The scent of death

Cuttings #1, October 2011

Orchidologists find themselves doing the oddest things.

Timotheüs van der Niet at the University of KwaZulu-Natal in South Africa was obliged to collect roadkill for his latest research into orchid mimicry, he reports.

The lurid-looking orchid Satyrium pumilum grows in sandy, moist conditions near small streams across the Cape, but it is something of an enigma. They flowers have no nectar – so to attract insects to pollinate their flowers they lure flies into its flowers by mimicking the smell of rotting flesh. Van de Niet wanted to know more and came up with a rather macabre plan. He would compare the scent exuded by the orchids with that of roadkill, in the form of ‘dassies’ or rock hyraxes, that resemble guineau pigs.

Van der Niet explained: ‘We examined the flies visiting the dead dassies, and compared them to the flies visiting the orchids.’ Curiously, they didn't report many flies visiting the flowers, but when they examined a carcass, they spotted clouds of flies carrying orchid pollen. However, they were mostly flesh-flies and mostly females. Subsequent studies showed that flesh-flies were better at finding such a food source.

He concluded that the orchid is quite picky: ‘Not only do they have to entice flies in, but they have to get flies of the right size into the right position to pick up the pollen. Scent plays a hugely important role in pulling in the flies, and even inside the flower different scents attract the flies into the right location to pick up the pollen. The combination of smell and sight is irresistible to some flies. The level of carrion mimicry is amazing; we even saw a female fly leave larvae in a flower because it thought it was carrion.’

Meanwhile, in New Zealand, University of Otago researchers have uncovered two orchid fossils some 20 million years old, which could herald a revolution in understanding of the the Miocene period,

claim paleobotanists.

In the UK, a study is under way to protect rare species such as the fen orchid and early marsh orchid on the coastline of Wales in danger of extinction because sand dunes are stabilising at Kenfig Burrows, in Bridgend county.

Meanwhile, schoolchildren have joined forces with National Trust rangers to help protect rare heathland in Dorset this autumn term by clearing gorse to improve the habitat for bog orchids. In Sussex, an ancient wood is to be revitalised by axing non-native conifers which create too much shade in Brede High Woods, to the detriment of species such as bird’s nest orchid. to ancient woodland.

In Malaysia, orchid-loving Prof Maziah Mahmood has come up with a new technique in plant tissue culture using bioreactors to produce exact copies of a plant. Whereas the traditional method of plant cloning has always been reliant on solid, jelly-like mediums, she has been using a bioreactor to produce up to 10 times that number, using a liquid medium made of natural ingredients such as banana extract and coconut juice.

Finally, if you think repotting a normal sized orchid is a giant nightmare, what if it weighs nearly 136 kilos and hangs over a three-foot deep pool? Brooklyn Botanic Gardens had to tackle a precarious giant tiger orchid (Grammatophyllum speciosum). See how they fared.

Captions

● Satyrium pumilum, Bernd Haynold, wikimedia ● Rock hyrax (Procavia capensis), Cliff, wikimedia ● Bird's-nest Orchid (Neottia nidus-avis),detail of a solitary plant caught (unusually) in a patch of sunlight in otherwise shady woodland, Ian Capper ● Grammatophyllum speciosum, a hand-retouched chromolithograph by Louis-Aristide-Léon Constans (fl. 1830s-1860s), from the second volume of Paxton's Flower Garden (1851-1852) by John Lindley and Joseph Paxton, wikimedia

PK