Heliamphora nutans Benth. (Sarraceniaceae)

.



Lithograph of Heliamphora nutans from 'Curtis's Botanical Magazine' (1890, t. 7093). Specimen of Heliamphora nutans collected by the Schomburgk's from Mount Roraima in 1842-43 (Oxford University Herbaria).


Growing in the marshy highlands of the Guiana Shield, the pitcher plant Heliamphora nutans is intricately adapted to its environment. Produced by a 1.7 billion year old Precambrian sandstone formation in northeast South America, the Guiana Shield underlies Guyana, Suriname, French Guiana and parts of Brazil, Colombia and Venezuela.

In 1978, Ken Burras (Superintendent of the Botanic Garden between 1963 and 1988) joined a Kew Expedition to Mount Roraima, Guyana; where Heliamphora was originally collected by botanist Robert Schomburgk in 1839. The Expedition returned with 400 plant collections, including Heliamphora. The Oxford Botanic Garden soon developed expertise in growing these challenging plants, but they were highly collectable, being rare in cultivation. Consequently, it was difficult to stop visitors from stealing them.

In 1987, Ken passed some of the plants to the Micropropagation Laboratory of the Oxford Forestry Institute, formerly part of the Department of Plant Sciences. Led by Stephen Woodward, the team developed an efficient propagation process and was soon able to introduce the plant widely into cultivation. More importantly, sufficient specimens were grown to enable the plant's continuous public display at the Garden. Some of the plants growing at the Botanic Garden today are direct descendants of the original Mount Roraima collection.

In 1989, Oxford-based botanist Barrie Juniper and colleagues proposed four traits to define the true carnivorous syndrome. Plants (i) attract prey using special signals; (ii) trap and kill prey using specially evolved structures; (iii) digest prey by secreting enzymes; and (iv) have specialised structures to absorb nutrients from the digested prey, whilst the presence of commensals indicates a long evolutionary history of the carnivorous trait. Under this definition, Heliamphora nutans becomes a 'doubtful carnivore' since the presence of digestive enzymes in its pitchers has never been confirmed.

The pitchers are supremely adapted to catching insects. They have a red, sticky nectary zone right at the top containing two types of nectar glands. On the internal surface of the top-half of the pitcher is a zone of downward pointing hairs, surrounding a smooth attractive area. The pitcher constricts and then widens with the lower half covered in hairs, which become denser towards the bottom. It has recently been shown that when wetted these hairs become extremely slippery and that insects "aquaplane" into the pitcher, thereby increasing the trapping efficiency. Each pitcher also has an overflow mechanism; a drainage hole at the constriction between the top and bottom halves.

Further reading

Bauer U et al. 2013. 'Insect aquaplaning' on a superhydrophilic hairy surface: how Heliamphora nutans Benth. pitcher plants capture prey. Proceedings of the Royal Society Series B 280, 20122569.

Joel DM et al. 1985. Ultraviolet patterns in traps of carnivorous plants. New Phytologist 101, 585-593.

Juniper BJ et al. 1989. Carnivorous plants. Academic Press.

Alison Foster