宝山堇菜(Viola baoshanensis)镉胁迫下的光合作用

Photosynthesis of Viola baoshanensis under Cd stress

利用荧光成像技术研究了自然生长状态下宝山堇菜、紫花地丁镉含量与光合作用间的关系。野外调查表明,宝山堇菜、紫花地丁镉含量差异显著,地上部分镉含量分别为867mg/kg和2mg/kg,相差近450倍;镉转运系数、富集系数,宝山堇菜均大于1,紫花地丁均小于1。叶绿素荧光参数,宝山堇菜Fm、Ik、Pm均显著低于紫花地丁(p=0.05);两种植物间Fo、Fv/Fm、α均无显著差异。紫花地丁地上部分镉含量与叶绿素荧光参数的相关性较低,宝山堇菜地上部分镉含量与Fm、Pm、Ik达到极显著负相关。Fv/Fm,宝山堇菜、紫花地丁均在0.8左右,与镉的相关性较低,表明其光合作用没有受到镉胁迫。但是,宝山堇菜Fm显著低于紫花地丁,而且与镉呈负相关,表明宝山堇菜叶片Fm会随镉含量的增加而降低,预示镉可能会造成宝山堇菜光系统Ⅱ叶绿素结构破坏或者抑制其电子传递。参数Ik和Pm在两种植物间差异显著及其与宝山堇菜地上部分镉含量显著负相关反映宝山堇菜光耐受能力和电子传递能力在镉胁迫下逐渐减弱。初始斜率α始终维持在较高水平,说明镉胁迫并未对宝山堇菜捕光系统造成显著伤害。结合Fm值的变化和快速光曲线中荧光参数的变化推断镉最有可能会造成宝山堇菜电子传递能力的减弱。

Although heavy metals are highly toxic accumulate heavy metals to extraordinary levels in to many plants, a number of plant species growing on metalliferous soils their tissue without showing toxic symptom. These plants are termed as hyperaccumulators, which have important value to study evolutionary, biochemistry and physiological aspects involved in the metal uptake process. Plant photosynthesis is sensitive to heavy metal stress. Nevertheless, there are only few reports of hyperaccumulators Photosynthesis under heavy metal stress. In the present study, the relationship between photosynthetic performance and Cd concentration in Viola baoshanensis and V. yedoensis was compared in the laboratory by imaging-PAM. Field survey indicated that Cd concentrations in shoots of V. baoshanensis and V. yedoensis were 867 mg/kg and 2 mg/kg, respectively. Cd accumulation factor and translocation factor in V. baoshanensis were larger than 1, while in V. yedoensis were less than 1. The results indicate the former species is a Cd hyperaccumulator, whereas the latter is not. A number of photosynthetic indexes （ Fm, Ik, Pm） of V. baoshanensis were significant lower than those of V. yedoensis, but other indexes （Fo, Fv/Fm and （ ） did not differ correlation between Cd concentrations significantly between the two species. in shoots and photosynthetic indexes. For V. baoshanensis, there was a significant significant negative correlation between Fro, Pm and Ik and Cd concentrations. The Fv/Fm of the two species was approximately 0.8, indicating there was no Cd damage on photosynthesis. However, the low Fm in V. baoshanensis indicates a negative effect of Cd on the electron transport, and/or the functioning of the chlorophyll pigments; and the low Pm and Ik in V. baoshanensis indicate Cd decreased the light tolerance and electron transport. The two species both had a high a level, indicating the normal functioning of the light absorbing system under Cd stress. Overall, the results suggest that the electron transport system of V. baoshanensis is less efficient under Cd stress.