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The generic complex Robinia L. is of great interest for the mobilization of genetic resources in arid regions of Europe, Asia and North America. The different rates of expansion of the cultigenic ranges of some species of the genus Robinia L. are undoubtedly related to the peculiarities of their adaptation and life strategies for survival in the new conditions of existence.
In this regard, the purpose of this work was to analyze the mechanisms of adaptation and life strategies of various species of the genus Robinia in the conditions of introduction.
The objects of research were the species and forms of the genus Robinia L.: R. neomexicana Gray. (syn. Robinia luxurians (Dieck.) C. K. Shneid.); R. pseudo-acacia L.; R. pseudoacacia f. pyramidalis (Pepin) Rehd.; R. pseudoacacia f. um-braculifera (DC) Rehd.; Robinia viscosa Vent. var. hartwegii (Koehne) Ashe growing in cluster collection sites of the Federal research CENTER of Agroecology of the Russian Academy of Sciences, cadastre №34:34:000000:122, 34:34:060061:10.
The conducted research has revealed a number of phylogenetic adaptations in various representatives of the genus Robinia L. to the impact of adverse environmental factors, such as a highly branched root system, xeromorphic structure of leaves, openwork and wind resistance of crowns, the ability to tolerate prolonged droughts, and symbiotic relationships with nitrogen-fixing bacteria.
Research results have shown that all species of the genus Robinia L. use a number of phenotypic ontogenetic adaptations during introduction. The most important of them are the change of life form (tree-shrub, single - trunk-multi-trunk tree), as well as a decrease in growth rates and a decrease in the overall height of plants, depending on soil fertility, moisture supply and the damaging effects of low winter temperatures. Thus, on ordinary chernozems in Ukraine at the age of 20 years, plantings from Robinia pseudo-acacia reach a height of 14-15 m, while on light chestnut soils in the Lower Volga region at the same age they reach only 6 m.
In addition, over the past centuries, representatives of the genus Robinia L. have developed a number of genotypic adaptations to new conditions of existence. These adaptations are one of the most important, since they lead to the appearance of qualitatively new adaptations that expand the boundaries of ecological plasticity of the species. Seasonal cycles of phenological development have been reduced in all species and they are currently being developed at the optimal time for the development of tree introducers in regions with a relatively harsh climate for them. According to the indicator of phenological atypicity in the Lower Volga region, they are in the lower half of the normal range (from +1 to 0) for the implementation of phenological phases, which indicates that the cycle of their development has been successfully adapted and corresponds to the vegetation period of the place of introduction. According to our research, all species of the genus Robinia L. have crossed the temperature threshold of-37°C during acclimatization.
The genotypic nature of the formed adaptations to low winter temperatures is proved by a comparative analysis of the literature data on frost resistance of various species of the genus Robinia L. obtained at the beginning of the XX century with data from visual and physiological assessment methods conducted over the past decades. The second important evidence for the appearance of adaptations fixed at the genetic level is the difference in hardiness between the forms of R. pseudoacacia f. pyra-midalis (Pepin) Rehd., R. pseudoacacia f. umbraculifera (DC) Rehd. and typical representatives of R. pseudoacacia L. The absence of genetic heterogeneity in the vegetative reproduction of these forms stopped the processes of microevolution, not allowing them to adapt to the new conditions of existence.
Analysis of life (environmental) strategies has shown that in growing communities of Robinia, pseudo-activity can equally successfully act as a patent or an explerent. At the same time, its vialent properties are much less pronounced. The analysis of R/K survival strategies allows us to attribute it to r-species with high generative potential, short juvenile and virginal stages of development, and the ability to naturalize. However, under optimal conditions of existence in the absence of competition, it, like many K-species, can reach a significant age of up to 400 years.
All species of the genus Robinia L. are capable of naturalization in certain regions of the secondary range. However, the record holder for this indicator is undoubtedly Robinia pseudo-acacia. In our opinion, this fact is due to the high generative potential of R. pseudoacacia L. in relation to related species and its high economic significance for the purposes of forest protection breeding. Representatives of the genus Robinia L. they do not have devices for active propagation of seeds over significant distances. Naturalization (entering natural vegetation communities) usually occurs in the immediate vicinity of artificial forest protection stands. Pink-flowered species of the genus Ro-binia L., due to their small growth, are not of particular interest for agroforestry purposes. These species are usually used in landscaping localities as ornamental plants. Artificial territorial isolation from natural plant communities and relatively low generative potential do not allow them to actively display their Inva-sive properties.
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