Remarkable discovery by team of scientists:

Sri Lanka abounds with rare flora

By Dhaneshi YATAWARA

Sri Lanka stands unique among the biodiversity hotspots of the world. A remarkably high number of endemic species is found among our fauna and flora with around 23 percent of the flowering plants being endemic. Sri Lanka is home for about 3,360 flowering plant species belonging to 200 plant families. The low country wet zone and mountainous areas in the South West harbour 90 percent of our endemic species.

Rhinacanthus polonnaruwensis

Scientists believe that a significant proportion of our plant genome could remain unknown, even at present. This doubt leads many scientists at all levels to explore the massive floral kingdom of Sri Lanka.

Many discover new properties of plants, be it medicinal or industrial, but a plant totally new to the world would stand out in history.

Such a remarkable discovery was made last year by a team of scientists which included a budding researcher who had graduated in agriculture and a veteran botanist.

A new species of 'Aniththa', a valuable medicinal plant, was discovered by Prabha Amarasinghe and Dr. Siril Wijesundara and was named Rhinacanthus flavovirens . All variants of these plants are known as Aniththa in Sinhala and Nagamulli in Tamil. In English it is known as white crane flower.

According to Amarasinghe, only two species in the genus Rhinacanthus has previously been recorded in Sri Lanka – i.e. Rhinacanthus nasutus named by German botanist Wilhelm Sulpiz Kurz and 'Rhinacanthus polonnaruwensis' by botanist L.H.Cramer described in 1998.

“In Sri Lanka this plant Aniththa is only used for skin ailments. Distinctive features were seen in the different plants, but all were known by one name in indigenous medicine. The Bandaranaike Memorial Ayurvedic Research Institute wanted to find out whether there are different medicinal properties specific to these variations of Aniththa plants – among the already known varieties,” she explained. This was the starting point for her research as her final year thesis in 2008 and examining the two species that existed revealed the existence of a new species.

Rhinacanthus nasutus Kurz and Rhinacanthus polonnaruwensis Cramer are medicinal plant species of Sri Lanka belonging to the plant family Acanthaceae with anti-fungal, anti-bacterial, anti-viral, anti-pyretic and anti-cancer properties. Specimens from seven districts of Sri Lanka were studied for morphological characters. A data matrix with 50 quantitative characters of 111 specimens was derived from the basic data matrix with 88 characters of 122 specimens after eliminating discrete, missing and overlapping data.

The new plant

“I found the new variation and only after I graduated did I start my research to fully describe this new species,” she said. As she discovered, it is the floral patterns that are mostly distinctive in differentiating the three plants.

Rhinocanthus flavovirens

The new species is a perennial herb (a plant that lives for more than two years) which grows up to 20 – 80 centimetres high. Leaves are elliptic – either oval or oblong. Purple marks can be seen in the lower lip of the flower of the R. Nasutus and the corolla tube is straight. R. Nasutus is a woody shrub.

The corolla (petal) of the flower is yellowish green, thus comes the name ‘flavovirens’ which in Latin means yellowish green, according to Amarasinghe. The difference is in the tube that fixes the flower to the branch. In the new variety it is strongly curved. In R. Polonnaruwensis it is almost like a slightly curved 'S'. “The new variety I found in the North Central Province can be found in the dry lowlands of the country,” she said. Unable to find fully grown plants widely available naturally, she examined the specimens available with the Nawinna Ayurvedic Research Institute in Maharagama. “I could confirm that this was a new plant,” she said.

Low availability

During her three-year research, Amarasinghe found that these plants are not abundant. “If we don't take proper steps to conserve these plants, it may seem highly likely that they become a threatened plant species,” she said. Though indigenous medicine uses Aniththa mainly for skin ailments, in many countries research has already begun on its anti-cancer properties, according to Amarasinghe. R. Polonnaruwensis is categorised as endangered.

The next step of the scientists was to compare them with the specimens available at Kew Gardens, England where almost all the plants of the genus 'Rhinacanthus' collected from all over the world were preserved. The scientists had compared specimen plants of the same variety, called Rhinocanthus dichotomous, from coastal Kenya and Tanzania to which the newly discovered plant was morphologically most similar. “The samples those botanists sent closely resembled the Rhinacanthus flavovirens but it clearly showed microscopic differences and the doubts were cleared,” she said.

Variations

Rhinacanthus nasutus

Researchers have found four morphological variations at the initial stage of their research belonging to R. Nasutus, R. flavovirens and two groups for R. polonnaruwensis. The first two are explained above and the two varieties found in the R. polonnaruwensis, corresponding to material collected from the wet and dry zones, showed differences.

The plant from the wet zone had a less hairy stem, shorter leaves and several other differences to that from the dry zone. “These different morphological characters which may simply be ecological adaptations, were not significant enough to place them in separate groups," she said.

According to Amarasinghe the newly discovered plants were thinly distributed in North Central, Central and Southern Provinces in lowland secondary forests.

“This is the first new species I revealed and it is very encouraging to have a veteran botanist such as Dr. Siril Wijesundara support and guide me in this endeavour,” the budding botanist expressed her gratitude. “These days I'm studying for my Master's Degree and I continue to experiment on these plants and microscopically examine their medicinal properties. This is expensive research, but is gaining support.

We may able to see promising results in the future,” she said with bright hopes for a greener future for this valuable research.