Pollen Morphology of Broadleaf Trees Growing in Different Health Conditions in the City of Aktobe

Various characteristics of plant organs and pollen contribute to biological diversity (Hwang and Masters, 2013) and data on their variability lay groundwork for the solution of many biological problems related to taxonomy, microevolutionary processes, hybridization, and gene pool protection (Polyakova and Gataulina, 2008; Warny, 2013). Pollen analysis or the study of pollen grain morphology (i.e., size, exine pattern, fertility, and viability) is a research method for measuring the reproductive potential of plants (Goodman et al., 2015). Pollen analysis deals with the estimation of normal and defective pollen fractions and with metabolism processes in pollen grains (Pausheva, 1980; Riley et al., 2015). The problem of multiple anomalies in pollen grains has been a forefront in recent debates (Augenstein, 2016; Miroff, 2019). The quality of pollen grains is crucial to the reproductive biology of plants and their ability to generate full-fledged seeds (Laurence, 2018; Laurence and Bryant, 2019). Normally, pollen in plants growing under normal conditions is of good quality and the amount of normal pollen grains is close to 100% (Bryant and Bryant, 2019). Increased pollution, on the contrary, can reduce their proportion (Ashikhmina, 2005). Recent decades have saw a steady growth in various sectors of economy, which strengthened the role of anthropogenic factors, both biotic and abiotic (Legendre and Legendre, 2012). Cities with industrial zones functioning side by side with the green zones can serve a convenient model object in the judgment of pollution levels. Such cities can be found in many countries around the world, including China, Kazakhstan, Russia, and the United States. At the same time, the Western European countries have a strong experience in designing urban landscapes with ecological considerations in mind, something that developing countries, such as Kazakhstan, may need to consider. The widely used landscape plants are metal tolerant, mostly woody, such as the black poplar (Populus nigra L.). The most solid and gas emissions concentrate in the air 15 to 20 m above the ground. This range of polluted air travel is the living zone for humans and most plant species (Ferguson et al., 2018). Therefore, research on the effective monitoring of pollutants in green zones is needed (Faucon et al., 2017). This study chose plant pollen as a research object for its sensitivity to pollution and anthropogenic loads of different intensity. This kind of data is somewhat scarce, which defined the relevance of this study. It is known that pollen formation takes place through many cell divisions, which vary among different plant species (He et al., 2019). This statement equally applies to pol-