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土壤重金属污染已成为当前亟须解决的重大环境问题[1-3]。中国大部分区域土壤目前正在面临严重的污染问题,近1/5的耕地受到影响,其中铅锌铜镉等4种重金属污染占全部污染土地面积的70%以上。土壤重金属污染不仅导致土地生产力下降,也使得重金属元素进入食物链,严重危害人类健康。铅为最重要的土壤重金属污染元素之一[4]。针对土壤铅污染,植物修复是一种非常重要的技术手段,而修复植物选择则是其中的关键。近年来,有关铅污染条件下植物修复的研究报道颇多[5-12],但主要集中于草本,如蜈蚣草Nephrolepis auriculata,堇菜Viola verecunda,狗牙根Cynodon dactylon,早熟禾Poa annua等[13-16]。草本的生物量较小,根系分布较浅,对重金属吸收效果存在一定的局限性。因此,筛选对重金属污染耐性强、富集能力与固定能力强、生物量大的树种,实现对重金属污染物的快速吸收与转移成了植物修复重金属污染的新方向与新亮点。本研究以刺槐Robinia pseudoacacia的幼苗生长及铅离子转运特性为对象,研究刺槐对铅胁迫的耐性程度,通过离子吸收转运,了解刺槐对铅胁迫的耐受机制,为铅污染耐受性树种选择奠定理论基础。
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由图 1A可知:在250 mg·L-1铅处理下,刺槐幼苗的地径比对照植株地径增加了2.7%,但差异不显著(P>0.05)。随着铅质量浓度的增加,刺槐幼苗的地径逐步降低,在1 500 mg·L-1处理下,其幼苗地径最小。
图 1 铅胁迫对刺槐幼苗生长性状地径(A),苗高(B),鲜质量(C)和干质量(D)的影
Figure 1. Effect of Pb stress on growth characteristics including diameter (A), seedling height (B), fresh weight (C), dry weight (D) of Robinia pseudoacacia seedlings
由图 1B可知:250 mg·L-1铅处理的刺槐幼苗的茎高比对照植株增加了2.2%,但差异不显著(P>0.05)。其他处理下刺槐幼苗的茎高均低于对照,但差异不显著(P>0.05),其中在500 mg·L-1处理的幼苗茎高最小,分别比对照与250 mg·L-1处理低14.0%和15.8%。
250 mg·L-1铅处理的刺槐幼苗鲜质量值最高,比对照植株增加了2.6%,但差异不显著(P>0.05,图 1C)。随着处理质量浓度的增加,刺槐幼苗鲜质量大体呈降低趋势,但各处理间差异不显著(P>0.05),其中在500 mg·L-1处理的幼苗鲜质量值最小,分别比对照与250 mg·L-1处理低17.6%和19.7%。
随着铅处理质量浓度的增加,幼苗干物质质量呈现递减趋势,各处理之间差异不显著(P>0.05),其中1 000 mg·L-1处理的干物质质量最小,低于对照值23.60%(图 1D)。
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由图 2可知:随铅质量浓度的上升,铅在根中的质量分数逐渐增加,在中低质量浓度(≤500 mg·L-1)时,根部铅离子质量分数增加幅度较小,处理间差异不显著(P>0.05);当铅质量浓度大于500 mg·L-1时,铅在根部的质量分数显著增加(P<0.05),尤其在1 000和1 500 mg·L-1时,幼苗根系中铅质量分数分别达到70.81和93.28 μg·g-1。随着铅处理质量浓度上升,刺槐幼苗茎部铅质量分数呈现单峰曲线,先上升后下降;各相邻处理间差异较大,变化显著(P<0.05),且在500 mg·L-1处理中幼苗茎部的铅质量分数最高(39.42 μg·g-1)。各处理幼苗叶片的铅质量分数均低于对照植株,但差异均不显著(P>0.05)。
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根据图 3A可知:随铅胁迫质量浓度的升高,各处理植株的叶/茎离子转运率急剧下降,均显著低于对照值(P<0.05);在各试验处理中,500 mg·L-1处理植株的叶/茎离子转运率显著低于其他处理(P<0.05),其他处理之间差异不显著(P>0.05)。
图 3 铅胁迫对刺槐幼苗根、茎、叶间铅离子转运率的影响
Figure 3. Effect of Pb stress on Pb ion transfer ratio between root, stem and leaf of Robinia pseudoacacia seedlings
在中低质量浓度(≤500 mg·L-1)时,随胁迫质量浓度的升高,幼苗的茎/根离子转运率显著上升(P<0.05);当铅质量浓度大于500 mg·L-1时,随铅质量浓度的增大,离子转运率逐渐降低,其中1 000,1 500 mg·L-1处理的植株茎/根离子转运率显著低于500 mg·L-1处理(P<0.05),但两处理之间差异不显著(P>0.05)(图 3B)。
