Abstract: In usual population construction and same environmental conditions, the rates of simple leaf photosynthesis are markedly different in the same development process for the corresponding leaf order of two different genotype sorghum varieties and there is no identical trend of the rate of photosynthesis for the two varieties, if arranged in leaf order. When only one leaf remained respectively according to the leaf order, the difference of the rate of photosynthesis in the corresponding arranged leaves of two varieties still existed, but the trend showed the same if arranged in leaf order and the correlation is very marked(r=0. 862). The degree of correlation between rate of photosynthesis and yield varies with varieties, limited to the distribution direction and quantities of photosynthesis production. When photosynthesis production mainly transferred to seeds, the correlation must be striked, but if intercepted by stem and sheath or more distributed to roots, the correlation showed no striking. When the plant type of varieties changed, or the upper leaves kept erect while the lower leaves hung down loosely, the rate of photosynthesis of upper erect leaves decreased, while that of lower leaves increased compared with that of usual plant type leaves.

Key words: Sorghum, Plant type, Photosynthesis rate