鸢尾(Iris L．)叶片取向与其光合特性及光抑制的关系

Effects of leaf orientation on photosynthetic characteristics and photoinhibition in Iris L. seedlings

通过气体交换、叶绿素荧光、反射光谱等方法,研究了鸢尾叶片取向对植株光合特性及光抑制的影响。自然状态下,鸢尾的叶片不同取向影响植株对光能的截获;叶片净光合速率Pn与光合有效辐射PAR呈极显著相关;东西取向叶片的Pn要大于南北取向。南北取向的植株中叶片叶绿素(Chl a和Chl b),类胡萝卜素(Car)含量略高于东西取向。日进程中,各取向的叶片在一天中均没有发生明显的光抑制。相对于东西取向的植株,南北取向植株发生了明显的倾斜;在两种取向的植株中,叶片东侧和南侧的光化学反射指数(PRI)下调幅度较大;PRI的变化量(△PRI)大小依次为:东侧>南侧>西侧>北侧。鸢尾植株取向改变了叶片倾斜角度,两者共同导致光能截获减小;同时,叶片光能利用效率下调和叶黄素循环增强,这可能是不同取向植株均未发生严重光抑制的原因。

Gas exchange, chlorophyll a fluorescence kinetics and reflectance spectroscopy were investigated to explore photosynthetic characteristics and photoinhibition in Iris L. seedling leaves. Leaf orientation had a great influence on the irradiance interception of leaves under natural conditions. Net photosynthetic rate （ Pn ） in Ir/s L. seedling leaves was linearly correlated with photosynthetic active radiation （PAR）. Leaves grown with east-west orientation had a higher Pn than that in leaves grown with south-north orientation. Compared with the east-west grown leaves, the leaves grown with south-north orientation contained relatively higher chlorophyll content （Chl） and carotenoid content （Car）. During daily courses, no serious photoinhibition was induced in leaves with all orientations. Interestingly, the south-north grown leaves showed a more noticeable incline than the east-west grown leaves. In addition, photochemical reflectance index （PRI） in leaves grown with east and south orientation were significantly down regulated; changes of PRI （ΔPRI） ranked in the order of east 〉 south 〉 west 〉 north. Thus, we deduced that the co-operation of leaf orientation and the incline of leaves reduce the irradiance interception of leaves in feld ; the down-regulation of the efficiency of light energy utilization and the strengthening of xanthophyll cycle might alleviate the photoinhibion in Iris L. leaves