蒙古栎叶片光合作用随叶龄的变化及其与叶片功能性状的关系

Leaf age-related changes in photosynthesis of Quercus mongolica leaves in relation to leaf functional traits

叶片光合能力直接决定着植物生产力的高低,它既受外界环境条件的影响,也受叶片内部因素的制约。本文以"日"为单位对叶龄进行度量,从爆芽日开始,对蒙古栎光合作用参数随叶龄的变化及其与叶片功能性状的关系进行了分析。结果如下:(1)蒙古栎叶片生长季初期(爆芽后3日内)其呼吸速率大于光合速率,净光合速率为负值;生长季中期,光合参数P_(max)(最大净光合速率)、J_(max)(CO2饱和时最大净光合速率)、V_(cmax)(最大Rubisco催化反应速率)的变化主要受环境因子(降雨、土壤含水率)的影响。(2)整个生长季初期,光合参数与叶绿素含量及叶面积呈极显著正相关(P<0.01);生长季初期爆芽阶段光合参数与比叶重呈负相关,生长季初期展叶阶段光合参数与比叶重呈正相关,在生长季初期叶片完全展开后,光合参数与比叶重呈负相关;生长季中期,所有的光合参数与叶片功能性状无显著相关性;生长季后期,光合参数与叶片功能性状均呈显著正相关(P<0.05)。建议今后研究中,考虑根据叶片的生长过程分阶段探讨其光合能力及其生理生化影响机制,以增加森林生态系统碳收支估算的准确性。

Photosynthetic capacity directly determines the productive capacity of plant,and it is often affected by intrinsic factors of leaves and environmental conditions.In this study,following the day scale of leaf age,the changes of photosynthetic parameters of Quercus mongolica with leaf age and their relationships with leaf functional traits from leaf budding were analyzed.We found that during the first few days after leaf budbreak,leaf respiration rate of Q.mongolica was higher than photosynthetic rate,hence the value of net photosynthetic rate was negative.The maximum net photosynthetic rate（Pmax）,the maximum net photosynthetic rate when CO2 was saturated（Jmax）,and the maximum Rubisco catalytic reaction rate（Vcmax） were influenced more greatly by environmental factors（precipitation,soil moisture） during the middle-growth period than in other periods.During the whole early growth season,the correlations among photosynthetic parameters and chlorophyll content and leaf area were extremely significantly positive（P〈0.01）,while the relationships between photosynthetic parameters and specific leaf weight were negatively correlated in leaf budding period of the early growth season,positively correlated in leaf-expansion period of the early growth season,and negatively correlated after leaf fully expanded in the early growth season.In the middle-growth season,there was no significant correlation between photosynthetic parameters and leaf functional traits.At the end of the growth season,the correlations between photosynthetic parameters and functional traits were markedly positive（P〈0.05）.Our study indicated that it was necessary to differentiate leaf photosynthetic capacities and their physiological and biochemical mechanisms following different growth stages or periods.