不同高粱种质对污染土壤中重金属吸收的研究

Absorption of different sorghum accessions on heavy metals in polluted soil

  • 摘要: 利用重金属含量较高的污水污染土壤, 以未污染土壤作对照, 种植8个甜高粱品种、2个饲用高粱品种和1个粒用高粱品种, 检测8种重金属在高粱植物体内不同器官的含量, 以研究不同高粱种质对重金属的吸收特性。结果表明: 甜高粱对汞(Hg)、镉(Cd)、锰(Mn)和锌(Zn)的吸收在两种土壤间差异显著, 对钴(Co)、铬(Cr)、铅(Pb)和铜(Cu)的吸收差异不显著。Mn在甜高粱体内含量表现为未污染土壤高于污染土壤; 而Zn含量在不同器官之间存在差异, 未污染土壤叶中含量远高于穗, 穗中含量远高于茎和根。不同重金属在甜高粱体内的储存部位不同, 污染土壤上Hg、Cd、Co、Cr和Zn在根中积累量较高, Cu、Mn和Pb在穗中的积累量较高。甜高粱、饲用高粱和粒用高粱对重金属的吸收、运输及储存在品种之间差异较大, 同一品种对不同重金属的吸收也存在差异。饲用高粱表现为叶部对Cr和Zn的储存量较高, 而粒用高粱'晋中0823'则显示了茎对多种重金属的储存能力。高粱根对土壤中重金属的富集系数较高, 为0.02(Pb)~0.23(Cd), 转移系数变幅为0.21(Co)~3.42(Pb)。对同一种重金属的吸收量品种间差异较大, 甜高粱'西蒙'根对Co、Cr、Cu、Mn、Pb和Zn具有高富集系数, 粒用高粱'晋中0823'茎对Hg、Cd、Mn、Pb和Zn富集系数较高。高粱对重金属的吸收能力与转移能力不同步, 甜高粱'绿能1号'具有对多种重金属的高转移能力, 粒用高粱'晋中0823'只对Zn有较高的转移能力。因此本文认为甜高粱对不同重金属的吸收和转移有选择性。对Zn吸收并转移到地上部后, 首先储存在叶和穗中, 当吸收量足够大时, 茎和根也成为储存器官; 对Mn的吸收与其他重金属的吸收存在竞争作用, Hg吸收后很少向地上部转移; 而对Cu、Mn和Pb吸收后在穗部的储存量较大。饲用高粱与甜高粱相比对重金属的吸收未显示明显的不同, 甜高粱'西蒙'根对多种重金属具有强储存能力, 而粒用高粱'晋中0823'的茎秆显示了比甜高粱更强的储存能力, 甜高粱'绿能1号'对多种重金属的转移能力较强。所以, 选择富集和转移能力均强的高粱品种能更有效地吸收土壤中的重金属, 达到修复污染土壤的目的。

     

    Abstract: Sweet sorghum, which is used to produce alcohol and energy, hardly enters human food chain. This purpose combined with powerful root uptake ability makes sweet sorghum a low-cost, safe and effective plant in removing heavy metals (HMs) from polluted soils. In this study, eight sweet, two forage and one grain sorghum accessions planted in polluted soil were evaluated and compared with those planted in unpolluted soil. Eight HMs were evaluated in different plant organs to characterize HMs uptake ability of different sorghum accessions. The results showed that contents of Hg, Cd, Mn and Zn in sweet sorghum accessions were significantly different in polluted and unpolluted soil. However, the contents of Co, Cr, Pb and Cu were not significantly different. Mn content in sweet sorghum accessions in unpolluted soil was higher than that in polluted soil. Zn content was much higher in leaves and spikes than in stems and roots of plants from unpolluted soil, much different from that of plants from polluted soil. HMs contents varied in different sweet sorghum organs. For instance, there were high contents of Hg, Cd, Co, Cr and Zn in plant root while high contents of Cu, Mn and Pb were in plant spike in polluted soil. Significant differences existed in uptake, transfer and accumulation of HMs both among different accessions and HMs. Forage sorghum 'Wancao 2' had more Cr and Zn in leaves while 'Jinzhong 0823' grain sorghum accession had more heavy metals in stems than other accessions. High HMs enrichment coefficients were existed in the root of sorghum, which ranged from 0.02 (for Pb) to 0.23 (for Cd), and transfer coefficients were 0.21 (for Co) to 3.42 (for Pb). Significant differences existed among accessions in terms of certain HM uptake. Enrichment coefficients of Co, Cr, Cu, Mn, Pb and Zn in root of 'Ximeng' sweet sorghum were high. Also enrichment coefficients of Hg, Cd, Mn, Pb and Zn in stem of 'Jinzhong 0823' grain sorghum were high. The ability of HMs enrichment and transfer was not consistent in sorghum accessions, such as 'Lüneng No.1' sweet sorghum had a high transfer coefficient for several HMs, only Zn had high transfer coefficient in 'Jinzhong 0823' grain sorghum. Thus the result above suggested that the enrichment and transfer of HMs varied with HM types in sweet sorghum. Sweet sorghum first absorbed Zn and then accumulated it in leaves and spikes, and then in stems and roots as Zn content of the plant was high enough. Mn uptake of sweet sorghum competed with other HMs. Hg was seldom transferred to above-ground parts after its uptake by sweet sorghum, while Cu, Mn and Pb mainly accumulated in sweet sorghum spikes. 'Ximeng' sweet sorghum had a rich accumulation of several HMs in roots, while large amounts of various HMs accumulated in stems of 'Jinzhong 0823' grain sorghum accession. There was no specific pattern of HMs uptake in forage and sweet sorghum accessions. Therefore, sorghum plant could be used to remove HMs from polluted soils. This could be more efficiently done by employing accessions with high HM enrichment and transfer ability.

     

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