Adattamenti fisiologici alla vita « aerea » nel genere Tillandsia

Abstract

Physiological adaptations to « aerial » life in the genus Tillandsia.—Ten « atmospheric » Tillandsia species, with different degree of adaptation to drought, were investigated to verify the occurrence of CAM and to determine their daily transpiration pattern.

Most of the species were collected during the Botanical Expeditions of the Accademia dei Lincei in Latin America in 1969 and 1971. All species had been maintained in the greenhouse of the Naples Botanical Garden during the winter months and in the open air during the warmer months, previous to experiments. The diurnal cycle of transpiration, the malic acid content and cell sap pH of the leaves were studied under outdoor conditions. Curves of malic acid and pH variations typical of CAM have been obtained for all the examined species. Moreover, the transpiration data indicate that stomata are open at night. The rates of transpiration appear to be extremely low. The highest transpiration rates refer to the species of the relatively moister habitats, the lowest to the more xeric species. Results indicate that CAM and low rates of transpiration are ecological adaptations to extremely dry habitats.