不同生育期滇重楼光合日变化及光响应特征1）

于2013年6月（花期）、8月（果实膨大期）和9月（果实成熟期）份对3年生幼龄期滇重楼和8年生成熟期滇重楼光合生理指标日变化和光响应参数进行了测定。结果表明：幼龄期和成熟期滇重楼叶片净光合速率（ Pn ）变化日进程在6月份出现严重午休，仅在10：00出现一个峰值；而在8、9月份上午和下午各出现一个峰值，在中午出现“午休”现象。空气温度（Ta）偏高引起气孔关闭是导致滇重楼“午休”的主要因素。成熟期滇重楼叶片在不同生长季节日均Pn和最大净光合速率（Pnmax）均高于幼龄期叶片，而幼龄期滇重楼初始量子效率较高，且光补偿点和光饱和点均低于成熟期滇重楼，对弱光的利用率更高。幼龄期和成熟期滇重楼叶片日均Pn 在8月下旬最大，其次是6月下旬，9月下旬最低，且在当年的生育后期，光饱和点有增大的趋势，由大到小的顺序为9月份、8月份、6月份。成熟期滇重楼花萼具有同叶片类似的同化功能，日均Pn 为叶片的779．％～104．0％，但其Pnmax和光饱和点均低于成熟期和幼龄期叶片的，对弱光的利用效率高于叶片。

Diurnal Changes in the Photosynthetic Characteristics of Pairs polyphylla var.yunnanensis and Its Response to Changes in Light Intensity under Different Growth Stages

We studied the diurnal changes in the photosynthetic characteristics and responses to changes in light intensity of three year-old ( juvenile stage) and eight year-old ( maturation stage) Pairs polyphylla var.yunnanensis in June ( flowering peri-od) , August ( fruit swelling period) and September ( fruit ripening period) , 2013.Both the diurnal variation of the net photosynthetic rate ( Pn ) of leaf in juvenile stage and maturation stage exhibited a single peak value at 10:00 with serious midday depression in June, and double peak values at 10:00 and 14:00 with midday depression at 12:00 both in August and September, respectively.Stomatal closure due to high air temperature was the main factor that resulted in midday de-pression of photosynthesis of P.polyphylla var.yunnanensis.During different development periods annually, both daily av-erage Pn and maximum Pn of leaf in maturation stage were higher than those in juvenile stage.The higher initial quantum yield but lower light saturation point and light compensation point of leaf in juvenile stage indicated a higher utilization effi-ciency to weak light for P.polyphylla var.yunnanensis in juvenile stage compared with that in maturation stage.Both daily average Pn of leaf in juvenile stage and maturation stage were highest in August, higher in June and lowest in September, and the light saturation point of leaf in annual later period was on an ascending trend of September>August>June.The ca-lyx of P.polyphylla var.yunnanensis in maturation stage possesses the similar assimilation function to leaf.Daily average Pn of the calyx were 77.9%-104.0%of the value of the leaf, and both the lower maximum Pn and light saturation point indi-cated high utilization efficiency to weak light for calyx.