与茎/根离子转运相似,随着铅处理质量浓度增加,幼苗的(叶+茎)/根离子转运率在中低质量浓度(≤500 mg·L-1)阶段急剧升高,250,500 mg·L-1两处理的离子转运率均显著高于对照值(P<0.05);随铅处理质量浓度进一步增大,幼苗(叶+茎)/根离子转运率急剧降低,显著低于500 mg·L-1处理值与对照值(P<0.05),但高质量浓度处理之间差异不显著(P>0.05)(图 3C)。
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在刺槐幼苗干质量、地径及苗高与幼苗根铅离子质量分数、茎铅离子质量分数、叶铅离子质量分数、根茎转运率、茎叶转运率、地上地下转运率之间进行相关分析。从表 1可以看出:铅胁迫幼苗生长与植物组织铅质量分数、铅离子转运特性存在相关性。幼苗干物质质量与根系铅离子质量分数、叶铅离子质量分数及茎叶转运呈显著性相关(P<0.05)或极显著性相关(P<0.01);幼苗地径生长与根系铅离子质量分数、叶铅离子质量分数、茎叶转运及(叶+茎)/根离子转运(地上地下转运)呈显著性相关(P<0.05);苗高生长仅与叶铅离子质量分数呈显著性相关(P<0.05),可能与叶片铅离子影响生长素形成,进而影响细胞延长,限制苗高生长有关。
表 1 铅胁迫条件下刺槐幼苗干质量、地径及苗高与幼苗根铅离子质量分数、茎铅离子质量分数、叶铅离子质量分数、根茎转运率、茎叶转运率、地上地下转运率之间的皮尔逊指数
Table 1. Pearson correlation of dry weight, stem diameter and height, respectively, to Pb ion contens of root, stem and leaf and Pb ion transfer ratios of root to stem, stem to leave, and root to both stem and leaf in Robinia pseudoacacia seedlings under Pb stress
性状 根铅离子质量分数 茎铅离子质量分数 叶铅离子质量分数 根茎转运 茎叶转运 地上地下转运 干质量 -0.452* -0.030 0.792** 0.105 0.593** 0.224 地径 -0.536* -0.081 0.594* 0.246 0.482* 0.462* 苗高 -0.080 -0.216 0.547* 0.029 0.307 0.193 说明:*与**分别表示显著相关(P<0.05)和极显著相关(P<0.01) -
幼苗干物质是植株生物量积累最直接的指标,也是植物生理功能的最佳体现;幼苗高生长与地径生长直接反应植株纵向与横向发育的状况,体现出植物细胞延长生长与分裂的能力。同时,刺槐幼苗上述3个生长指标分别受幼苗根铅离子质量分数、茎铅离子质量分数、叶铅离子质量分数、根茎转运率、茎叶转运率、地上地下转运率等6个指标影响。为了评估各因素对铅胁迫条件下刺槐幼苗生长的影响程度,就对幼苗干质量、苗高、地径与上述6个指标分别进行多元回归分析。然后,根据各指标标准回归系数的绝对值来比较其对铅胁迫植株的影响程度。
由表 2可发现:对刺槐幼苗的生物量积累影响最大的因素为根系铅质量分数,次之为叶片铅质量分数,茎部铅离子质量分数影响最小。同时,从组织的铅离子转运、分配来说,地上地下转运对植物干物质积累影响最大,茎叶转运次之,而根茎间的铅离子转运影响最小。
表 2 铅胁迫下刺槐幼苗干质量、苗高与地径和幼苗根铅离子质量分数等6个特征指标之间的多元回归分析
Table 2. Multiple regression analysis of dry weight, height and stem diameter in relation to six parameters of contents and tansfer ratios of lead ion in Robinia pseudoacacia seedlings under Pb stress
回归模型 F值 显著性 标准回归系数 b1 b2 b3 b4 b5 b6 y1=0.061+0.00lx1+0.00lx2+0.006x3-0.007x40.056x5+0.015x6,R2=0.983 77.689 0.000 1.52 0.091 0.287 -0.760 1.213 2.237 y2=1.038+0.0lx1+0.023x2+0.06lx3+1.22x4+0.027x5-0.022x6,R2=0.972 45.924 0.000 0.241 2.331 0.644 3.352 0.140 0.784 y3=0.878+0.09x1-0.027x2+0.056x3+0.085x4+1.96x5+0.06x6,R2=0.968 40.793 0.000 0.605 -1.761 0.381 1.482 0.645 1.382 说明:y1为幼苗干质量,y1为地径,y1为苗高;x1,x2,x3,x4,x5和x6分别代表幼苗根铅离子质量分数、茎铅离子质量分数、叶铅离子质量分数、根茎转运率、茎叶转运率、地上地下转运率;b1,b2,b3,b4,b5,b6是x1,x2,x3,x4,x5,x6的标准回归系数。 影响刺槐幼苗地径生长的最大因素是茎部铅离子质量分数,次之为叶片铅质量分数,影响最小的根系铅质量分数。此外,根茎间铅离子转运对幼苗横向生长影响最大,地上地下转运次之,而茎叶转运影响最小。
