秦丽,
何永美,
王吉秀,
李博,
蒋明,
李元^,
云南农业大学资源与环境学院 昆明 650201
基金项目: 云南省重点研发计划项目2018BB017
云南省重点研发计划项目2019BC001-04
国家自然科学基金项目31560163
国家自然科学基金项目31860112
国家自然科学基金项目41761073
国家自然科学基金项目41967049
云南生物资源保护与利用国家重点实验室项目GZJS201902

详细信息

作者简介:秦丽, 主要研究方向为土壤重金属污染与修复。E-mail:qinli2975@ynau.edu.cn

通讯作者:李元, 主要研究方向为污染生态学与修复生态。E-mail:liyuan03@ynau.edu.cn

中图分类号:X503.231

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出版历程

收稿日期:2019-12-02
录用日期:2020-04-08
刊出日期:2020-06-01

Lead accumulation and low-molecular-weight organic acids secreted by roots in Sonchus asper L.-Zea mays L. intercropping system

QIN Li,
HE Yongmei,
WANG Jixiu,
LI Bo,
JIANG Ming,
LI Yuan^,
College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China
Funds: the Key Research and Development Project of Yunnan Province2018BB017
the Key Research and Development Project of Yunnan Province2019BC001-04
the National Natural Science Foundation of China31560163
the National Natural Science Foundation of China31860112
the National Natural Science Foundation of China41761073
the National Natural Science Foundation of China41967049
the Fund of the State Key Laboratory for Construction and Utilization of Bio-Resources in Yunnan of ChinaGZJS201902

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Corresponding author:LI Yuan, E-mail:liyuan03@ynau.edu.cn

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摘要
摘要:为探明间作作物根系分泌低分子量有机酸对土壤重金属生物有效性的影响，采用矿区周边农田土壤进行室内盆栽试验，研究了云南本土超累积植物续断菊（Sonchus asper L.Hill）和玉米（Zea mays L.）间作下，植物生长、根系低分子量有机酸分泌量、根际土壤Pb提取形态以及植物Pb积累特点。结果表明：与单作相比，间作续断菊地上部和根部生物量、根长、根内径和根系体积均显著增加（P < 0.05）；间作玉米根部生物量、根长、根内径和根系体积显著增加（P < 0.05）。柠檬酸、草酸是续断菊和玉米根系分泌的主要低分子量有机酸，间作导致续断菊根系低分子量有机酸的分泌量增加，玉米根系低分子量有机酸的分泌量降低。续断菊根际土壤生物有效态Pb含量增加85.2%（P < 0.05），而玉米根际土壤生物有效态Pb含量降低26.1%（P < 0.05）。续断菊体内Pb含量显著增加18.0%~43.2%（P < 0.05），富集系数提高26.0%，而转运系数降低42.0%；玉米地上部Pb含量显著降低24.3%（P < 0.05），转运系数降低43.1%。续断菊根系分泌的柠檬酸和草酸数量，均与土壤生物有效态Pb含量呈显著正相关，且土壤有效态Pb含量分别与续断菊地上部和根部的Pb含量呈显著正相关。表明间作增加了续断菊对Pb的吸收积累量，与间作体系植物根系分泌的低分子有机酸介导下的土壤有效态Pb含量增加密切相关。
关键词:Pb污染/
低分子量有机酸/
续断菊/
玉米/
间作
Abstract:There is a close relationship between low-molecular-weight organic acids (LMWOAs) secreted by plant roots and plant accumulation of heavy metals when intercropping accumulators and crops in heavy metal-contaminated soils. However, the specific mechanism behind this remains unclear. Sonchus asper L. Hill is a native hyper accumulator that can be found in Yunnan. Plant growth, amounts of LMWOAs secreted by plant roots, rhizosphere soil extractable lead (Pb) contents, and plant Pb accumulation characteristics were studied under S. asper-Zea mays L. intercropping in soil that was collected from a farmland surrounding a mining area, in order to investigate the effects of the LMWOAs produced by intercropping roots on heavy metal bioavailability in soils. The results showed that the aboveground and root biomass, root length, root inner diameter, and root volume of S. asper were significantly increased (P < 0.05), and that the root biomass, root length, root diameter, and root volume of Z. mays were significantly increased (P < 0.05) under the intercropping systems compared to under the monoculture systems. The major LMWOAs secreted by the roots of both S. asper and Z. mays were citric acid and oxalic acid. Intercropping resulted in an increase and decrease in the LMWOA contents secreted by S. asper and Z. mays roots, respectively. The bio-available Pb content in the rhizosphere soil of S. asper increased by 85.2% (P < 0.05), and that of Z. mays decreased by 26.1% (P < 0.05) under intercropping. The Pb content, enrichment factor, and transfer coefficient increased by 18.0%-43.2%, increased by 26.0%, and reduced by 42.0% in S. asper under intercropping, respectively. Compared to the monoculture system, the shoot Pb content and Pb transfer coefficient decreased by 24.3% and 43.1% (P < 0.05) in Z. mays under the intercropping system, respectively. The amounts of citric acid and oxalic acid secreted by S. asper roots were significantly positively correlated with the soil bio-available Pb content, and the bio-available Pb content in soil was significantly positively correlated with S. asper shoot and root Pb contents. The results indicate that intercropping increases the uptake and accumulation of Pb in S. asper. These are both closely correlated with increases in soil bio-available Pb, which is mediated by plant roots that secrete LMWOAs.
Key words:Pb pollution/
Low-molecular-weight organic acid/
Sonchus asper L. Hill/
Zea mays L./
Intercropping

