Cu胁迫下基质中凹凸棒石粘土对当归幼苗的保护作用

Protective effects of attapulgite clay on Angelica sinensis seedlings under Cu stress

在含有不同比例凹凸棒石粘土的混合基质中(凹凸棒石粘土∶基质的体积比分别为0∶1、1∶100、1∶70、1∶50、1∶20)培育当归幼苗,以研究Cu胁迫对当归幼苗的生理学影响及凹凸棒石粘土对Cu胁迫下当归幼苗的保护作用。结果表明:(1)基质中不存在凹凸棒石粘土时,随着CuCl2处理浓度的上升,当归幼苗叶片的实际光化学效率[Y(Ⅱ)]、PSⅡ电子传递速率(ETR)、光化学淬灭(qP)和叶绿素含量都逐渐降低;而叶片的非光化学猝灭(qN)、可溶性蛋白含量、抗氧化酶活性(SOD、POD、CAT、APX)、过氧化氢含量以及根和叶片中的Cu含量均显著性增加,表明Cu胁迫降低了当归幼苗的光化学效率、叶绿素的合成、增加了组织中Cu含量和氧化压力。(2) CuCl2胁迫下,当基质中存在不同比例的凹凸棒石粘土时,Cu胁迫所导致的叶片Y(Ⅱ)、ETR、qP及叶绿素含量的降低以及叶片qN、可溶性蛋白含量、抗氧化酶活性、过氧化氢含量、根和叶片的Cu含量的升高均有所缓解,说明凹凸棒石粘土通过吸附或固定基质中游离的以及可交换的Cu离子,减少了当归幼苗对有效Cu离子的吸收,从而缓解了Cu离子对植物造成的生理学压力,且这种缓解作用依次为1∶70> 1∶50> 1∶20≥1∶100> 0∶1,这是基质中存在过多的凹凸棒石粘土时,其在吸收基质中Cu离子的同时也会影响基质的通气性、透水性和酸碱度等。这表明凹凸棒石粘土在基质中的适当加入能缓解Cu胁迫对当归幼苗造成的的生理学压力。

Seeds of Angelica sinensis were planted in a matrix containing different proportions of attapulgite clay (the volume ratio of attapulgite clay and matrix was 0∶1, 1∶100, 1∶70, 1∶50, 1∶20) to study the physiological effects of Cu stress on A. sinensis seedlings and the protective effect of attapulgite clay on A. sinensis seedlings under CuCl 2 stress. The results were as follows:(1) With the increase of exogenous CuCl 2 concentration, Y(Ⅱ)(PS Ⅱ operation efficiency), ETR (rate non-cyclic electron transport through PS Ⅱ), qP (photochemical quenching), and chlorophyll content of leaves of A. sinensis seedlings decreased, while the qN (non-photochemical quenching), soluble protein content, activities of antioxidant enzymes (SOD, POD, CAT, and APX), the content of H 2 O 2 and the CuCl 2 content in the leaves and roots increased significantly. The results showed that the Cu stress decreased in both photochemical efficiency and chlorophyll synthesis of A. sinensis seedlings, and increased the content of Cu and oxidation pressure in tissues.(2) Under Cu stress, the presence of attapulgite clay in the growth matrix could alleviate the copper-stress-induced decreases in the Y(Ⅱ), qP, ETR , and chlorophyll content of the leaves, and could alleviate the copper-stress-induced increases of the qN , soluble protein content, activities of antioxidant enzymes, content of H 2 O 2 as well as copper contents in the leaves and roots. Our results indicate that the attapulgite clay can reduce the absorption of available Cu 2+ by adsorbing or immobilizing free and exchangeable Cu 2+ in the matrix, thus relieving the physiological pressure caused by Cu 2+ on plants, which is propitious to its growth. And in the order of the mitigation is 1∶70 > 1∶50 > 1∶20 ≥ 1∶100 > 0∶1, this is due to the fact that when there is too much attapulgite clay in the matrix, the absorption of Cu 2+ in the matrix will also affect the original physical properties of the matrix such as aeration, permeability and pH and so on. These results together manifest that the attapulgite clay in the matrix can alleviate the copper-induced physiological stress on A. sinensis seedlings.