Pollen grains are produced during meiosis (microsporogenesis), in the anthers of flower buds. Apertures are usually formed at the last points of contact between the microspores. However this mechanism is not universal, and cannot explain aperture determination in species with more apertures than there are points of contact. Here, we study pollen development in pantoporate species (multi-aperturate) to understand what mechanism could account for aperture determination in this case. Twelve species producing pantoporate pollen were collected. They represent both monocots and eudicots. Microsporogenesis in these species was observed using epifluorescence microscopy with aniline blue coloration, which enabled us to observe callose. The features of microsporogenesis (cytokinesis, intersporal wall formation and tetrad form) in species with pantoporate grains do not differ strongly from the standard developmental pathway in monocots and eudicots, although tetrad form is more variable in pantoporate species. We identified additional callose deposits in microspores after the formation of the callose walls within tetrad, correlated with subsequent aperture position of the pollen grain. The number, relative size and density of these deposits are similar to those of the apertures in mature pollen grains. Additional callose deposits are likely to be involved in aperture determination, although the precise cellular mechanism of their involvement is not yet understood. Such callose deposits are present in phylogenetically distant species, suggesting that they have appeared several times independently in angiosperms.

花粉粒在减数分裂（小孢子发生）过程中在花蕾的花药中产生。通常在小孢子之间的最后接触点形成孔。但是，这种机制不是通用的，并且无法解释在具有比接触点更多的孔的物种中进行孔确定。在这里，我们研究了潘托普尔物种（多孔）中的花粉发育，以了解在这种情况下哪种机制可以解释孔径的确定。收集了十二种产生全花粉的花粉。它们代表单子叶植物和双子叶植物。使用带有苯胺蓝颜色的落射荧光显微镜观察了这些物种中的微孢子发生，这使我们能够观察call。小孢子发生的特征（胞质分裂，尽管在四倍体的物种中，四倍体的形态变化更大，但具有五倍体的谷粒的物种之间的胞间壁形成和四倍体形式与单子叶植物和双子叶植物的标准发育途径没有很大的不同。我们在四分体内形成ose质壁后，在小孢子中鉴定出了更多的call质沉积物，与随后的花粉粒孔径位置相关。这些沉积物的数量，相对大小和密度与成熟花粉粒中的孔的数量，相对大小和密度相似。尽管还不清楚其参与的确切细胞机制，但其他的愈伤组织沉积物可能与孔径确定有关。这类愈伤组织沉积物存在于系统发育距离较远的物种中，表明它们已在被子植物中独立出现过几次。