Tetrad Pollen Grain Development and Sterility in Leschenaultia Formosa (Goodeniaceae)

Summary Pollen of Leschenaultia formosa R. Br. adheres as tetrads linked together on their radial walls by extensions of the bacular strands of sexine sporopollenin after release from the meiotic tetrad. Before release, the tetrads of microspores showed a thickened deposition of primexine polysaccharide on their radial walls, where only slight callose deposits were detectable. The onset of variable sterility in the tetrads was detected as early as the prevacuolate period after spore release. Sterile microspore protoplasts could not he plasmolysed and using the fluorochromatic reaction, showed leakage of fluorescein through the plasma membranes. Sterile grains showed considerable exine development and patterning, which continued until midvacuolate period, but the inner cellulosic intine, layer was absent. In the walls of fertile grains, the enzymic proteins, acid phosphatase and ribonuclease were located in the intine, as found previously with other pollens.