对刺槐幼苗高生长产生影响的最大因素是茎部铅离子质量分数,根系铅质量分数为次要因素,叶片铅质量分数影响最小。此外,根茎间铅离子转运对幼苗高生长影响最大,次要因素为地上地下转运,而茎叶转运对苗高生长影响最小。
Growth and ion transport with Pb stress in Robinia pseudoacacia seedlings
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摘要: 为了解刺槐Robinia pseudoacacia对铅胁迫的耐受程度与耐受机制,以刺槐幼苗为研究对象,用硝酸铅溶液浇灌处理,研究幼苗的生长特性、组织铅离子质量分数(μg·g-1)及离子转运特征。结果表明:250 mg·L-1铅处理对刺槐幼苗的茎高、地径、干质量、鲜质量等有一定的促进作用;在中高铅离子质量浓度(≥500 mg·L-1)下,刺槐幼苗的生长受到抑制。随着铅处理质量浓度的增加,幼苗根系铅离子质量分数显著上升(P < 0.05);茎部铅质量分数先升后降;叶中铅质量分数大体呈现降低趋势;叶/茎离子转运率急剧下降(P < 0.05);(叶+茎)/根、茎/根离子转运率先升后降。通过多元回归分析,发现根系铅质量分数、(叶+茎)/根离子转运对幼苗干物质积累影响最大;茎部铅离子质量分数、根茎间铅离子转运对幼苗地径、苗高生长影响最大。
图 3 表 2 参23 Abstract: To explore Robinia pseudoacacia (Black Locust) tolerance and mechanism to lead(Pb) stress, R. pseudoacacia seedlings were first watered with solutions of Pb(NO3)2 dissolved in distilled water. Then, properties of growth, lead concentration(μg·g-1), and ion transfer in stressed seedlings were analyzed using multivariate linear regression analysis, Ducan multiple comparison and single factor test design with treatments of 250, 500, 1 000 and 1 500 mg·L-1 and 3 replications. Experimental results showed that 250 mg·L-1 of Pb(NO3)2 solution slightly promoted height, stem diameter, and seedling dry and fresh weights, but these decreased when lead concentration was subsequently increased. Lead content significantly increased (P < 0.05) with accumulation found in roots; seedling stems showed a lead increase(P < 0.05) and a subsequent decrease (P < 0.05). In stressed seedlings leaf concentration declined in these treatments of 250 to 1 500 mg·L-1. In addition, the lead ion transfer-ratio for stem to leaf significantly declined (P < 0.05). However, as lead concentration increased, the root to stem and root to both stem and leaf concentration increased (P < 0.05) and then decreased (P < 0.05). The multivariate linear regression analysis, showed that the most important factors affecting