Accumulation of zinc by alternanthera sessilis

Abstract

Zinc is an essential element that contribute to plant growth and developmental processes and induces tolerance mechanism to adapt the external environment. However, excess amount of zinc in soil become pollutant to the environment. In Malaysia, especially in Johor, zinc accumulation is one of the major problems as soil contaminant cause long term effect to the environment. Fortunately, there are plants that could tolerate and accumulate high amount of zinc from soil known as zinc hyperaccumulators. Alternanthera sessilis is known as a hyperaccumulator for chromium and potential hyperaccumulator for zinc. This study was carried out to determine the ability of A. sessilis in up taking different zinc concentrations (0 ppm, 50 ppm, 100 ppm, 200 ppm and 300 ppm) and the compartmentalization of zinc in different parts of the plant. Overall growth of A. sessilis at different zinc concentrations were observed and analysed by statistical analysis to determine morphological changes in plant growth. Plant samples were extracted by acid digestion method and analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis to determine zinc concentrations in each part of the plant sample. The result of this study indicates that A. sessilis morphological growth and development was established as common growth phases from vegetative stage to branching stage with an estimation of two months and 15 days is suitable transfer to zinc treated soil. A. sessilis shows healthier growth in terms of new leaves, branches, height of the plant and roots at all zinc concentrations tested with no significant difference among treatments except for root length. The roots of A. sessilis at 0 ppm treatment showed significantly higher zinc accumulation (1.43 ± 0.01 ppm) and significantly lower zinc accumulation in stems of 0 ppm treatment (0.20 ± 0.00 ppm). The higher total zinc uptake by the A. sessilis at 0 ppm (control) treatment (2.04 ± 0.03 ppm) and the lower observed at 300 ppm treatment (1.26 ± 0.00 ppm). The total zinc accumulation in A. sessilis from various concentrations of zinc treatment were in the order of 0 ppm < 50 ppm < 100 ppm and 200 ppm < 300 ppm zinc concentrations. A. sessilis has the potential to hyperaccumulate zinc which may help to reduce zinc in the soil and clean up zinc in polluted environment.