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Lead uptake and its effect on plant growth and photosynthesis of piper sarmentosum (wild pepper) and epipremnum aureum (money plant)
Author
Cross, Sharon Reena
Supervisor
He, Jie
Abstract
In the present study, two common local landscaping plants, Piper sarmentosum (wild pepper) and Epipremnum aureum (money plants) were used to study the uptake of Pb. The fresh weight and dry weights of the roots and shoots of both plant species was monitored during the treatment period. All the Pb treated plants continued to grow in the presence of Pb, although the growth was much slower as compared to the control plants. It was also found that shoot growth was affected more than root growth in the wild pepper plants whilst the reverse was true for the money plants. The results of the present study also found that the Pb concentration in the leaves, stems and roots for both plant species increased significantly with increasing Pb concentration and prolonged treatment time. The order of accumulation appeared to be roots>stems>leaves in wild pepper plants and roots> aerial roots>stems> leaves in money plants. Visible symptoms of toxicity such as yellowing of leaves and wilting, as well as significant reductions in photosynthetic light use of efficiency occurred only from week 8 in both plant species. Changes in Chl content were also measured and indicate that although both plant species were affected by the Pb treatment, they were tolerant to Pb stress. The reduction in photosynthetic CO2 assimilation rate (A) occurred much earlier than the changes in the Fv/Fm ratios for both plant species. However, the decrease in A was not due to stomatal limitation (gs) as there were no significant differences in gs in all the plants. Water deficit was experienced in wild pepper plants only after 7 weeks of treatment and only in the highest treatment whilst in money plants, there was no significant changes in the water potential of the plants. Both wild pepper and money plants were tolerant to Pb stress based on their photosynthetic capacities. From studies of the leachate collected after Pb treatment was stopped, it was found that the concentration of Pb in the wild pepper plants was lower than that for the money plants in all the Pb treated plants by week 3. Analysis of the Pb content retained in the tissues of both plant species indicate that the wild pepper plants were able to retain more Pb in their roots whilst the money plants were able to retain more Pb in their aerial tissues. Both plant species have leaves with large surface areas, extensive root systems and are able to propagate fast. These features make them potential candidates for phytoremediation of Pb from contaminated soils. Comparisons between the two plant species based on the various parameters studied indicate that money plant is a better candidate for phytoremediation as it is more tolerant to photosynthetic stress due to action of Pb and it is able to retain higher amounts of Pb in its various plant tissues. In addition, it possesses numerous aerial roots which are capable of accumulating significant amounts of Pb.
Date Issued
2010
Call Number
QK753.H4 Cro
Date Submitted
2010