Developmental and Structural Section
Hayden, W. John , Drake, M. J. .
Structure and Development of Foliar Glands of Stizophyllum riparium (Bignoniaceae).
We studied structure and development of epidermal glands associated with pellucid punctae found throughout the shoot system of Stizophyllum. Specimens of Stizophyllum riparium were collected from Kaxil Kiuic, the Helen Moyers Biocultural Reserve, located in the state of Yucatan, Mexico. Leaves and stem tips were prepared for study with light and scanning electron microscopy using standard techniques. Glands occur on both leaf surfaces but are more frequent on the abaxial side. Each gland is roughly saucer-shaped and consists of a cluster of three or four basal/stalk cells attached to the epidermis and a more or less flat disk of elongate cells that radiate from the base/stalk and terminate at the upturned margin. Glands are approximately 0.1 mm in diameter. Secretion appears to be merocrine-eccrine but the nature of the secretory product remains unknown. Glands develop from protoderm and their maturation is precocious relative to adjacent tissues. Mesophyll near the center of each gland remains undifferentiated whereas typical palisade and spongy layers differentiate throughout the rest of the lamina. Initially, glands project above the plant surface, but on adaxial sides of leaves they come to occupy recessed indentations of the surface formed as a consequence of arrested development of superjacent mesophyll. Glands are hyaline in appearance but the pellucid-punctate character of the leaves also depends on the thinness and translucent nature of mesophyll cells located in vertical alignment with the gland base/stalk. A wide range of superficial/epidermal glandular structures have been described from Bignoniaceae, some of the largest and most complex of which include crateriform and patelliform patterns. The relatively simple discoidal epidermal glands of Stizophyllum (tribe Bignonieae) most closely resemble glands described for Incarvillea (tribe Tecomeae). The known range of epidermal gland form in Bignoniaceae can be interpreted as a morphocline including, and perhaps derived from, glandular trichomes.
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1 - University of Richmond, Department of Biology, 28 Westhampton Way, Richmond, Virginia, 23173, USA
2 - University of Richmond, Department of Biology, 28 Westhampton Way, Richmond, VA, 23137, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 551A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 10:15 AM