epiphyte(redirected from air plants)
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a plant that grows on other plants, mainly on the branches and trunks of trees. (Epiphytes that grow on the leaves of other plants are called epiphylls.) Epiphytes, unlike parasites, obtain their nutritive substances from the environment and not from the host plant.
Epiphytes exist in all classes of plants. They occur in the greatest numbers in moist, warm regions, especially in tropical forests, where both lower and higher epiphytes are found (mainly from the families Orchidaceae and Bromeliaceae). There is an abundance of epiphytes in moist, less warm regions, including mountainous areas, where they are represented primarily by mosses, lichens, and ferns. The predominant epiphytes in damp cold regions are mosses, lichens, and aquatics. Semi-epiphytes (many Araceae, banyan, and others) begin their development on trees and then form long hanging adventitious roots that penetrate the ground for water and mineral substances.
During the evolutionary process, true epiphytes have developed adaptations for catching water and mineral substances from the air. These adaptations include spongy covers on the roots and root pockets—that is, roots woven together to form baskets in which dust and fallen leaves accumulate. Soil is thus produced for the feeding roots (for example, Asplenium and Grammatophyllum). Some epiphytes have recessed leaves that form a niche on the stalk in which soil is accumulated (for example, Platycerium). In some Bromeliaceae the leaves form a cone in which water accumulates; the water is then sucked up by hairs on the inner surfaces of the leaves.
Many epiphytes have developed adaptations to economize on water consumption. The adaptations, similar to those in xerophytes, include the development of dense leaves with a thick cuticle, a reduction in leaves, the formation of special compartments for water storage, and the appearance of a pubescence on the leaves.
Epiphytes developed during the evolutionary process apparently in connection with the special ecological conditions in shady, damp places, moving from the dark lower tiers of forests toward the light on the branches of trees. Early epiphytes probably had small, lightweight seeds and spores that could be disseminated even by the slightest air currents.
REFERENCESPoplavskaia, G. I. Ekologiia raslenii, 2nd ed. Moscow, 1948.
Alekhin, V. V. Geografiia rastenii, 3rded. Moscow, 1950.
Schmidthüsen, J. Obshchaia geografiia rastitel’nosti. Moscow, 1966. (Translated from German.)
Walter, H. Rastitel’nost’ zemnogo shara, vol. 1. Moscow, 1968. (Translated from German.)
N. I. SHORINA