MSc

A study on 'Biodiversity of medicinal plants in Vellayani' was carried out in
and around Vellayani lake of Thiruvananthapuram district, Kerala. The objectives of the
study were to identify the medicinal plants from among the existing natural flora, to study
the growth behaviour of selected medicinal plants and to assess the pharmacologically
active constituents of selected medicinal plants.
A total of 80 sampling units were taken usmg stratified random sampling
technique, the strata being dry land, garden land, paddy field and lake area. The
medicinal plants in dry land, garden land and paddy field were identified and quantified
by random sampling technique using 1.0 m2 frame. In the lake area as it was difficult to
use the frame the plants were collected randomly giving sufficient representation. A total
of 135 plant species were identified in the four different strata belonging to 120 genera
and 57 families. None of the plants were endemic. There were 118 indigenous and 17
exotic or naturalized plants. Ten important medicinal plant species were selected for
detailed study and their' growth behaviour was monitored for one year. They were
Andrographis panieulata, Cyclea peltata, Desmodium velutinum, Eclipta alba, Gloriosa
superba, Hemidesmus indieus, Phyllanthus amarus, Scoparia duleis, Sida rhombi/alia
and Solanum indieum.


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Emilia sonchifolia dominated in dry land area with high relative density and
relative frequency. Centella asiatica was the dominating species in garden land and
paddy field with high relative density. Limnophila repens was the dominant species in
lake area.
Most frequently occurring species in dry land was Emilia sonchifolia and in
garden land Scoparia dulcis and Vernonia cinerea. Centella asiatica and Eclipta alba
occurred more frequently in paddy field, where as in lake area Hydrilla verticellata
occurred more frequently.
The rare species in dry land were Abrus precatorius, Blepharis medaraspatensis,
Carissa congesta and Rauvolfia serpentina. In garden land Acalypha indica, Capparis
brevispina, Cayratia pedata, Catharanthus roseus var. alba were found to be rare. In
paddy field Borraria alata, Coldenia procumbens and Portulaca oleraceae were found to
be the rare species. Diplocyclos palmatus was the rare species in lake area.
Dry land and garden land were found to be the most similar strata with more
number of species in common. Dry land and lake area were found to be the most
dissimilar strata in vegetation pair wise analysis.
Lake area was found to have higher concentration of dominance as expressed by
Simpson's index. Shannon's index was maximum in dry land area. Abundant species
occurs more in dry land area. In dry land almost all species had equal number of
individuals since Evenness index was maximum.

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Growth characters like plant height, plant spread, height of the first branch,
number of leaves, number of roots, root length were found to increase from pre-flowering
to seed set stage. These characters were found to be high in garden land compared to
other strata in most of the species. The fresh and dry weight of officinal part was more in
garden land condition in most of the species.
In the chemical analysis it was found that in Limnophila repens there was no
similar chemical constituents as that of Bacopa monnieri (brahmi). There was no
bacoside content in Limnophila repens, which is present in Bacopa monnieri. So
Limnophila repens cannot be used as a substitute for brahrni.
The andrographolide content in Andrographis paniculata was found to be
slightly higher in dry land compared to garden land. The andrographolide content was
higher in dry land area because of the water stress condition in dry land.
The results of this study will be helpful in evolving suitable strategies for
sustainable utilization of medicinal and aromatic plants, occumng as indigenous and
naturalized in and around the Vellayani lake. Such an effort would also help to conserve
many of the weed species which have very high medicinal values.