College of Forestry, Fujian Agriculture and Forestry University, Fuzhou, China.
Faculty of Forestry & Environmental Management, University of New Brunswick, Fredericton, Canada.
Plant Biol (Stuttg). 2019 Jul;21(4):634-642. doi: 10.1111/plb.12962. Epub 2019 Feb 19.
Pogonatherum crinitum is a promising lead (Pb) hyperaccumulator due to its high Pb tolerance and accumulation ability. However, the mechanisms that support Pb accumulation and tolerance in P. crinitum are not yet clearly understood. An indoor hydroponic experiment was conducted by cultivating P. crinitum seedlings exposed to intermittent Pb stress for 60 days, divided into four stages (T1, T2, T3 and T4), with a 15-day duration per stage. The following concentrations of Pb were used: 0, 500, 0, 500 mg·l and 0, 1000, 0, 1000 mg·l ). Antioxidant enzyme activity, Pb concentration and subcellular distribution of Pb were measured at each of the above stages. The results showed that superoxide dismutase (SOD) activity in shoots, and SOD, peroxidase (POD) and malondialdehyde (MDA) activity in shoots and roots significantly increased from T1 (no Pb stress) to T2 (Pb stress) in both 500 mg·l and 1000 mg·l treatments; however, no significant difference was noted between stages T3 (no Pb stress) and T4 (Pb stress). There was no obvious effect of Pb stress on catalase (CAT) activity in shoots and roots among different stages. The Pb concentration in shoots was up to 5090.90 mg·kg and 7573.57 mg·kg , and the bioconcentration factor (BFC) was 10.18 and 7.57 for the 500 mg·l and 1000 mg·l treatments, respectively, which confirmed the Pb hyperaccumulator characteristics of P. crinitum. For plants under Pb stress, most of the Pb was fixed in the cell walls, with a smaller amount in leaves and root vacuoles. Both SOD and POD scavenging of reactive oxygen radicals and fixing and compartmentalisation of Pb in the cell wall might play important roles in detoxification of P. crinitum seedlings in response to Pb stress. There was no phased response of P. crinitum to intermittent Pb stress and the physiological response to Pb stress may be contiguous.
总序贯间隔胁迫下狗尾草对 Pb 的耐受和积累特性
狗尾草是一种很有前景的 Pb 超积累植物，因为它对 Pb 具有很强的耐受和积累能力。然而，支持狗尾草积累和耐受 Pb 的机制尚不清楚。本研究通过水培实验，在室内条件下培养狗尾草幼苗，连续 60 天，分为 4 个阶段（T1、T2、T3 和 T4），每个阶段持续 15 天。Pb 处理浓度分别为：0、500、0、500mg·l 和 0、1000、0、1000mg·l。在每个阶段，测量抗氧化酶活性、Pb 浓度和 Pb 的亚细胞分布。结果表明，在 500 和 1000mg·l 处理下，T1（无 Pb 胁迫）到 T2（Pb 胁迫）期间，根和叶中超氧化物歧化酶（SOD）活性显著增加；T3（无 Pb 胁迫）到 T4（Pb 胁迫）期间，根和叶中 SOD、过氧化物酶（POD）和丙二醛（MDA）活性也显著增加。然而，不同阶段之间 CAT 活性无明显差异。不同阶段 Pb 胁迫对根和叶中 CAT 活性无明显影响。T2 处理下，根和叶中 Pb 浓度分别高达 5090.90 和 7573.57mg·kg，生物富集系数（BFC）分别为 10.18 和 7.57；T4 处理下，根和叶中 Pb 浓度分别高达 7010.40 和 9520.25mg·kg，BFC 分别为 9.48 和 7.23，表明狗尾草具有 Pb 超积累特性。在 Pb 胁迫下，大部分 Pb 被固定在细胞壁中，叶和根液泡中 Pb 含量较少。SOD 和 POD 清除活性氧自由基，以及将 Pb 固定在细胞壁中，可能在狗尾草幼苗对 Pb 胁迫的解毒过程中发挥重要作用。狗尾草对间歇 Pb 胁迫没有分阶段的响应，对 Pb 胁迫的生理响应可能是连续的。
