Sorghum roots are inefficient in uptake of EDTA-chelated lead

Yong Xu, Naoki Yamaji, Renfang Shen, Jian Feng Ma

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

• Background and Aims: Ethylene diamine tetraacetic acid (EDTA)-assisted phytoremediation has been developed to clean up lead (Pb)-contaminated soil; however, the mechanism responsible for the uptake of EDTA-Pb complex is not well understood. In this study, the accumulation process of Pb from EDTA-Pb is characterized in comparison to ionic Pb [Pb(NO 3)2] in sorghum (Sorghum bicolor). • Methods: Sorghum seedlings were exposed to a 0.5 mm CaCl2 (pH 5.0) solution containing 0, 1 mm Pb(NO3)2 or EDTA-Pb complexes at a molar ratio of 1:0.5, 1:1, 1:2 and 1:4 (Pb:EDTA). The root elongation of sorghum at different ratios of Pb:EDTA was measured. Xylem sap was collected after the stem was severed at different times. The concentration of Pb in the shoots and roots were determined by an atomic absorption spectrometer. In addition, the roots were stained with Fluostain I for observation of the root structure. • Key Results: Lead accumulation in the shoots of the plants exposed to EDTA-Pb at 1:1 ratio was only one-fifth of that exposed to ionic Pb at the same concentration. Lead accumulation decreased when transpiration was suppressed. The concentration of Pb in the xylem sap from the EDTA-Pb-treated plants was about 1/25 000 of that in the external solution. Root elongation was severely inhibited by ionic Pb, but not by EDTA-Pb at a 1:1 ratio. Root staining showed that a physiological barrier was damaged in the roots exposed to ionic Pb, but not in the roots exposed to EDTA-Pb. • Conclusions: All these results suggest that sorghum roots are inefficient in uptake of EDTA-chelated Pb and that enhanced Pb accumulation from ionic Pb was attributed to the damaged structure of the roots.

Original languageEnglish
Pages (from-to)869-875
Number of pages7
JournalAnnals of Botany
Volume99
Issue number5
DOIs
Publication statusPublished - May 2007

Fingerprint

diamines
Sorghum (Poaceae)
ethylene
uptake mechanisms
acids
sap
xylem
root growth
shoots
phytoremediation
spectrometers
Sorghum bicolor
polluted soils
transpiration

Keywords

  • Complex
  • EDTA
  • Form
  • Pb
  • Phytoremediation
  • Sorghum (Sorghum bicolor)
  • Uptake system

ASJC Scopus subject areas

  • Horticulture
  • Plant Science

Cite this

Sorghum roots are inefficient in uptake of EDTA-chelated lead. / Xu, Yong; Yamaji, Naoki; Shen, Renfang; Ma, Jian Feng.

In: Annals of Botany, Vol. 99, No. 5, 05.2007, p. 869-875.

Research output: Contribution to journalArticle

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title = "Sorghum roots are inefficient in uptake of EDTA-chelated lead",
abstract = "• Background and Aims: Ethylene diamine tetraacetic acid (EDTA)-assisted phytoremediation has been developed to clean up lead (Pb)-contaminated soil; however, the mechanism responsible for the uptake of EDTA-Pb complex is not well understood. In this study, the accumulation process of Pb from EDTA-Pb is characterized in comparison to ionic Pb [Pb(NO 3)2] in sorghum (Sorghum bicolor). • Methods: Sorghum seedlings were exposed to a 0.5 mm CaCl2 (pH 5.0) solution containing 0, 1 mm Pb(NO3)2 or EDTA-Pb complexes at a molar ratio of 1:0.5, 1:1, 1:2 and 1:4 (Pb:EDTA). The root elongation of sorghum at different ratios of Pb:EDTA was measured. Xylem sap was collected after the stem was severed at different times. The concentration of Pb in the shoots and roots were determined by an atomic absorption spectrometer. In addition, the roots were stained with Fluostain I for observation of the root structure. • Key Results: Lead accumulation in the shoots of the plants exposed to EDTA-Pb at 1:1 ratio was only one-fifth of that exposed to ionic Pb at the same concentration. Lead accumulation decreased when transpiration was suppressed. The concentration of Pb in the xylem sap from the EDTA-Pb-treated plants was about 1/25 000 of that in the external solution. Root elongation was severely inhibited by ionic Pb, but not by EDTA-Pb at a 1:1 ratio. Root staining showed that a physiological barrier was damaged in the roots exposed to ionic Pb, but not in the roots exposed to EDTA-Pb. • Conclusions: All these results suggest that sorghum roots are inefficient in uptake of EDTA-chelated Pb and that enhanced Pb accumulation from ionic Pb was attributed to the damaged structure of the roots.",
keywords = "Complex, EDTA, Form, Pb, Phytoremediation, Sorghum (Sorghum bicolor), Uptake system",
author = "Yong Xu and Naoki Yamaji and Renfang Shen and Ma, {Jian Feng}",
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language = "English",
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T1 - Sorghum roots are inefficient in uptake of EDTA-chelated lead

