Notes on the structure of the stigma of Polygala virgata var. virgata (Polygalaceae)

Structural and cytochemical aspects of the stigma of Polygala virgata Thunb. var. virgata were studied. Flowers of an isolated group of plants were used. Indications are that the plants are autogamous. The stigma is of the wet papillate type with unicellular papillae forming the receptive surface of the stigma. Exudate production commenced at an early stage, more than six days before onset of anthesis and appeared alveolar or fibrillar. The papillar cell wall material became loosely arranged and the cytoplasm senescent. All stigmatic exudate is secreted by the papillar cells and is contained in the subcuticular space. The cuticle showed no signs of disruption, but exudate appeared on the papillar surface during middle anthesis. Cytochemical tests indicated the presence of lipids, pectins and some proteins in the exudate, while no polysaccharides were indicated. No protein pellicle was observed. The papillar cytoplasm showed signs of disruption during the middle anthesis stage of development and contained lobed plastids, endoplasmic reticulum plates and small vacuoles.