Effects of Lead on Plant Growth, Lead Accumulation and Phytochelatin Contents of Hydroponically-Grown <i>Sesbania </i><i>E</i><i>xaltata</i>

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 technology depends 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 to lead (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.

Evaluation of Lead Tolerant Plant Growth Promoting Rhizobacteria for Plant Growth and Phytoremediation in Lead Contamination

“…Our results showed a reduction in the growth and physiology of sunflower in lead contamination as compared to plants grown in uninoculated treatment without contamination. These findings are similar to those of Hussain et al (2006Hussain et al ( , 2013 and McComb et al (2012). It is known that the reduction in plant growth by lead contamination might be due to its interference with the uptake of nutrients, respiration, photosynthetic rate and cell membrane permeability (Sharma and Dubey 2005).…”

Seed priming with KNO3 mediates biochemical processes to inhibit lead toxicity in maize (Zea mays L.)

“…a) might be the result of direct exposure of roots to Pb toxicity which also resulted in more pronounced activities of antioxidant enzymes in roots. An elevation in activities of antioxidative enzymes in response to Pb induced oxidative stress is well reported in literature . These enzymes serve as a prime defence strategy against radical O 2− , OH − , H 2 O 2 and conjugate dienes to prevent lipid peroxidation mediated degradation of membranes .…”

Removal of Lead and Chromium from Synthetic Wastewater Using Vetiveria zizanioides

“…This might be responsible for the increase in Pb uptake with increase in Pb concentration in the present study. Many recent studies have also reported an increase in the GSH concentration with an increase in heavy metal stress due to Pb [28][29][30][31][32][33]. However, at higher concentrations of Pb, the toxicity effects also increased and reduced the Pb uptake [27].…”