Pollen-Wall Proteins: Localization, Enzymic and Antigenic Activity During Development in Gladiolus (Iridaceae)

Abstract

Cytochemical methods have been used to follow the incorporation of enzymes and antigens in the cellulosic intine of the pollen grain of Gladiolus gandavensis. Acid phosphatase, esterase and ribonuclease were first detected in the developing intine during the vacuolate period, and by the end of this phase activity was present throughout the intine, especially in the area of the colpus, where this wall layer is thickened. Enzyme activity was also noted in the peripheral region of the protoplast during the period of intine growth. Succinic and NADH (reduced nicotine adeninedinucleotide) dehydrogenase activity was detected in the outer zone of the protoplast, and, at the end of pollen development, in the interbacular cavities of the exine and the pollen-coat meterials, but at no time were these enzymes found in the intine. The appearance of the antigens was traced during pollen development. Antigens were first detected in the early vacuolate period, soon after the release of the spores from the meiotic tetrads. They were found to be associated with the intine from the first deposition of polysaccharides in this layer. As the intine thickened, so the amounts of associated antigens were found to increase, especially in the neighbourhood of the colpus. In slurries prepared using mature pollen, enzymes and antigens were found to diffuse into the medium even with preparation times as short as 30 S. The leakage was over the whole of the exine, not only in the vicinity of the colpus; this may be related to the thinness of the exine in Gladiolus and the presence of pores in the tectum. Electron micrographs showed the presence of vesiculate and tubular cavities in the intine, containing fibrillar or granular material. These inclusions are presumed to be the sites of the enzymes and antigens, since in a related genus, Crocus, acid phosphatase has been shown to be present in the corresponding cavities. Gel diffusion and immunoelectrophoresis showed the presence of 4 major antigenic fractions in the leachates from mature Gladiolus pollen. Tests with the antiserum against leachates from species of the related genus, Iris, showed 1 cross-reacting fraction.