14 December, 2018

Movements of floral parts in Bulbophyllum

by Tan, Keng Hong and Tan, Lin Tze

Bulbophyllum is the largest genus of the orchid family, with about 2000 species that are mainly pollinated by flies. Many of these species are known for releasing odours that humans find unpleasant. There are, however, many Bulbophyllum species whose flowers specifically attract true fruit fly pollinators – especially certain fruit fly pest species – with spicy or pleasant floral odours.

Non–nectar-producing and non-resupinate (untwisted floral stalk) solitary flowers of Bulbophyllum pratervisum emit pleasant floral fragrances to specifically attract and reward male fruit flies. They have slippery surfaces on their lateral sepals that specifically aid in pollination. Although pollinia (packages containing fine pollen grains) removal by male fruit flies has been observed frequently, the depositing of pollinia to complete pollination (by two males belonging to different fruit fly pest species) has only been observed recently.
Field observations show two previously unreported movements of floral parts – a) petals and medial sepal during daily closing of flowers (for the night, to deter unwelcome visitors) and reopening (to welcome fruit fly visitors/pollinators), and b) the spring-loaded, hinged lip (a highly modified petal) during removal and deposition of pollinia by a male fruit fly.
Additionally, a third (novel) movement has been observed, either when the flower closes for the night to protect the stigma, or after a fly has deposited the pollinia onto the stigma – the 'acute tooth' on each column wall folds inwards to secure the newly deposited pollinia, like a mother hugging an infant close to her chest.  

Read the scientific publication in JPE.

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