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图1有机酸标准品色谱图
1:草酸; 2:酒石酸; 3:柠檬酸; 4:苹果酸; 5:乳酸; 6:乙酸; 7:马来酸; 8:琥珀酸。
Figure1.HPLC chromatogram of the mixed standard solution of 8 organic acids
1: oxalic acid; 2: tartaric acid; 3: citric acid; 4: malic acid; 5: lactic acid; 6: acetic acid; 7: maleic acid; 8: succinic acid.


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图2间作对续断菊(A)和玉米(B)根系分泌低分子量有机酸数量和种类的影响
图中数据为均值±标准误差(n=3)。*表示同一植物单作和间作处理间在P < 0.05水平差异显著。
Figure2.Contents and types of low-molecular-weight organic acids (LMWOA) in root exudates of Sonchus asper L. Hill (A) and Zea mays L. (B) under intercropping
All values are mean ± standard error (n = 3). * means significant difference between monoculture and intercropping of the same crop at P < 0.05 level.


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图3间作对续断菊(A)、玉米(B)根际土壤不同提取形态Pb含量的影响
A:可交换态; B:碳酸盐结合态; C:铁锰氧化物结合态; D:有机结合态; E:残渣态。图中数据为均值±标准误差(n=3)。*表示同一植物单作和间作间在P < 0.05水平差异显著。
Figure3.Contents of different extracted Pb forms in the rhizosphere soil of Sonchus asper L. Hill (A) and Zea mays L. (B) under intercropping
A: exchangeable related Pb; B: carbonate related Pb; C: ferric manganese oxidation related Pb; D: organic complexation Pb; E: residual Pb. All values are mean ± standard error (n = 3). * means significant difference between monoculture and intercropping of the same crop at P < 0.05 level.


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图4间作对续断菊(A)、玉米(B)不同部位Pb含量的影响
图中数据为均值±标准误差(n=3)。*表示同一植物单作和间作处理间在P < 0.05水平差异显著。
Figure4.Pb contents in different organs of Sonchus asper L. Hill (A) and Zea mays L. (B) under intercropping
All values are mean ± standard error (n = 3). * means significant difference between monoculture and intercropping of the same crop at P < 0.05 level.


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表1不同种植方式对续断菊和玉米生长和根系形态的影响
Table1.Effect of cropping patterns on the growth and root morphology of Sonchus asper L. Hill and Zea mays L.

