不同铅吸收特性小麦Pb的亚细胞分布和化学提取态

【目的】研究铅(Pb)胁迫下小麦百农160和偃展4110体内Pb亚细胞分布和化学提取态变化,为Pb低积累品种筛选提供理论依据。【方法】以前期筛选的对Pb吸收有明显差异的2个小麦品种(百农160和偃展4110)为试验材料,采用砂培试验,以Pb(NO3)2作为铅源,分别设置0(对照)、100和800 mg?L-1共3个处理水平,胁迫4周后,收获并测定小麦生物量、Pb亚细胞分布及化学提取态含量,分析比较2种铅吸收特性小麦Pb的亚细胞分布和化学提取态特征。【结果】100 mg?L-1Pb胁迫对小麦生长有促进作用,百农160和偃展4110生物量均有所增加,增幅分别为4.78%和2.66%。800 mg?L-1Pb胁迫下,小麦生长受到抑制,百农160和偃展4110生物量均显著降低,分别降低了25.66%和38.60%。此外,2种小麦根冠比的变化也存在一定差异,当介质中Pb的浓度从100增至800 mg?L-1后,百农160根冠比无明显变化,而偃展4110则表现出一定程度的增加,由0.71增至0.81。Pb胁迫4周后,百农160茎叶和根系中的Pb含量均低于偃展4110。就亚细胞分布而言,2种小麦体内Pb主要存在于细胞壁和细胞液中,其合量占小麦体内Pb总量的72%—86%。当介质中Pb浓度从100 mg?L-1增至800 mg·L-1后,偃展4110根细胞壁和细胞液中Pb所占比例降低8%,茎叶这一比例降低4%,而百农160根中这一比例增加了9%,茎叶则增加了1%。就Pb的化学提取态而言,小麦体内(茎叶和根系)Pb以难溶性的醋酸提取态和盐酸提取态为主,两者占总和的67%—85%,氯化钠提取态含量次之,占总和的6%—18%,乙醇提取态、去离子提取态和残渣态含量较低,3种形态占总和的8%—16%。此外,100和800 mg?L-1Pb胁迫下,百农160根中活性较强的乙醇提取态和去离子水提取态Pb含量均低于偃展4110。然而,2种小麦茎叶中活性态合量特征与根中有所不同,100 mg?L-1 Pb处理下,百农160茎叶活性态合量低于偃展4110,当胁迫增至800 mg?L-1Pb时,2种小麦茎叶中活性态合量无明显差异。【结论】铅胁迫下,百农160的根表对Pb的阻碍能力强于偃展4110,同时将进入体内的Pb更大比例固定在细胞壁上,以减少Pb向地上部的运移,从而减轻Pb对地上部的毒害作用。就化学提取态而言,各形态的分配比例与Pb的解毒机理关系密切,但不同器官表现有所差异。

Subcellular Distribution and Chemical-Extraction of Lead in Wheat with Different Characteristics of Lead Absorption

【Objective】The objectives of this study were to examine the subcellular distribution of lead (Pb) and various chemical extraction in wheat cultivars Bainong160 and Yanzhan4110, to provide theoretical support for screening for cultivars of wheat with low Pb accumulation. 【Method】Based on a preliminary investigation, two wheat cultivars with different characteristics of Pb absorption were selected as study materials. A sand-culture experiment was carried out at three levels of Pb stress: 0 (control), 100 and 800 mg·L^-1 Pb as Pb (NO₃)₂. After 4-week Pb stress, the plant was harvested. Biomass, subcellular distribution and chemical extraction of Pb were determined, and the differences in biomass, subcellular distribution and chemical extraction of Pb between two wheat cultivars under Pb stress were analyzed. 【Result】 Pb at 100 mg·L^-1 could improve the growth of wheat. Bainong160 and Yanzhan4110 had a 4.78% and 2.66% increase in biomass, respectively. When the concentration of Pb increased to 800 mg·L^-1, wheat growth was inhibited. There were 25.66% and 38.60% decrease in biomass for Bainong160 and Yanzhan4110, respectively. In addition, there was a difference in root/shoot ratio between the two cultivars. When the concentration of Pb increased from 100 mg·L^-1 to 800 mg·L^-1, Bainong160 had no increase, but there was an increase from 0.71 to 0.81 in Yanzhan4110. After 4-week stress, the Pb contents of stems and leaves, and roots in Bainong160 were lower than those in Yanzhan4110. For subcellular distribution, Pb was mainly observed in the cell wall and cytoplasm, which accounted for 72%-86% of the total, in both wheat cultivars under different levels of Pb stress. When the concentration of Pb increased from 100 mg·L^-1 to 800 mg·L^-1, Yanzhan4110 had a 8% decrease in the proportion of the root cell wall and cytoplasm of Pb, and 4% decrease in this proportion stems and leaves, but the value for Bainong160 increased by 9% for root and 1% for stems and leaves. For chemical forms, poorly-soluble Pb lead (i.e. acetic acid and hydrochloric acid extractable) was mainly detected, which accounted for 67%-85% of the total. NaCl extractable Pb accounted for 6%-18% of the total, and the sum of ethanol extractable, deionized water extractable and residue Pb accounted for 8%-16%. In addition, the contents of active-Pb (i.e. ethanol and deionized water extractable) in roots of Bainong160 were lower than those in Yanzhan4110. The active-Pb in stems and leaves was different from that in roots. At the level of 100 mg·L^-1 Pb, the contents of active-Pb in stems and leaves of Bainong160 were lower than those in Yanzhan4110, when Pb increased to 800 mg L^-1, there was no difference in contents of active-Pb in stems and leaves between two cultivars.【Conclusion】Under Pb stress, root-surface of Bainong160 presented stronger resistance to Pb than Yanzhan4110. The cultivar had Pb fixation on the cell wall, which limits further transport of Pb and reduce the toxicity of Pb to shoots. For chemical forms, the distribution ratio of various forms of Pb is closely related to detoxification mechanism, but performances are not the same for different organs.