淮北棉区花铃期冠层不同高度叶片光合特性的差异

基于多层二叶模型,在自然群体条件下,将棉花冠层分为上、中、下三层,研究淮北棉花花铃期冠层上、中、下层,阴叶（无直射光照射）与阳叶（有直射光照射）的光合特性的差异。结果表明,同一高度阳叶的光量子通量密度与光合速率显著大于阴叶;不同高度叶片光量子通量密度与光合速率均表现为上层阳叶〉中层阳叶〉下层阳叶,上层阴叶〉中层阴叶〉下层阴叶;上层阳叶气孔导度大于阴叶,中、下层阴、阳叶的气孔导度无显著差异;上部叶片气孔导度〉中部叶片〉下部叶片;同一高度阳叶胞间二氧化碳浓度显著小于阴叶,随着冠层深度（形态学自上而下）的增加,两者差异增大;不同高度叶片胞间二氧化碳浓度随着冠层深度的增加,呈增加趋势,阳叶差异不显著,阴叶差异显著。

Difference of Photosynthetic Characteristics of Different Height Leaves in the Cotton Flower-boll Development Phase in Huaibei Area

Under natural population condition, photosynthesis of sunlit and shaded leaves at different heights of cotton canopy was measured by a portable photosynthetic gas analysis system LI-6400 in Huaibei cotton area. The results show that a sunlit leaf had a significantly higher photons flux density (PFD),net photosynthetic rate(Pn)than a shaded leaf at the same height.PFD and Pn of a sunlit(sha-ded)leaf were the highest in upper canopy the next in middle canopy,and the lowest in basal canopy. A sunlit leaf in upper canopy had a larger stomatal conductance(Gs)than a shaded leaf, but leaf in middle or basal canopy had a similar Gs no matter what it was a sunlit or shaded leaf.The Gs of leaf was the largest in upper canopy,the next in middle canopy,and the least in basal canopy.A sunlit leaf had a significantly lower intercellular CO_2 concentration(Ci)than a shaded leaf at the same height;the difference between the both became larger and larger as the depth of the canopy increased.Difference in Ci between sunlit leaves was not significant,but significant between shaded leaves as the depth of the canopy increased