accumulation of dry biomass were 1) lead concentration in roots and 2) ion transfer ratio of root to both stem and leaf. Also in stressed seedlings lead concentration in stems and ion transfer ratio of root to stem the most significantly affected (P < 0.05) growth of height and of stem diameter. It was drawn that lead accumulation in root and inhibition of its transfer could prevent leaves from damage deriving from lead stress, and they would be the tolerance mechanism to lead stress for Robinia pseudoacacia seedlings.[Ch,3 fig. 2 tab. 23 ref. ]-
Key words:
- botany /
- lead(Pb) stress /
- Robinia pseudoacacia /
- seedling /
- growth /
- ion transport
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表 1 铅胁迫条件下刺槐幼苗干质量、地径及苗高与幼苗根铅离子质量分数、茎铅离子质量分数、叶铅离子质量分数、根茎转运率、茎叶转运率、地上地下转运率之间的皮尔逊指数
Table 1. Pearson correlation of dry weight, stem diameter and height, respectively, to Pb ion contens of root, stem and leaf and Pb ion transfer ratios of root to stem, stem to leave, and root to both stem and leaf in Robinia pseudoacacia seedlings under Pb stress
性状 根铅离子质量分数 茎铅离子质量分数 叶铅离子质量分数 根茎转运 茎叶转运 地上地下转运 干质量 -0.452* -0.030 0.792** 0.105 0.593** 0.224 地径 -0.536* -0.081 0.594* 0.246 0.482* 0.462* 苗高 -0.080 -0.216 0.547* 0.029 0.307 0.193 说明:*与**分别表示显著相关(P<0.05)和极显著相关(P<0.01) 表 2 铅胁迫下刺槐幼苗干质量、苗高与地径和幼苗根铅离子质量分数等6个特征指标之间的多元回归分析
Table 2. Multiple regression analysis of dry weight, height and stem diameter in relation to six parameters of contents and tansfer ratios of lead ion in Robinia pseudoacacia seedlings under Pb stress
回归模型 F值 显著性 标准回归系数 b1 b2 b3 b4 b5 b6 y1=0.061+0.00lx1+0.00lx2+0.006x3-0.007x40.056x5+0.015x6,R2=0.983 77.689 0.000 1.52 0.091 0.287 -0.760 1.213 2.237 y2=1.038+0.0lx1+0.023x2+0.06lx3+1.22x4+0.027x5-0.022x6,R2=0.972 45.924 0.000 0.241 2.331 0.644 3.352 0.140 0.784 y3=0.878+0.09x1-0.027x2+0.056x3+0.085x4+1.96x5+0.06x6,R2=0.968 40.793 0.000 0.605 -1.761 0.381 1.482 0.645 1.382 说明:y1为幼苗干质量,y1为地径,y1为苗高;x1,x2,x3,x4,x5和x6分别代表幼苗根铅离子质量分数、茎铅离子质量分数、叶铅离子质量分数、根茎转运率、茎叶转运率、地上地下转运率;b1,b2,b3,b4,b5,b6是x1,x2,x3,x4,x5,x6的标准回归系数。 -
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https://zlxb.zafu.edu.cn/article/doi/10.11833/j.issn.2095-0756.2016.05.003