Ultrastructure of Glandular Ovarian Trichomes of Cypripedium Calceolus and C. Reginae (Orchidaceae)

Trichomes on the orchid ovary are a possible site of synthesis and secretion of the floral scent. Scanning electron microscopy of these trichomes shows a bulbous cell on a two‐celled stalk. Thin sections of the tip cell revealed the morphology of an active, secretory cell with unusual coated vesicles in the extra‐cellular deposition. Abundant smooth endoplasmic reticulum (ER) aggregated beneath the plasma membrane in the apical region of the cell and the limited dictyosomes in the cell suggest direct secretion by ER. Numerous lipid droplets are present in the apical area. Plastids, found only in the basal region of this cell, are more round in profile than typical chloroplasts and contain only a few unstacked thylakoids and a limited membranous reticulum. In addition to the normal plastid envelope, a double layer of membrane (probably ER) is tightly appressed to each dense, starch‐free plastid. Highly specialized morphology and subcellular localization of organelles suggest the secretory nature of these trichomes.