AU - Xu, Yong

AU - Yamaji, Naoki

AU - Shen, Renfang

AU - Ma, Jian Feng

PY - 2007/5

Y1 - 2007/5

N2 - • Background and Aims: Ethylene diamine tetraacetic acid (EDTA)-assisted phytoremediation has been developed to clean up lead (Pb)-contaminated soil; however, the mechanism responsible for the uptake of EDTA-Pb complex is not well understood. In this study, the accumulation process of Pb from EDTA-Pb is characterized in comparison to ionic Pb [Pb(NO 3)2] in sorghum (Sorghum bicolor). • Methods: Sorghum seedlings were exposed to a 0.5 mm CaCl2 (pH 5.0) solution containing 0, 1 mm Pb(NO3)2 or EDTA-Pb complexes at a molar ratio of 1:0.5, 1:1, 1:2 and 1:4 (Pb:EDTA). The root elongation of sorghum at different ratios of Pb:EDTA was measured. Xylem sap was collected after the stem was severed at different times. The concentration of Pb in the shoots and roots were determined by an atomic absorption spectrometer. In addition, the roots were stained with Fluostain I for observation of the root structure. • Key Results: Lead accumulation in the shoots of the plants exposed to EDTA-Pb at 1:1 ratio was only one-fifth of that exposed to ionic Pb at the same concentration. Lead accumulation decreased when transpiration was suppressed. The concentration of Pb in the xylem sap from the EDTA-Pb-treated plants was about 1/25 000 of that in the external solution. Root elongation was severely inhibited by ionic Pb, but not by EDTA-Pb at a 1:1 ratio. Root staining showed that a physiological barrier was damaged in the roots exposed to ionic Pb, but not in the roots exposed to EDTA-Pb. • Conclusions: All these results suggest that sorghum roots are inefficient in uptake of EDTA-chelated Pb and that enhanced Pb accumulation from ionic Pb was attributed to the damaged structure of the roots.

AB - • Background and Aims: Ethylene diamine tetraacetic acid (EDTA)-assisted phytoremediation has been developed to clean up lead (Pb)-contaminated soil; however, the mechanism responsible for the uptake of EDTA-Pb complex is not well understood. In this study, the accumulation process of Pb from EDTA-Pb is characterized in comparison to ionic Pb [Pb(NO 3)2] in sorghum (Sorghum bicolor). • Methods: Sorghum seedlings were exposed to a 0.5 mm CaCl2 (pH 5.0) solution containing 0, 1 mm Pb(NO3)2 or EDTA-Pb complexes at a molar ratio of 1:0.5, 1:1, 1:2 and 1:4 (Pb:EDTA). The root elongation of sorghum at different ratios of Pb:EDTA was measured. Xylem sap was collected after the stem was severed at different times. The concentration of Pb in the shoots and roots were determined by an atomic absorption spectrometer. In addition, the roots were stained with Fluostain I for observation of the root structure. • Key Results: Lead accumulation in the shoots of the plants exposed to EDTA-Pb at 1:1 ratio was only one-fifth of that exposed to ionic Pb at the same concentration. Lead accumulation decreased when transpiration was suppressed. The concentration of Pb in the xylem sap from the EDTA-Pb-treated plants was about 1/25 000 of that in the external solution. Root elongation was severely inhibited by ionic Pb, but not by EDTA-Pb at a 1:1 ratio. Root staining showed that a physiological barrier was damaged in the roots exposed to ionic Pb, but not in the roots exposed to EDTA-Pb. • Conclusions: All these results suggest that sorghum roots are inefficient in uptake of EDTA-chelated Pb and that enhanced Pb accumulation from ionic Pb was attributed to the damaged structure of the roots.

KW - Complex

KW - EDTA

KW - Form

KW - Pb

KW - Phytoremediation

KW - Sorghum (Sorghum bicolor)

KW - Uptake system

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JO - Annals of Botany

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