Tamil Nadu

The ornamental plant that grew to ravage Tamil Nadu’s water bodies

Seeing red over green: Neyveli kaatamanakku and the 'aligator weed' that is being sold as ponnanganni.  

It has done to water bodies what seemai karuvelam (Prosopis juliflora) did to Tamil Nadu’s lands. Ipomea carnea, also known as Neyveli kattamanakku has clogged every water body in the State and proved detrimental to its aquatic ecosystems.

“Ipomea carnea is a seemai karuvelam without thorns. Other species, including Alternanthera philoxeroides (seemai ponnanganni), those belonging to the genus Sphagneticola (such as seemai karisalanganni) and Eichhornia crassipes (ahaya thamarai) have invaded the aquatic ecosystem of Tamil Nadu, including wetlands,” said D. Narasimhan, professor and head of the department-plant biology and plant biotechnology at Madras Christian College who, along with his colleagues W. Arisdason, Sheeba J. Irwin and G. Gnanasekaran, has conducted a study on invasive alien plant species in Tamil Nadu.

Such species were either introduced as ornamental plants or entered India inadvertently. The changes in the habitat or ecosystem turn the alien species invasive. Ipomea carnea was introduced as an ornamental plant. Similarly, Eichhornia crassipes (ahaya thamarai), which has now occupied water bodies in a big way, was introduced by Lady Wellington during her stay in Calcutta.

“Ipomea carnea is a highly adaptive plant, which thrives both in inundated as well as dry conditions. It has the capacity to turn a river into soil, invite other plants and in the process create islands in water bodies. It affects the flow of water,” says K.V. Krishnamurthy, former head of the department of plant science at Bharathidasan University, who has studied island formations by the plant in the river Cauvery.

Gaining acceptance

Dr. Narasimhan said the invasive plants also turn the water bodies shallow and gradually gain acceptance in human settlements. “Ipomea carnea leaves have replaced aaduthinnapalai for making garlands and erecting fences,” points out Mr. Narasimhan.

The invasive species also pose health hazards, particularly seemai ponnanganni and seemai karisalanganni, which are actually sold as native plants in markets. “Seemai ponnanganni grows even in sewage and industrial waste, absorbing lead, mercury and ammonia. The metals enter the body of those who consume the plant. Moreover, seemai karisalanganni does not possess the medicinal values of native species,” says Mr. Narasimhan.

While eradication continues to pose a challenge, Mr. Krishnamurthy said finding positive ways to exploit the plants was the ideal option. “One of my students did his research on hydrocarbons with Ipomea carnea. The plant has latex that can be used with some value addition. The pure cellulose in Eichhornia crassipes has the potential to be a source for paper-making. In Kolkata, there is such a technology for making handmade paper,” said Mr. Krishnamurthy. Eichhornia, Mr. Narasimhan said, was already used as a natural manure in many parts of the State.


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Printable version | Jun 18, 2021 2:15:21 PM | https://www.thehindu.com/news/national/tamil-nadu/the-ornamental-plant-that-grew-to-ravage-tamil-nadus-water-bodies/article17744805.ece

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