Polysaccharide Secretion by the Watermelon Stigma

Publisher Website
Google Scholar
Abstract
Secretion of the galactose-containing polysaccharide component of the watermelon stigma exudate was studied using electron microscopy cytochemistry and autoradiography. Polysaccharide localization using the thiosemicarbazide–silver proteinate method stained the Golgi apparatus and secretory vesicles, the cell wall, wall thickenings and extracellular secretion. The same result was obtained at anthesis and at 18 h prior to anthesis, which coincides with the period of maximum secretion. Labelling of stigmas in vivo with D-(1-3H) galactose at 20 h prior to anthesis resulted in different labelling patterns after 2 h (18 h prior to anthesis) and 20 h (anthesis). At 18 h prior to anthesis label was present in the Golgi apparatus and secretory vesicles, the cell wall and wall thickenings. By anthesis label had accumulated in the extracellular secretion in addition to the Golgi apparatus, secretory vesicles, cell wall and wall thickenings. The results suggest that the polysaccharide component of the stigma exudate is produced in the Golgi apparatus and secreted via the cell wall and wall thickenings.