What is it about?
The growth response, metal tolerance and phytoaccumulation properties of water spinach (Ipomoea aquatica) and okra (Abelmoschus esculentus) were assessed under different contaminated spiked metals: control, 50 mg Pb/kg soil, 50 mg Zn/kg soil and 50 mg Cu/kg soil. The availability of Pb, Zn and Cu metals in both soil and plants were detected using flame atomic absorption spectrometry. The concentration and accumulation of heavy metals from soil to roots and shoots (edible parts) were evaluated in terms of translocation factor, accumulation factor and tolerance index. Okra recorded the highest accumulation of Pb (80.20 mg/kg) in its root followed by Zn in roots (35.70 mg/kg) and shoots (34.80 mg/kg) of water spinach, respectively. Different accumulation trends were observed with, Pb > Zn > Cu in okra and Zn > Pb > Cu in water spinach. Significant differences (p < 0.01) of Pb, Zn and Cu accumulation were found in both water spinach and okra cultivated among tested treatments. However, only the accumulation of Pb metal in the shoots of water spinach and okra exceeded the maximum permissible levels of the national Malaysian Food Act 1983 and Food Regulations 1985 (2006) as well as the international Codex Alimentarius Commission limits. This study has shown that both water spinach and okra have good potential as Pb and Zn phytoremediators.
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Why is it important?
Water spinach and okra are commonly grown vegetables in Malaysia and many other sub-tropical countries in Asia-Pacific region yet many of the existing agricultural lands are easily exposed to all kinds of soil contaminants including the hazardous heavy metals such as lead (Pb), zinc (Zn) and copper (Cu). Limited past studies have performed to investigate the phytoextraction (accumulation of heavy metals) properties of these vegetables in contaminated soils yet there are currently no robust studies that have examined the comparative and empirical assessment of heavy metals accumulation in water spinach and okra vegetables with the national and international permissible food standards.
Perspectives
In this paper, we reported on the different growth response, metal tolerance and phyto-accumulation properties of both water spinach (I. aquatica) and okra (A. esculentus) vegetables that commonly grown for daily consumption in Malaysia and other sub-tropical countries growing under the contaminated soils. Both vegetables underwent pot assay experiments with the assigned concentration levels of artificially spiked heavy metal contents in the contaminated soils. The translocation and concentration of heavy metals accumulated in both of the vegetables were then evaluated based on the tolerance index, translocation factor and accumulation factor. Overall, the results showed that both water spinach and okra have relatively good tolerance responses to survive under extreme contaminated levels of various heavy metal contents in the clay soil. We also discovered that both water spinach and okra are Pb and Zn phyto-remediators; of which both vegetables are not advisable to cultivate under extreme Pb contaminated soil due to biomagnification effects for human health (exceeded the allowable national and international standards).
Assistant Professor Dr Chuck Chuan Ng
Xiamen University Malaysia
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This page is a summary of: Heavy metals phyto-assessment in commonly grown vegetables: water spinach (I. aquatica) and okra (A. esculentus), SpringerPlus, April 2016, Springer Science + Business Media,
DOI: 10.1186/s40064-016-2125-5.
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