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Brocchinia acuminata - Amuri Tepui, Venezuela

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The Tepuis of the Guyana Shield in the border region of Venezuela, Guyana and Brazil are famous for being one of the worlds most remote and fascinating landscapes. These sandstone plateaus are very poor in nutrients and thus the well known home of various carnivorous plants. But various Ant Plants are found there as well.



One of them, Brocchinia acuminata is a Bromeliad that occurs on several Tepuis. Ants live in the bulbous "onion-shaped" structure that is formed by the leaf-bases:



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Brocchinia acuminata Lyman Bradford Smith published in Brittonia 3, 1939.

  This terrestrial species is often larger than ‘bulbous’ Tillandsia species but it does have a somewhat analogous form with enclosed hollows in which ant colonies choose to reside.  Indeed, fifty percent of plants examined in habitat were ant occupied.  (Givnish et al.1997.)

  However, here leaves are not as tightly closed above interior hollows as they are in Tillandsia, thereby allowing some water inside. This is perhaps because nutrient absorption inside the tanks of Brocchinia species occurs mostly through large, living, shield cells situated at leaf bases.  These cells can die if they become too dry - an important detail for cultivators. In Tillandsia, gas intake is performed through outer layers of dead cells that incorporate vapour gaps, which help to preclude the desiccation of the underlying living cells. (Givnish et al. 1997.)

  Hints that these are ant mutualists are provided by numerous adventitious roots that infiltrate the clustered leaf bases and the plant's trichomes are able to absorb the amino acids of decomposition.  Givnish et al., (1997) also postulate that the species may be able to utilize internal supplies of concentrated carbon dioxide (CO²) from ant respiration and that of various detrivore life forms as seen in Dischidia major.  Indeed, B. acuminata stomata are formed in sufficiently large clusters on internal leaf bases to be evident to the naked eye and although their function is not known, they do connect to aerenchyma channels (air-filled connective tissues) that are especially large in this species.  The plant’s photosynthesizing leaf tissues sit some 30 cm (12”) higher than where resident ant colonies are exhaling carbon dioxide so perhaps the aerenchyma tubing transports this gas to where it is needed in photosynthesis. (Givnish et al. 1997.)

Habitats:  This, the most widespread of all Brocchinia species; occurs in tepui scrubs, edges of bogs, and cloud forests both on the top and lower surrounds of eastern and western tepui, hence at diverse altitudes between 600-2100 m (1969-6890 ft.). (Givnish et al. 1997.)

Range:  Colombia and Venezuela. Type record, Venezuela, Edo Bolivar on Auyan tepui, at an altitude of 1850 m. (6070 ft.)

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