Invasive plant species such as alligator weed, which threatens natural ecosystem, could be promoted as a food product to sustainably manage excessive growth of these alien invaders as well as strengthen food security, suggests a new study.
Researchers at the Indian Statistical Institute and University of Kalyani checked the toxic heavy metal concentration (particularly lead, cadmium and chromium) in the water, sediments and plants growing in 11 contaminated aquatic water bodies in the vicinity of industrial units in Kolkata.
‘Water spinach is very popular as a green leafy vegetable in countries like India, Bangladesh, Thailand, China, Vietnam and Philippines.’
They mapped and contrasted the toxic metal uptake and accumulation in native and invasive plant species in those sites. These metals are a cause of environmental pollution from sources such as leaded petrol, industrial effluents and leaching of metal ions from the soil into lakes and rivers by acid rain.
In excess, they can damage human health. They accumulate and disrupt function in vital organs and glands such as the heart, brain, kidneys, bone and liver. Alligator weed and water hyacinth were the invasive species investigated in the study while water spinach and others were the native plants examined.
"All plant species were able to accumulate heavy metals without showing any toxicity symptoms. Alligator weed and water hyacinth are very common in aquatic sites in India and grow rapidly and spread quickly thereby displacing native species that have economic and medicinal value, in addition to causing bio-diversity loss," Poulami Jha of ISI's Agricultural and Ecological Research Unit told IANS.
Incidentally, alligator weed is consumed by tribal communities although it is not as popular as the naturally occurring water spinach. Both take up heavy metals from the surrounding water and sediment.
The study showed the alligator weed hoarded up a large amount of heavy metal in its roots, whereas in its edible part, translocation of heavy metal was very low compared to that in the edible part of water spinach.
"This could be a good thing for an edible plant. But water spinach poses a serious threat. Therefore, this plant should be eaten with caution," Jha informed. Water spinach is very popular as a green leafy vegetable in countries like India, Bangladesh, Thailand, China, Vietnam and Philippines.
"Its above ground part is edible and in many places it is cultivated with wastewater. So high translocation of heavy metal in its edible part could pose danger to humans as it will be biomagnified (concentration increases several-fold) when travelling through food chain," she explained.
Key takeaways from the study published in November in the American Journal of Plant Sciences indicate management of excessive growth of invasive plants in a developing country like India could be carried out without spending a lot of resources.
Alok C. Samal, Subhash C. Santra and Anjana Dewanji are the co-authors of the study.
"This plant (alligator weed) can be promoted as food since it shows very low translocation of heavy metals in its edible plant. So, without any cultivation the natural growth of this species could be used for repeated harvesting, thereby meeting a portion of the food requirement and managing the excessive growth of this species. This could pave the way for a sustainable future with this invasive species," Jha said.