Wednesday, August 29, 2012

Do That Thing Like That Sundew Do

Round Leaved Sundew, Drosera rotundifolia
Wetlands present a number of challenges and advantages to their constituent plant communities. Fens and bogs especially have very low nutrient availability due to a combination of water logged soils and high or low pH, but they are areas of high light levels, meaning there is little obstruction to photosynthesis. As such, their associated suites of plants often exhibit a high degree of adaptation to cope and thrive in these conditions. The most striking of these is undoubtedly those plants that have evolved carnivory to deal with the their nutrient-poor environments. Sundew plants are often the most striking of these as, despite their often small size, their fly-paper like leaves turn a wonderful crimson colour as they age. Ireland is home to three species of Sundew, of which the Round Leaved Sundew (Drosera rotundifolia) is the most common (1). The upper surface of the highly specialised leaves, which are arranged in a basal rosette, are covered with tentacles, each of which has a drop of mucus, the sundew, that is composed of complex polysaccharides (2). Insects attracted by the vibrant colours of the leaves an the sundew itself become stuck to the mucus. The tentacles, then wrap themselves around the insect making escape impossible. Proteolytic enzymes secreted by the plant then digest the insect, with any resulting carcass being expelled from the leaf.
Leaf of Round Leaved Sundew, Drosera rotundifolia
D. rotundifolia, along with other Drosera species, has long been used in folk medicine as a treatment for a variety of respiratory problems. Such is the efficacy of the plants that many species are faced with extinction in the wild from over collection (3). Much of D. rotundifolia physiological activity comes from the presence of a number of 1,4-naphthoquinones (4). Many of these have been shown to be inhibitors of seed germination in many plants and to have inhibitory and toxic activity against certain insects and fungi. Investigations into the activity of D. rotundifolia extracts on human cells has shown that it suppresses inflammatory response in mast cells (3). These cells play an important role in allergic and inflammatory reactions. Mast cell-mediated allergic inflammation is involved in many diseases, including asthma by releasing proinflammatory compounds such as cytokines and histamine and any suppression of these responses would be of great benefit to sufferers of that disease.

Round Leaved Sundew, Drosera rotundifolia
  1. Sterry, 2004. Collins Coplete Guide to Irish Wildlife p. 206
  2. Thorén et al., 2003. New Phytologist 159 pp. 507-511
  3. Fukushima et al., 2009. Journal of Ethnopharmacology 125 pp. 90-0696
  4. Hirsikorpi et al., 2002. Plant Science 162 pp 537-542

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