重金属铅胁迫对人参光合特征与皂苷含量的影响

Effects of lead stress on net photosynthetic rate,SPAD value and ginsenoside production in Ginseng( Panax ginseng)

为阐明Pb胁迫对人参光合作用与次生代谢产物的影响,探讨药用植物对重金属胁迫的响应机制,采用筒栽试验方法,对不同浓度铅（Pb）处理（0,100,250,500,1 000 mg·kg-1）下人参的光合特征参数与皂苷含量进行了测定与分析。结果表明,低浓度Pb处理（≤250 mg·kg-1）时,人参叶片净光合速率和SPAD的变化并不显著,当Pb质量分数达到500 mg·kg-1时,叶片净光合速率和SPAD均显著下降（P〈0.05）,当Pb质量分数为1 000 mg·kg-1时,二者达到最低,降低幅度分别为57.8%,11.0%。从人参根部总皂苷含量来看,Pb胁迫浓度为100 mg·kg-1时,总皂苷含量的变化并不显著,而当Pb质量分数达到250 mg·kg-1时,总皂苷含量显著增加（P〈0.05）,并在Pb质量分数为1 000 mg·kg-1时,达到最高。在Pb质量分数为0~1 000 mg·kg-1时,Pb浓度与叶片净光合速率和SPAD均呈现极显著的负线性相关（P〈0.01）,而与人参总皂苷含量呈现出显著的正线性相关关系（P〈0.05）。由此说明,人参叶片光合作用与根部次生代谢对Pb胁迫的响应规律是反向的,高浓度Pb胁迫将抑制人参叶片的光合能力,但能够促进人参根部的次生代谢过程。

The paper aimed to evaluate the effects of lead stress on photosynthetic performance and ginsenoside content in ginseng（ Panax ginseng）. To accomplish this,three years old ginseng were cultivated in pot and in phytotron with different concentrations of lead,ranging from 0 to 1000 mg·kg- 1soil for a whole growth period（ about 150 days）. The photosynthetic parameters in leaves and ginsenoside content in roots of ginseng were determined in green fruit stage and before withering stage,respectively. In comparison with the control,net photosynthetic rate and SPAD value in ginseng leaves cultivated with 100 and 250 mg·kg- 1of lead changed insignificantly,however,ginseng supplied with 500 and 1 000 mg·kg- 1of lead showed a noticeably decline in the net rate of photosynthesis and SPAD value（ P 〈 0. 05）,the lowest net photosynthetic rate and SPAD value showed in the treatment supplied with 1 000 mg·kg- 1of lead,with decline of 57. 8%,11. 0%,respectively. Total content of ginsenoside in ginseng roots cultivated with 100 mg·kg- 1of lead showed insignificantly change compared to the control,but the content increased remarkably in treatments supplied with 250,500,1 000 mg·kg- 1of lead（ P 〈 0. 05）,and highest content appeared in these ginsengs exposed to 1000 mg·kg- 1of lead. The net photosynthetic rate and SPAD value in leaves of ginseng both showed significantly negative linear correlations with lead stress level（ P〈 0. 01）,and significant positive linear correlations between total content of ginsenoside and lead concentration was also observed（ P〈 0. 05）. These results strongly indicate that exposing to high level of lead negatively affects photosynthetic performance in ginseng leaves,but benefits for accumulation of secondary metabolism（ total content of ginsenoside） in ginseng root.