ИСТИНА

The aperture of the pollen is a thinned or modified region in the pollen wall which is a place of pollen tube germination and it also plays a role in harmomegathic movements. By means of light microscopy in acetolysed pollen with compound apertures we can see a contour of the ectoaperture as a margin of a hole in the ectexine/sexine. The endoaperture is seen as a double contour. The inner contour of the endoaperture forms the margin of the hole where the contours of the ectoaperture and endoaperture cross. Through this hole the pollen tube germination takes place. This place is represented only by the intine in non-acetolysed pollen. The colpus membrane of the ectoaperture margins is underlied by the endexine and intine. The endoaperture margins are framed with the exine and are underlied by the intine. In textbooks the compound aperture is presented as a elongate hole in the ectexine and a hole in the endexine. Both holes cross so that the exine is absent in the crossing. The ectoaperture margins are framed with the endexine and the endoaperture margins are framed with ectexine. The intine is usually not shown on these schemes. But in TEM the ectexine in the aperture region is never underlied by the intine without endexine, and even in monocots there are remnants of the endexine around the aperture. This is evident from ontogenetic studies. In TEM there is always a central hole in the region of colporate aperture where there is no continuous exine. The membrane of the hole is represented only by a considerably thickened intine. The ectoaperture margins have a membrane of a homogeneous endexine and thin intine as seen in TEM sections. The endoaperture margins are thickened and formed by a tapering ectexine, thickened lamellate endexine and gradually thickening intine. Thus, the ectoaperture represents a hole in the ectexine and the ectexine margin can be modified. The ectoaperture membrane is formed by the endexine and intine. The endoaperture is a complex, massive structure. The endoaperture body is represented by a thickened lamellate endexine in the form of a torus with a hole in the center. The outer margin of the endoaperture is a begining of the endexine thickening. The latter can be rather gradual and the outer margin of the endoaperture is unclear. If the thickening starts sharply then the outer margin of the endoaperture is distinct. The aperture in the intine is not a hole, but a thickening of two- or three-layered intine of lens-shape. An accurate conformity is observed of the aperture parts in all sporoderm layers. The hole in the ectexine always overlays the hole in the endoaperture and this “free” space is represented by a thickened stratified intine. Thereby the sporoderm has a considerable thickness and is continuous throughout the pollen but it is represented in aperture and non-aperture regions by different layers with different physicochemical characteristics and functions.