Exploring the Pollen Fertility Estimationof Selected Taxa of Boraginaceae from Pakistan

This is the authors' abstract. We don't add key points for this paper.

This research aimed to evaluate the pollen fertility and micromorphology of Boraginaceae species across Pakistan, with an emphasis on how population size influences reproduction. A total of 27 species of the Boraginaceae family were collected from Pakistan, and light microscopy was used to examine pollen parameters, including size, shape, exine thickness, and fertility percentage. The findings revealed a range of pollen shapes, including prolate, prolate-spheroidal, sub-prolate, oblate, sub-oblate, and oblate-spheroidal, with oblate and sub-oblate being the most frequent. Exine thickness varied significantly among species, with Alkanna tinctoria having the thickest exine (2.80 μm), while Onosma hispida exhibited the thinnest exine (0.75 μm). These variations in pollen shapes and exine thickness play a crucial role in species identification and may influence reproductive success, as thicker exines offer structural protection against UV radiation, desiccation, and microbial attack, enhancing pollen survival during pollination. Fertility rates also varied, with Trichodesma indicum exhibiting the highest pollen fertility rate (94.94%), whereas Arnebia hispidissima had the lowest (60.50%) with an average fertility of 78.83% across the species. Larger populations exhibited higher pollen viability, while small, isolated populations had reduced fertility, demonstrating the significant effect of population size on reproduction. This study uncovers previously undocumented pollen fertility and morphology differences among Boraginaceae species in Pakistan, adding valuable information to current knowledge and emphasizing elements that influence reproductive success.