白榆-刺槐互作条件下叶片养分与光合生理特性

以一年生实生苗白榆(Ulmus pumila.)和刺槐(Robinia pseudocacia.)为供试材料,采用盆栽法,研究了白榆-刺槐在互作条件下其叶片的养分特性与光合生理特性。分别测定在单作及互作条件下,白榆和刺槐植物叶片的氮、磷含量、氮磷比值及叶绿素相对含量(Chl)、光合气体交换参数和叶绿素荧光参数。结果表明,白榆-刺槐互作较单作提高了叶片的N含量,而两种不同栽植方式对白榆或刺槐的叶P含量影响较小;互作处理中,白榆叶片的Chl和净光合速率(Pn)大于刺槐且均高于其相应的单作;白榆的PSⅡ最大光能转换效率(Fv/Fm)和可变荧光与初始荧光之比(Fv/Fo)均高于刺槐,且互作高于其单作处理,说明互作较单作提高了叶片PSⅡ的潜在活性,增加了PSⅡ的光能转化效率;两种植物不同的栽植方式对光化学猝灭系数(qp)的变化影响较小,而互作刺槐非光化学猝灭系数(NPQ)显著高于其单作,这表明互作刺槐叶片PSⅡ的潜在热耗散能力较强,这是一种叶片为免受光破坏的保护机制,它可有效地避免过剩光能对光合机构的损伤。

Leaf nutrient contents and photosynthetic physiological characteristics under Ulmus pumila and Robinia pseudocacia mixed plantation

Pot experiments were used to study the leaf nutrient status and photosynthetic physiological characteristics under Ulmus pumila and Robinia pseudocacia mixed plantation.The leaf nitrogen(N),leaf phosphorus(P),ratio of N/P and chlorophyll contents(Chl),photosynthetic gas exchange parameters and chlorophyll fluorescence parameters were measured under U.pumila monoculture,R.pseudocacia monoculture and U.pumila-R.pseudocacia mixed plantation conditions.The results showed that the leaf N contents under the mixed plantation were higher than those in monocultures,but the changes of leaf P contents of U.pumila or R.pseudocacia were smaller under the two different planting ways.Chl and photosynthetic rates(Pn) of U.pumila were higher than R.pseudocacia under the mixed plantation and they were also higher than in monocultures.The Fv/Fm and Fv/Fo of U.pumila were higher than R.pseudocacia and they were also higher than in monocultures.It showed that the leaf PSⅡ potential activity was improved and light energy conversion efficiency of PSⅡ was increased under the mixed plantation than in monocultures.Two different planting methods had little effect on qp,and the NPQ of R.pseudocacia under the mixed plantation was significantly higher than in monocultures.It indicated that the PSII potential heat dissipation capacity of R.pseudocaciaa was much higher,which might be a kind of protection mechanism protecting the leaf away from light damage.This can effectively avoid the damage of excess light energy to photosynthetic apparatus.