Advised naturalists may have already noticed that some flowers are characterized by heat bursts. But one needs to be more than an amateur botanist to circumscribe this phenomenon: it is mostly found in basal species of flowering plants: in Arum (Araceae) of course, less known but still described in Magnolia, and also, which surprised me as I was reading this paper (1), in water lilies (Nympheaceae) and lotus (Nelumbonaceae). Flower thermogenesis is a feature of coleoptera pollination syndrome, when beetles are the main pollinators.
The study describes the phenomenon in this terrible species you must already know, even if you never had any botany class:
Victoria amazonica. It is this huge leafy water lily as illustrated here, and it grows in the Amazonian basin, but does as well in tropical greenhouses basins from a botanical garden.
A priori, the reason for these metabolical bursts, temporarily heating the flowers in thermogenic species, is that it allows flowers to diffuse their scent more efficiently in the cold of dawn. This huge water lily nevertheless shows the other oddity that its flowers just have a nocturnal temperature being constantly above the outside temperature, 5 more celsius degrees in average, while all other species in which thermogenesis is known only have heat burst at the beginning of the night, the time to attract pollinators.
It seems that this feature may be another reward to these famous pollinators: warmer temperature in the floral lodge allows the beetles to keep an intensive ongoning activity, either for a honey-moon or for a free-lunchat the expense of the host. Indeed, these pollinators are coleoptera (from the Genus Cyclocephala, and this one may well be the main pollinator of V. amazonica and is called C. hardyi), and the price is heavy for beetles are generally so voracious and eat much of pollen before they would even act as pollinators.
But this warm gift doesn’t last forever. Flowers of this species only live two days: a first night as a female waiting for guests loaded with pollen from their previous party, a second one in the male phase to disperse their own.
(1) Seymour, R S, and Matthews P G D, 2006. The Role of Thermogenesis in the Pollination Biology of the Amazon Water lily Victoria amazonica. Annals of Botany 98: 1129-1135.
Photographs are courtesy of:
Leaves http://www.flickr.com/people/ligia/
Flower http://www.flickr.com/people/mauricem/
Pollinator http://www.flickr.com/people/junglenews/
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