绿化树种白玉兰的光合特性

测定了白玉兰树冠不同生长时期、不同部位净光合速率的日变化和季节变化及叶绿素含量。结果表明，生长初期净光合速率除阳面上冠层为双峰曲线外，其他冠层呈单峰曲线；盛期呈多峰曲线；末期阳面冠层呈多峰曲线，阴面冠层呈双峰曲线。净光合速率的季节变化表现为：盛期＞末期＞初期。初期方位和冠层对净光合速率的影响均不显，盛期均极显，末期冠层影响显。另外，还对影响净光合速率的因子以及叶绿素含量作了分析。

A Study on the Photosynthetic Characteristics of Magnolia Denudata

Diurnal changes and seasonal changes of net photosynthetic rate( Pn )and chlorophyll concentration of Magnolia denudata leaf in different growing stages and different positions of crown were studied.The results revealed that there is a single apex for Pn at initial growing stage,except upper part of crown in sunshine side is double apex.many apex at fast growing stage,crown in sunshine side is many apex and crown in shade side is double apex at last growing stage.The Pn at fast growing stage at greater than that at last growing stage,and that at last growing stage was greater than that was initial growing stage.The effects of direction and position of crown on Pn at initial growing stage was not notable,the effects of which at fast growing stage were very notable,the effects of position at last growing stage was notable.The factors effecting net photosynthesis rate and the content of chlorophyll also were analysed.