STRUCTURAL AND CYTOCHEMICAL ANALYSIS OF THE STIGMA AND STYLE IN TIBOUCHINA-SEMIDECANDRA COGN (MELASTOMATACEAE)

Structural and cytochemical aspects of the pistil of Tibouchina semide candra a Cogn. were studied. The stigma is of the wet-papillate type a nd is structurally divisible into a papillar zone and a stigmatic zone . The papillar zone consists of loosely arranged papillae which are ma tchstick-shaped, unicellular, and produce lipid droplets that remain e ntrapped below the thick cuticle. The bulk of cell volume is made up o f large vacuoles rich in tannin. The stigmatic zone consists of layers of secretory cells with dense cytoplasm, actively secreting dictyosom es and numerous rough endoplasmic reticulum (RER) profiles. Free-flowi ng lipid exudate, produced by these cells, is initially stored in the intercellular spaces, and subsequently extruded out to cover the surfa ce. The style is solid with a core of transmitting tissue traversing i ts whole length. The transmitting tissue consists of loosely arranged cells with numerous organelles and conspicuous intercellular substance rich in polysaccharides and pectins. Ultracstructural details indicat e that the intercellular secretion is accompanied with fraying of the wall component. Both the transverse and longitudinal walls contain pla smodesmata. (C) 1995 Annals of Botany Company