Biometric indicators of pollen and growth characteristics of pollen tubes of Juniperus deltoides R. P. Adams in mountain Crimea

The process the organism individual development implies its adaptation, the patterns and principles of which, among other things, are reflected in the implementation of the male gametophyte. The forest stand natural renewal primarily depends on the indicators of the seed formation success, determined among other things by the pollen characteristics. For species threatened with extinction the problem of renewal stability is especially acute. The paper is aimed to determine the biometric characteristics and the viability level of J. deltoides’s pollen grains in the Mountainous Crimea. In that regard, the following tasks were set: to determine the morphometric parameters of J. deltoides pollen grains, to assess their potential and real viability, and to identify the degree of environmental factors influence on the development of the male reproductive system of J. deltoides in the Mountainous Crimea. Within each trial area, 10 model trees were identified to collect their pollen grains during the flight period. The diameter of pollen grains in two mutually perpendicular planes was measured on temporary acetocarmine preparations. Pollen germination was carried out using the hanging drop method. A new methodology was developed to determine the integral assessment of pollen quality, including a comprehensive analysis of its histochemical and morphological features characterizing viability. The sizes of J. deltoides pollen grains in Mountainous Crimea differ within the error limits. The average diameter of fertile pollen for the species, under the conditions of the peninsula, is 27.08 ± 0.49 μm. The average percentage of fertile (colored) pollen is 55.19 ± 3.84%. At the beginning of the 21st century, this figure ranged from 87.1% to 98.2%. It can be assumed that within the past two decades, the amount of fertile pollen has decreased by 1.7 times. The greatest influence on the fertility of J. deltoides pollen is almost equally exerted by the altitude above sea level and the edaphic conditions of the places of growth of individuals (6.38% and 6.50%, respectively). During the integral assessment of the pollen quality of the Crimean population of J. deltoides, it was found that the overwhelming majority of individuals (64.71%) are characterized by good quality pollen grains. The proportion of germinated pollen of J. deltoides in Mountainous Crimea is low and amounts to 20.16±1.12%. The main factor influencing the viability of pollen grains is the anthropogenic load of the territory (the strength of influence is 51.63%). The average proportion of germinated pollen in significantly anthropogenically disturbed areas is 12.0±1.26%, which is 2.3 times lower than that of individuals growing in undisturbed areas.