Absorptive Trichomes in Brocchinia reducta (Bromeliaceae) and Their Evolutionary and Systematic Significance

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Abstract
Brocchinia reducta, a tank-forming member of subfamily Pitcairnioideae (Bromeliaceae), possesses foliar trichomes capable of absorbing 3H-leucine as do those borne by other members of the same family (all Tillandsioideae and some species of Bromelioideae). In general, pitcairnioid trichomes have been considered incapable of participating in nutrient uptake. Other features of leaf anatomy and physiology, such as the presence of the C3 photosynthetic pathway, suggest that either 1) Brocchinia and tillandsioid tank shoots bearing absorptive hairs are a result of convergence or 2) both subfamilies acquired this feature from the same ancestor. All in all, Tillandsioideae and Pitcairnioideae share more vegetative features in common than either does with Bromelioideae and, thus, may be more closely related than was previously suspected. Tank deployment in Bromelioideae seems to have originated independently from a semi-xeric terrestrial habit that incorporated the CAM syndrome. Factors that could have led to the emergence of absorptive trichomes in Bromeliaceae are identified.