Absorcion Plomo

World Environment 2012, 2(3): 38-43
DOI: 10.5923/j.env.20120203.04

Effects of Lead on Plant Growth, Lead Accumulation and
Phytochelatin Contents of Hydroponically-Grown
Sesbania Exaltata
Jacqueline McComb, Sonya Hentz, Gloria S. Miller*, Maria Begonia, Gregorio Begonia
Plant Physiology/Microbiology Laboratory, Department of Biology, P.O. Box 18540, College of Science, Engineering andTechnology,
Jackson State University, 100 Lynch Street, Jackson, Mississippi, 39217, USA

Abstract Phytoremediation is the use of living plants for the removal of contaminants from soil, water, sediments, and air.
Soil contamination by heavy metals (HMs) is an important environmental concern. The success of phytoextraction, a subset
of phytoremediation, as an environment clean-up technologydepends on several factors including the extent of soil contamination and the bioavailability of the metal. The aim of phytoextraction research is to identify metal-tolerant plants that
are capable of uptake and efficient translocation of HMs to harvestable above-ground organs. The main objective of this
study was to assess the metal tolerance of coffeeweed (Sesbania exaltata Raf.) after exposure tolead (Pb) solutions. Sesbania
plants were grown for 30 days at the Jackson State University greenhouse prior to exposure to different concentrations (0, 0.1,
1.0, 5.0, 10.0, 20.0 μM Pb) of lead nitrate. Four 30-day old seedlings were grown hydroponically in each designated 15-mL
cup containing the Pb treatments. Plants were harvested after various exposure periods (0, 2, 5, 8, 12, 15 days).Morphological characteristics were evaluated, and lead contents were quantified by Inductively Coupled Plasma - Optical Emission
Spectrometry (ICP-OES). Phytochelatin synthesis was determined indirectly by quantifying the acid - thiol contents of roots
and shoots. Our results indicated that lead tissue uptake increased with increasing concentrations of lead (i.e. 20.0 μM versus
1.0 μM). However,plant roots and shoots displayed symptoms of toxicity as evidenced by their decreased biomass with
increasing concentrations of lead. Also, plants exposed to higher Pb concentrations exhibited mild chlorosis. Overall, Sesbania was relatively tolerant to lead. Although acid - soluble thiol contents appeared to correlate with Pb uptake especially at
higher concentrations of Pb treatments,phytochelatin synthesis as a metal-tolerance mechanism in Sesbania is inconclusive
at this time. Further experiments are warranted to elucidate whether such tolerance mechanism exists in Sesbania.
Keywords Lead, Phytoremediation, Sesbania Exaltata

1. Introduction
Since the Industrial Revolution, mankind has been introducing various toxic pollutants into the environment at an
alarming rate[1, 2].These pollutants are a cocktail of various organic compounds and heavy metals (HMs) which can
drastically affect human and animal health and ecosystems[3]. Heavy metals such as lead (Pb) are of major concern because of their persistence in the environment[4].
Lead is a toxic pollutant mainly introduced into the environment through smelting processes[5]. Although Pb has no
known functions inbiological systems, it can impact the
central nervous system especially in children leading to
reduced growth of the brain[6]. It is generally ranked the
number one heavy metal pollutant and number two of all
* Corresponding author:
gloria.s.miller@jsums.edu (Gloria S. Miller)
Published online at http://journal.sapub.org/env
Copyright © 2012 Scientific & Academic Publishing. All Rights Reservedhazardous substances by the Agency for Toxic Substances
and Disease Registry[7, 8].
Cognizant of their effects on human and animal health
and ecosystems, it is imperative to reduce the concentrations of HMs such as Pb from contaminated soil and water
sources. Numerous engineering-based technologies have
been used to remediate metal-contaminated soils and
aquatic systems but they are very...