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Melastoma malabathricum and buzz pollination

on 7th December 2014

Singapore Rhododendron or Sendudok (Melastome malabathricum) is commonly seen throughout the tropics. The plant is fast growing, producing attractive, pinkish mauve flowers with two types of stamens. There are five short stamens with yellow filaments (stalks) and anthers (pollen sacs) and five long stamens. The long stamens consist of two parts – the basal part is straight and yellow and the upper part curved and mauve. There are two short horns at the junction where the two parts join. The anthers are found at the ends of the curved filaments. Arising from the centre of the flower is the long pinkish style that ends in a green stigma – see image above.

Note that all ten stamens have pores at the tips of their anthers (above, long stamens; below, short stamens). These pores are where the pollen grains shoot out, triggered by the high frequency vibrations of the bee’s wings, onto the bee’s body. This can be demonstrated with a tuning fork of the right pitch when placed next to the stamens.

The large Carpenter Bees as well as smaller bees (this needs confirmation) collect pollen this way, known as buzz pollination LINK.

Unlike anthers of Melastoma malabathricum, those of most other plants rupture along defined lines to expose the pollen grains for bees, ants and other pollinators to collect (see above and below). The images above, left showing the stamens of MacArthur Palm (Ptychospermum macarthuri) and right those of Sweet Basil (Ocimun basilicum), the pollen are the many blobs of white found on the pollen sacs.

The Halictid Bee or Sweat Bee (Anthophora zonata, Family: Halictidae), whose body is black with broad bluish-green metallic banding (above), can be seen gripping the tips of the long as well as the short stamens to get at the pollen (see video below). At times, these bees grab at the stigma of the style, mistaking it for the tip of the stamen. By doing this, the bees transfer pollen, either taken from the same flower or from different flowers and in the process indulge in self or cross pollination respectively.

YC Wee
Singapore
November 2014

If you like this post please tap on the Like button at the left bottom of page. Any views and opinions expressed in this article are solely those of the authors/contributors, and are not endorsed by the Lee Kong Chian Natural History Museum (LKCNHM, NUS) or its affiliated institutions. Readers are encouraged to use their discretion before making any decisions or judgements based on the information presented.

YC Wee

Dr Wee played a significant role as a green advocate in Singapore through his extensive involvement in various organizations and committees: as Secretary and Chairman for the Malayan Nature Society (Singapore Branch), and with the Nature Society (Singapore) as founding President (1978-1995). He has also served in the Nature Reserve Board (1987-1989), Nature Reserves Committee (1990-1996), National Council on the Environment/Singapore Environment Council (1992-1996), Work-Group on Nature Conservation (1992) and Inter-Varsity Council on the Environment (1995-1997). He is Patron of the Singapore Gardening Society and was appointed Honorary Museum Associate of the Lee Kong Chian Natural History Museum (LKCNHM) in 2012. In 2005, Dr Wee started the Bird Ecology Study Group. With more than 6,000 entries, the website has become a valuable resource consulted by students, birdwatchers and researchers locally and internationally. The views and opinions expressed in this article are his own, and do not represent those of LKCNHM, the National University of Singapore or its affiliated institutions.

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