Материал из Антэкология /// Anthecology
Pollen Wall Development in Gibasis (Commelinaceae)
The development of the one and-inline of the pollen wall are described for Gibasis karwinsk yana and G. venustula. During the tetrad stage the appearance of electron-opaque depositions or tri-partite plates at discrete sites between the plasma membrane of the spore and the inward surface of the callose special wall are the first indications of exine development. The sulcus rapidly differentiates being composed of discrete exine granules on a thin foot layer. Probacula in non-apertural areas develop in an electron-opaque granular layer situated between the plasma membrane, which is highly convoluted, and the callose special wall. A foot layer is formed from electron-opaque lamellae at the plasma membrane. Exine pattern is clearly established within the tetrad.After release of the spores from the tetrad an intimate association is rapidly developed between the plasma membrane of the periplasmodial tapetum and the newly-formed exine. Compacted electron-opaque material is found at the interface between membrane and the exine and vesicular material is added from the tapetum. The increase in volume that occurs in both spore and anther is accompanied by considerable vacuolation.Intine development begins just prior to pollen grain mitosis and continues rapidly at the aperture. The thin foot layer becomes discontinuous. Further intine deposition takes place after mitosis and a bilayer is apparent in mature grains. The matrix of this layer contains conspicuous electron-opaque platelets. The exine of the mature spore stains less intensely than in the young spore and the interbacula spaces are filled with material from the degenerate tapetum.