多年生黑麦草抗氧化酶和植物络合素对Cd^(2+)胁迫的应答

Responses of antioxidative enzymes and phytochelatins in Lolium perenne to Cd^(2+) stress

采用水培方法研究了5 mg·L-1Cd2+胁迫下,Cd在多年生黑麦草中的积累和Cd2+对多年生黑麦草抗氧化酶活性和植物络合素等巯基化合物浓度的影响。将具有3片展开叶的多年生黑麦草实生苗转至1/2霍格兰营养液中培养2周后,对其进行5 mg·L-1Cd2+处理,分别在处理后的0、0.25、1、3、6 d取样测定根系和叶片的Cd浓度、抗氧化酶活性和植物络合素等巯基化合物的浓度。结果表明,Cd2+处理多年生黑麦草6 d后,根系中Cd浓度达到2.59 mg.g-1,叶片中Cd浓度达到0.24 mg.g-1,根中Cd向叶片的转运系数为0.093,叶中Cd的富集系数为48,多年生黑麦草属Cd高积累植物,具备在植物修复上应用的前景。Cd2+胁迫下,多年生黑麦草根叶中丙二醛(MDA)含量无显著变化,根中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性无显著变化,抗坏血酸过氧化物酶(APX)对Cd2+敏感,处理后6 d活性较0 d显著下降67.19%。Cd2+处理1 d内,叶中SOD、APX、CAT活性显著降低。Cd2+处理后3 d,叶中的抗氧化酶系统对叶中Cd浓度的升高做出了正反馈,SOD、APX、CAT的活性分别较处理后1 d显著上升了14.19%、76.82%、99.26%,Cd2+处理时间延长至6 d,SOD活性较处理后3 d显著下降了18.58%,APX、CAT活性无显著变化。Cd2+处理后6 d,多年生黑麦草根中半胱氨酸(Cys)、谷胱甘肽(GSH)、植物络合素2(PC2)、植物络合素3(PC3)、植物络合素4(PC4)、植物络合素5(PC5)和植物络合素6(PC6)浓度分别较处理0 d提高了2.19、1.57、2.06、16.08、5.73、6.03和4.31倍,叶中Cys、GSH、PC2、PC3和PC4浓度分别较处理0 d提高了0.69、3.21、1.64、5.73和0.27倍。根中PC3巯基比例最大,叶中GSH的巯基比例最大,二者是根、叶中巯基存在的主要形式。随着Cd2+处理时间的延长,根系和叶片中各巯基化合物的总巯基浓度显著升高,根系和叶片中植物络合素总巯基浓度与Cd浓度显著正相关。多年生黑麦草通过植物络合素等巯基化合物的快速合成降低了根叶中自由Cd2+的比例,保护了根叶中抗氧化酶的活性,间接维持了活性氧代谢的平衡。

服务 把本文推荐给朋友 加入我的书架 加入引用管理器 E-mail Alert RSS A hydroponics experiment was conducted to study the Cd accumulation in Lolium perenne and the effects of the accumulated Cd on the activities of antioxidative enzymes and the concentrations of phytochelatins under Cd^2＋ stress. The L. perenne plants with three fully expanded leaves were cultured in 1/2 Hoagland＇s nutrient solution for 2 weeks, and then treated with 5 mg·L^-1 of Cd^2＋. The Cd concentration, antioxidative enzymes activities, and thiol compounds concentrations in both roots and leaves were measured on the day 0, 0.25, 1, 3, and 6 after treatment. After 6 days, the Cd concentration was 2588 mg·kg^-1 in roots and 240 mg·kg^-1 in leaves. The Cd transport index from root to leaf was 0.093, and the Cd bioconcentration index of leaf was 48, indicating that L. perenne had a high Cd accumulation capacity, and could be applied in phytoremediation. After exposed to Cd^2＋ stress, the MDA content in L. perenne leaves and roots and the SOD and CAT activities in L. perenne roots had less change, but the root APX was highly sensitive to Cd^2＋, with the activity on day 6 decreased significantly by 67%, as compared with that on 0 day. Within 1 day Cd^2＋ exposure, the SOD, APX and CAT activities in leaves decreased significantly. On day 3, the antioxidative enzyme system in leaves had a positive feedback to the increase of leaf Cd content, and the SOD, APX, and CAT activities increased significantly by 14%, 77%, and 99%, respectively, as compared with day 1. On day 6, the SOD activity decreased significantly by 19%, as compared with day 3, but the APX and CAT activities had no significant change. On day 6, the concentrations of Cys, GSH, PC2, PC3, PC4, PC5, and PC6 in roots were 2.19, 1.57, 2.06, 16.08, 5.73, 6.03, and 4.31 times higher, and the concentrations of Cys, GSH, PC2, PC3, and PC4 in leaves were 0.69, 3.21, 1.64, 5.73, and 0.27 times higher than those on day 0, respectively. PC3 thiol had the greatest proportion to total thiol in roots, whereas GSH thiol had the greatest proportion to total thiol in leaves, suggesting that PC3 thiol and GSH thiol were the main existence forms of thiol in roots and leaves, respectively. With the increasing time of Cd^2＋ treatment, the total thiol concentration both in roots and in leaves increased significantly, and the total PCs-SH concentration in roots and leaves was significantly positively correlated with the Cd concentration in roots and leaves. It was suggested that L. perenne could rapidly synthesize thiol compounds to decrease the proportion of Cd^2＋ to total Cd in leaves and roots, which played a key role in protecting the antioxidative enzymes in roots and leaves, and indirectly maintained the balance of reactive oxygen metabolism.