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Absorbing Trichomes in the Pleurothallidinae (Orchidaceae)

Alec M. Pridgeon
American Journal of Botany
Vol. 68, No. 1 (Jan., 1981), pp. 64-71
Stable URL: http://www.jstor.org/stable/2442992
Page Count: 8
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Absorbing Trichomes in the Pleurothallidinae (Orchidaceae)
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Abstract

Glandular trichomes occur on both surfaces of leaves of all examined genera and species of the subtribe Pleurothallidinae (Orchidaceae). Trichome initiation is effected by one periclinal division of a protodermal cell, producing a thin-walled, globose apical cell with a relatively large nucleus and a subapical stalk cell with heavily cutinized lateral walls. In some species a second periclinal division produces a third small basal cell also having thick lateral walls but thin transverse walls As leaf development proceeds, the trichome apparatus assumes a sunken position due to continued anticlinal divisions of protoderm Prior to laminar expansion and guard-mother-cell division on the abaxial surface, the wall of the apical cell ruptures and is replaced by a brown opaque residue Finally, after vascular tissue differentiation and the cessation of meristematic activity, two or more pitted foot cells develop at the base of the trichome and adjacent to the water-storing hypodermal layers. Preliminary investigations indicate that the trichome apparatus is absorptive throughout its development and similar in function to tillandsioid scales in Bromeliaceae

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