reason why nonstomatal limitation could form and develop. The curve of diurnal variation of transpiration rate （Tr） had one peak exhibiting highest value at noon. The most excellent equation of the diurnal variation of Pn and Tr was attained by the method of stepwise multi-regression. The analysis of partial correlation and path coefficient on Pn, Tr and factors showed that the diurnal variation of Pn and Tr had closer relations to photosynthetic active radiation （PAR）, air relative humidity （RH）, and air temperature （Ta）. PAR, RH and T. were the primary direct factors which effected Pn and Tr. The order of effected ability on Pn and Tr were Tn〉PAR〉RH. It is suggested that mild shading culture of Osrnanthus fragrans var. aurantiacus Mak. is beneficial to the reduction of leaf temperature and photoinhibition in summer.