铺地黍Zn的累积特性及其亚细胞分布和化学形态特征

Accumulative Characteristics, Subcellular Distribution, and Chemical Forms of Zn in Panicum repens

摘要:

为探明铺地黍(Panicum repens)对Zn的耐受机制和动态迁移规律，通过水培盆栽试验研究其根、茎、叶的Zn累积、转运能力及Zn亚细胞和化学态分布特征。结果表明，铺地黍的根、茎、叶的最高Zn含量分别为2 728.38、388.63和1 199.07 mg/kg, 其富集系数(最高为3.11)均超过国际超富集植物指标限值。茎→叶的平均迁移率(264.99%)远大于根→茎的(14.16%)。随胁迫时间延长和Zn处理浓度的增大，茎叶的Zn含量均显著增加(P<0.05)。根的Zn含量变化呈“Λ”型，在21 d达到最高值。根和叶主要通过细胞壁固定(占比超过58%)解毒Zn伤害，茎主要通过液泡区室化解毒。根和叶中的Zn主要以NaCl提取态存在，其最高占比分别达到75.40%和61.05%，其次是有机态(HAc和HCl)，其主要通过分配更多的Zn到活性较低的化学态存储来减少伤害。而茎的Zn主要以活性较高的ethanol和d-H₂O态存在，其较高的Zn离子流动性增强了茎→叶运输作用，因此导致叶部Zn含量较高。铺地黍呈现出很强的Zn耐受和累积能力，具备生态修复热带亚热带地区重度Zn污染河岸消涨带的潜力与优势。

Abstract:

In order to explore the tolerance mechanism and dynamic migration of Zn in torpedograss (Panicum repens), the accumulation and transport capacity of Zn in roots, stems and leaves, as well as the distribution characteristics of Zn subcellular and chemical states were studied by hydroponic pot experiment. The results showed that the maximum Zn contents in roots, stems, and leaves were 2 728.38, 388.63 and 1 199.07 mg/kg, respectively, and their enrichment factors (with a maximum of 3.11) all exceeded the international limit for super-accumulating plants. The average migration rate from root to leaf (264.99%) was much higher than that from stem to leaf (14.16%). With the extension of stress time and the increase of Zn concentration, the Zn contents in stems and leaves significantly increased (P<0.05). However, the change in Zn content of root showed a “Λ” type, reaching the highest value at 21 days. The roots and leaves were detoxicated mainly by cell wall fixation (more than 58%), while the stems were detoxicated mainly by vacuole compartments. The Zn in the roots and leaves mainly exists in the NaCl extraction state, with the highest proportions of 75.40% and 61.05%, respectively, followed by organic state (HAc and HCl), which mainly reduces the damage by allocating more Zn to the less active chemical state storage. The Zn in stems is mainly in the form of ethanol and d-H₂O with high activity, and the higher fluidity of Zn ions enhances the transport from stem to leaf, resulting in higher Zn content in leaves. Therefore, Panicum repens exhibits strong Zn tolerance and accumulation capacity, and has the potential and advantage of ecological remediation of heaviy Zn-contaminated water-level-fluctuation zones in tropical and subtropical regions.