Pollen grain and Ubisch body development in Platanus acerifolia

Abstract

Different stages of development of pollen wall, aperture and Ubisch bodies of Platanus acerifolia (Aiton) Willdenow, have been examined with transmission electron microscopy. Different histochemical techniques for glycoprotein, unsaturated lipids and neutral and acid polysaccharides have been used. At the post-meiotic stage a polysaccharide primexine or glycocalyx is formed around the young microspores. The lipidic, glycoprotein and polysaccharide pro-Ubisch bodies are located between the tapetum plasmalemma and glycocalyx. At the liberation of microspores, glycocalyx increases in conjunction with the pro-columella and the pro-foot layer; elements of the discontinuous proectexine are located in the apertural membrane; pro-sporopollenin-like material is located on the pro-Ubisch bodies. At a more advanced microspore stage, the glycocalyx is fibrillar and the pro-endexine layer is formed under a white line; the pro-Ubisch bodies show a strong lipidic and scanty glycoprotein and polysaccharide central body; the glycocalyx envelope is formed by a thin neutral polysaccharide layer. At the vacuolate stage, a fibrillar polysaccharide glycocalyx is observed on the tapetum and microspore, the ectexine and endexine are consolidated and the Ubisch bodies have the same pattern as the reticulate and spinulate exine. In ripe pollen, the intine is located, the glycocalyx is faintly contrasted and the veil of lucent pollenkitt is present on the exine. At this stage the staining for lipids, glycoprotein, acid and neutral polysaccharide in the central part of the Ubisch bodies is still marked.