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

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.