棉花叶片氮含量的空间分布与光合特性

在棉花生长旺季,将冠层按高度分多层测定了田间叶片含氮量和叶片净光合速率对光合有效辐射通量密度的响应(光响应曲线,Pn-PPFD response curve)及相应的生物指标.结果表明,各层叶片氮含量与光合作用关系密切,各层平均值大小依次为上层＞中层＞下层,对应层叶片的最大净光合速率Pmax、表观暗呼吸速率Rd、光补偿点LCP及光饱和点LSP均从上到下依次递减,与氮含量分布一致,而表观光合量子效率AQY则略有不同;氮含量的指数衰减系数 kn =0.762(R2=0.593),根据观测结果,棉田叶片氮含量(N)空间分布可以用相对累积叶面积指数(Lc/Lt)为自变量的指数方程来模拟,从而为建立光合作用机理模型与进行生产力奠定基础.

The vertical distribution of cotton leaf nitrogen content and photosynthetic characteristics in the north China plain

Experimental studies on vertical distribution of cotton leaf nitrogen content per unit leaf dry mass and light response of photosynthesis (Pn-PPFD resonse curve) over canopy depth were conducted at the Yucheng Comprehensive Experimental Station of the Chinese Academy of Sciences during the period from July to August in 2007. Results show that both the mean nitrogen content and the parameters of photosynthetic characteristics including maximum net photosynthetic rate, apparent dark respiration rate, light compensation point and light saturation point decrease with canopy depth, which was divided into three layers ( top, middle and bottom ), while apparent quantum yield is a little different. Based on observations of the vertical distribution of leaf nitrogen content in the canopy on different dates, attenuation coefficient of kn 0.762 changes leaf nitrogen content with a relative cumulative leaf area index in the canopy was modeled as an exponential function.