植物 Plant	种植方式 Cropping pattern	生长形态Growth morphology				根系形态Root morphology				生物量Biomass (g·plant-1)
		株高 Plant height (cm)	叶片数 Number of blades	茎径/冠幅 Stem diameter or crown width (cm)		根长 Root length (cm)	根内径 Root inner diameter (cm)	根系体积 Root volume (mL)		地上 Shoot	根 Root
玉米Z. mays	单作Monoculture	126.4±17.9b	10.0±1.5a	1.28±0.07b		28.32±5.54a	0.73±0.06b	7.75±1.50b		8.93±0.96a	1.44±0.25b
	间作Intercropping	171.5±21.3a	12.0±1.1a	1.64±0.08a		32.80±6.60a	0.97±0.12a	12.25±3.20a		8.62±1.54a	1.98±0.17a
续断菊S. asper	单作Monoculture	11.58±1.06b	12.0±1.4b	19.56±5.93a		11.17±0.76b	0.93±0.15b	5.67±1.53b		0.80±0.09b	0.20±0.01b
	间作Intercropping	16.38±0.89a	17.0±0.9a	20.21±3.37a		17.33±1.61a	1.40±0.36a	7.01±1.00a		1.04±0.06a	0.27±0.02a
同列不同小写字母表示同一植物单作和间作在P < 0.05水平差异显著(Duncan法)。Different lowercase letters in the same column mean significant differences between monoculture and intercropping of the same crop at P < 0.05 leve1.

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表2间作对续断菊和玉米Pb累积特征的影响
Table2.Accumulation characteristics of Pb of Sonchus asper L. Hill and Zea mays L. under intercropping

种植方式 Planting pattern	续断菊S. asper				玉米Z. mays
	富集系数 Enrichment factor	转运系数 Transfer coefficient	有效转运系数 Effective transfer coefficient		富集系数 Enrichment factor	转运系数 Transfer coefficient	有效转运系数 Effective transfer coefficient
单作Monoculture	0.61	0.33	1.32		0.11	0.57	3.55
间作Intercropping	0.77	0.19	0.73		0.12	0.33	1.41

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表3续断菊和玉米间作系统植物Pb含量与土壤Pb形态的相关性分析
Table3.Correlations between contents of different Pb forms in rhizosphere soil and plant Pb contents of Sonchus asper L. Hill and Zea mays L. intercropping system

植物Plant	部分Part	A	B	A+B	C	D	E
续断菊 S. asper	地上Shoot	0.926**	0.862*	0.934**	-0.858*	-0.893*	0.187
	根Root	0.975**	0.922**	0.853*	-0.840*	0.754	-0.140
玉米 Z. mays	茎Stem	0.832*	-0.832*	0.964**	0.883*	-0.715	0.674
	叶Leaf	-0.875*	0.809	-0.828*	-0.869*	0.702	0.674
	籽粒Grain	0.259	-0.024	-0.118	0.516	-0.149	-0.009
	根Root	0.960**	-0.789	-0.917*	0.899*	-0.880*	0.501
*: P < 0.05; **: P < 0.01. A:可交换态Pb; B:碳酸盐结合态Pb; C:铁锰氧化物结合态Pb; D:有机结合态Pb; E:残渣态Pb。A: exchangeable related Pb; B: carbonate related Pb; C: ferric manganese oxidation related Pb; D: organic complexation Pb; E: residuals Pb.

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表4续断菊和玉米间作系统根系分泌有机酸与土壤Pb形态的相关性分析
Table4.Correlations between contents of different Pb forms in the rhizosphere soil and contents of organic acids in root exudates of Sonchus asper L. Hill and Zea mays L. intercropping system

	续断菊S. asper						玉米Z. mays
	A	B	C	D	E		A	B	C	D	E
草酸Oxalic acid	0.936**	0.759	-0.899*	-0.229	0.786		0.948**	-0.196	-0.692	-0.812*	-0.901*
柠檬酸Citric acid	0.969**	0.875*	-0.908*	-0.414	0.921**		0.955**	-0.619	-0.512	-0.723	-0.759
*: P < 0.05; **: P < 0.01. A:可交换态Pb; B:碳酸盐结合态Pb; C:铁锰氧化物结合态Pb; D:有机结合态Pb; E:残渣态Pb。A: exchangeable related Pb; B: carbonate related Pb; C: ferric manganese oxidation related Pb; D: organic complexation Pb; E: residuals Pb.

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表5土壤可交换态Pb含量(X)与续断菊地上部和根Pb吸收量(Y)的逐步回归分析结果
Table5.Step regression analysis of content of exchangeable related Pb in soil (X) to amounts of Pb absorbed by shoot or root Sonchus asper L. Hill (Y)

	逐步回归方程Stepwise regression equation	R	t	P
地上Shoot	Y=1.436X+71.695	0.926	4.901	0.008
根Root	Y=11.665X+147.460	0.975	0.711	0.001

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