Abstract
Pollination and fertilization are the most important and responsible stages in sexual reproduction of coniferous plants. The period of high concentrations of juniper pollen in overhead during pollination period is no more than 4–6 hours and within one calendar day. This dependence remains invariable from year to year, and does not depend neither from weather conditions, nor the peculiarities of the place where juniper grows. Influence of external agents on dynamics of exudation of a juniper pollination droplet is studied. The duration of exudation and volume of secretory liquid exuded by tissues of ovules during the period of prescription in the juniper depend from presence of external agents on a surface of pollination droplet, their sizes and physical and chemical properties. The pollination droplet chemical compound is studied. In sugars composition of juniper pollination droplet there are only two monosaccharides: glucose and galactose. the amino acids composition is prevailed by arginine, aspartic and glutamic acids. The results of the studies confirm complex chemical composition and multifunctionality of juniper pollination droplet. The pollination mechanism of juniper is effective and selective. The morphological structure of pollen grains of juniper predetermines the processes of pollen germination at early stages. The hydrophilic capsule, formed pollen hydration, promotes to exine rupture and shedding. This capsule remains until the fertilization. The distal tip of pollen tube remains in itduring all time of its growth. In culture in vitro development of pollen tubes of juniper proceeds non-uniformly. At definition of juniper pollen viability it is necessary to consider a stage of pollen tubes development.
Highlights
The extensive bibliography which is generalized in a number of reviews is devoted to the problem of pollination in Gymnosperms (Doyle 1945; McWilliam 1958; Owens et al 1987, 1998; Anderson and Owens, 2000)
The most important of these factors are: the volumes of produced pollen, the terms of disclosing of a microsporangium, the duration of the period of pollen dispersion, the weather conditions during the pollination period, the time of days in which there is a mass departure of pollen and connected with it the ascending both descending streams of air and turbulence, aerodynamic properties of pollen grains, efficiency of mechanisms of pollen catching by receptive ovules
Pollen dispersion regime in natural populations of a juniper studied in northern taiga (Arkhangelsk region) in 2007–2016. This regime in juniper populations differs from the general scheme of a pollen dispersion regime in populations of main forestry coniferous species at which the total duration of the pollination period can be stretched for some weeks and for which the sinusoidal type of a curve of distribution of density of a pollen stream with maxima in midday and minima at night is characteristic
Summary
The extensive bibliography which is generalized in a number of reviews is devoted to the problem of pollination in Gymnosperms (Doyle 1945; McWilliam 1958; Owens et al 1987, 1998; Anderson and Owens, 2000). The functional properties of pollination droplet of coniferous species were discussed in works of number of authors (Gelbart and von Aderkas 2002; Poulis et al 2005; Mugnaini et al 2007b; Wagner et al 2007; Nepi et al 2009). The success of pollination in anemophilous coniferous species is caused by many factors. The most important of these factors are: the volumes of produced pollen, the terms of disclosing of a microsporangium, the duration of the period of pollen dispersion, the weather conditions during the pollination period, the time of days in which there is a mass departure of pollen and connected with it the ascending both descending streams of air and turbulence, aerodynamic properties of pollen grains, efficiency of mechanisms of pollen catching by receptive ovules.
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