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.

Cadmium (Cd) contamination of the environment is a major concern because of its impact on human health, food supply chain, and ecosystems. Phytoremediation has emerged as an alternative technology to expensive engineering techniques. The objectives of this research were to evaluate the growth and cadmium uptake of wheat (Triticum aestivum L. cv TAM 109) plants exposed to Cd at different periods; and assess whether phytochelatin (PC) synthesis can explain the wheat's tolerance mechanism to cadmium. Wheat seeds were grown in sand medium for 30 days (pre-metal treatment). After initial exposure to different Cd concentrations using hydroponic systems, plants were harvested at different day intervals, separated into roots and shoots, dried at 75℃ for 2 days, weighed for dry biomass, and acid-digested for cadmium uptake determinations. Cadmium uptake and PC contents of roots and shoots were quantified using established procedures. Results showed that shoot and root biomass increased with exposure time, and was more pronounced in the shoot than in the roots. Shoot Cd uptake increased with increasing Cd concentrations, except at days 8, 12, and 15 wherein Cd uptake was very minimal especially at 20 µM. Root Cd uptake increased with increasing exposure periods and Cd concentrations. The syntheses of PC in shoots were significantly enhanced only at 20 µM Cd. There were no significant differences in quantity of roots' PC regardless of Cd treatments.