外源植物激素喷施对三叶鬼针草修复镉污染土壤的影响

Effects of Exogenous Plant Hormone Spraying on the Phytoremediation by Bidens pilosa L.in Cadmium-contaminated Soil

为了探究外源植物激素喷施对超积累植物吸收重金属的影响,以三叶鬼针草(Bidens pilosa L.)为供试植物,通过叶面喷施3种不同浓度的6-苄基腺嘌呤(6-BA)、水杨酸(SA)和24-表油菜素甾醇(24-EBR),研究外源植物激素喷施对三叶鬼针草修复镉(Cd)污染的影响.结果表明,分别喷施适宜浓度的3种外源植物激素:①高效强化三叶鬼针草修复Cd污染土壤效果,使植株叶部Cd含量分别增加4.21%、31.79%和14.89%,使转运系数(TF)分别提高9.67%、18.83%和17.85%,使植株提取效率(PR)分别提高15.36%、32.33%和64.38%;②显著促进三叶鬼针草的生长,使植株地上部干重分别增加了37.53%、74.50%和104.02%;③显著增强三叶鬼针草的光合作用,使植株叶绿素a含量分别提高了79.31%、92.27%和51.12%,此时光化学猝灭系数(qP)分别提高11.32%、89.16%和78.43%,非光化学猝灭系数(NPQ)分别提高51.71%、241.12%和27.85%;④显著强化三叶鬼针草抗氧化能力,使得植株丙二醛(MDA)浓度分别降低了62.41%、68.67%和46.76%,使超氧化物歧化酶(SOD)活性分别提高了68.33%、10.28%和6.17%,过氧化氢酶(CAT)活性分别提高了31.43%、37.87%和37.31%.综上所述,Cd胁迫下喷施适宜浓度的外源6-BA、SA和24-EBR可显著提高三叶鬼针草生物量,促进重金属在植株体内富集;提升植株光合作用能力,降低重金属胁迫对植株的氧化损伤,增强抗氧化能力,提高植株对于Cd的吸收和耐受性;促进植株根部Cd向地上部转移,提高植株对重金属Cd的提取效率,高效强化植株修复效果,其中以30 mg·L^(-1)SA叶面喷施效果最佳.

To explore the effect of exogenous plant hormone spraying on the absorption of heavy metals by hyperaccumulated plants,Bidens pilosa L.was selected as the tested plant owing to the large biomass,short growth cycle,and high accumulation efficiency.Here,the effect of foliar spraying 6-benzylaminopurine(6-BA),salicylic acid(SA),and 24-epi-brassinosteroid(24-EBR)on the remediation of cadmium(Cd)-contaminated soil by B.pilosa L.was examined.The results showed:①the efficiency of the remediation in Cd-contaminated soil by B.pilosa L.was effectively enhanced after the spraying of all three kinds of exogenous plant hormones with appropriate concentrations.The spraying of the three exogenous plant hormones could promote the cadmium concentration in the leaves of B.pilosa L.to increase by 4.21%,31.79%,and 14.89%;promote the translocation factor(TF)to increase by 9.67%,18.83%,and 17.85%;promote the phytoextraction rates(PR)to increase by 15.36%,32.33%,and 64.38%,respectively.②The growth of B.pilosa L.was significantly promoted after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations.The spraying of the three exogenous plant hormones could promote plant growth under cadmium stress,and the dry weight of the plant root,stem,and leaf was increased by 37.53%,74.50%,and 104.02%,respectively.③The photosynthesis of B.pilosa L.was significantly enhanced after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations.The chlorophyll concentration of the plant was significantly increased after foliar spraying with plant hormones,and the concentration of chlorophyll a was increased by 79.31%,92.27%,and 51.12%;the photochemical quenching coefficient(qP)was increased by 11.32%,89.16%,and 78.43%;and the non-photochemical quenching coefficient(NPQ)was increased by 51.71%,241.12%,and 27.85%,respectively,after foliar spraying with appropriate concentrations of 6-BA,SA,and 24-EBR.④The antioxidant capacity of B.pilosa L.was significantly strengthened after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations.The malondialdehyde(MDA)concentration of the plant was reduced by 62.41%,68.67%,and 46.76%after the application of 6-BA,SA,and 24-EBR,respectively.Meanwhile,superoxide dismutase(SOD)was increased by 68.33%,10.28%,and 6.17%,and catalase(CAT)was increased by 31.43%,37.87%,and 37.31%,respectively.Generally,the spraying of exogenous 6-BA,SA,and 24-EBR with the appropriate concentration under Cd stress could significantly increase the biomass of B.pilosa L.and promote the accumulation of heavy metals in the plant,improve the photosynthetic ability of the plant,reduce the oxidative damage of the plant under heavy metal stress,enhance the antioxidant capacity,and improve the absorption and tolerance of plants to Cd.It also could promote the transfer of Cd from roots to shoots,improve the phytoextraction rates of Cd from the plant,and effectively strengthen the phytoremediation efficiency.Among them,30 mg·L^(-1)SA foliar spraying had the best effect.