夏玉米群体光合速率特性及其与冠层结构、生态条件的关系

研究结果表明：高产夏玉米群体光合速率日变化呈单峰曲线。在水肥充足栽培条件下，光照强度是影响玉米群体光合速率的主导因素，最大自然光强下群体光合未测到光饱和点。群体光合速率随CO2浓度(50—900ppm范围)的增加而提高。土壤呼吸释放的CO2量占群体光合速率的11.68%。高产群体所形成的独特环境对单叶光合速率影响很大，群体生长下的单株，在8×104一9×104Lx光下的单叶光合速率为果穗叶高于下部和上部叶，品种、密度间差异不大；冠层自然状态下的单位叶面积光合速率上部叶却高于中、下部叶，高密度下，紧凑型品种高于平展型品种，低密度下则相反。

THE CHARACTERISTICS OF CANOPY PHOTOSYNTHESIS OF SUMMER CORN(ZEA MAYS)AND ITS RELATION WITH CANOPY STRUCTURE AND ECOLOGICAL CONDITIONS

The present study was carried out during 1989-1990 in high yield summer corn field. The results were as follows:Diural course of canopy apparent photosynthesis (CAP) rate was a unimedal curve(11:00-12:00). The relationship between light intensity and CAPrate showed rectangular hyperbola. The light compensition point of CAP was about 4000 Lx. No light saturation point observed under field condition. CAP increased with CO_2 concentration from 50 to 900ppm. The ratio of CO_2 assimilated to that released from the soil was 11.68% througout growth period. Photosynthetic rate of ear leaf was higher than the sixth leaf and the leaf next to the top leaf when leaf was expose fully to light, but there was no di- fference among cultivares and plant densities, Leaf photosynthetic rate was in the order of top leaves>middle leaves>base leaves under natural state and vertical leaf type cultivar>horizonal under high density condition.