2种茶树对铜胁迫的响应及其组织铜化学形态变化的比较研究

为了分析不同茶树对Cu胁迫的生理响应及其组织中不同化学形态Cu的累积特性,本研究采用水培法,探讨铁观音、肉桂2种茶树在不同浓度Cu胁迫下,茶树根系活力、叶绿素含量、茶树组织Cu含量及不同化学形态Cu含量的变化,以期为重金属对茶树毒害机理和茶树对重金属的自我防御研究提供理论依据。结果表明,随着Cu胁迫浓度的增加,茶树根系活力及叶片叶绿素含量呈现下降趋势,而与对照相比,铁观音下降的幅度远高于肉桂。不同茶树品种在相同浓度Cu胁迫下,其根、茎、叶组织的Cu含量差异不显著,而不同组织中则表现为根叶茎。不同化学形态Cu含量分析结果表明,随着Cu胁迫浓度的升高,2种茶树根部可交换态Cu、碳酸盐结合态Cu、有机结合态Cu含量百分比呈现下降趋势,而铁锰氧化态Cu和残留态Cu呈现上升趋势;茎部可交换态Cu、有机结合态Cu含量百分比呈现下降趋势,碳酸盐结合态Cu、铁锰氧化态Cu和残留态Cu呈现上升趋势;叶部可交换态Cu、碳酸盐结合态Cu、有机结合态Cu含量、铁锰氧化态Cu含量的百分比均呈现上升趋势,而残留态Cu呈现下降趋势。进一步分析发现,Cu胁迫下,铁观音茶树根、叶部主要以采取提高有机结合态Cu的形式来降低Cu离子毒害,而肉桂则以提高铁锰氧化态Cu形式降低Cu离子毒害,叶部则以提高铁锰氧化态Cu和残留态Cu的形式降低Cu离子毒害。可见,不同的茶树在Cu胁迫下所表现解毒模式存在着一定的差异。

Comparative Study on Biological Responses and Cu Speciation in Tissues of Two Different Tea Trees after Cu Exposure

In order to analyze physiological responses of different tea trees to Cu stress and accumulation characteristics of Cu with different chemical forms in different tissues of tea tree, this paper adopted water culture method, and investigated root activity, chlorophyll content, Cu content in different tissues and Cu content with different chemical forms of Tieguanyin and Rougui tea tree under Cu stress with different concentrations. It is hoping to provide theoretical foundation for studies on the mechanism of heavy metal toxicity in tea tree and self-defense of tea tree to heavy metal. Results showed that root activity and chlorophyll content of tea tree descreased with the increase of Cu concentration, but decrease of Tieguanyin was larger than Rougui as compared with the control. At the same concentration of Cu stress, Cu contents in tea tree root, shoot and leaf had no significant difference among different treatments, and followed the order as root> leaf> shoot. The content percentages of exchangeable Cu, carbonate-bound Cu, organic-bound Cu from two tea tree roots had downward trends, while Cu with Fe-Mn oxidation state and residual Cu had upward trends as stress concentration increased. Content percentages of exchangeable Cu, organic-bound Cu in the shoot decreased, and carbonate-bound Cu, Cu with Fe-Mn oxidation state, and residual Cu increased. Content percentages of exchangeable Cu, carbonate-bound Cu, organic-bound Cu and Cu with Fe-Mn oxidation state in the leaf appeared to increase, while residual Cu declined. Further analysis indicated that organic-bound Cu was mainly used to reduce Cu²⁺ toxicity under Cu stress in roots and leaves of Tieguanyin. In contrast, Rougui roots reduced Cu²⁺ toxicity by increasing Cu with Fe-Mn oxidation state and its leaves reduced Cu²⁺ toxicity by increasing Cu with Fe-Mn oxidation state and residual Cu. Thus it is indicated that detoxification patterns of different tea tree varieties are different under Cu stress.