Інтродукція Рослин (May 2018)
Peculiarities of seasonal dynamics of water-exchange processes in species of Populus L. in dendrarium of Kryvyi Rih Botanical Garden
Abstract
Objective – to investigate the features of waterexchange processes in the assimilation apparatus of poplars introduced in Dendrarium of Kryvyi Rih Botanical Garden of the NAS of Ukraine. Material and methods. The object of the research were changes in the state of the water regime (waterlogging, water deficiency, water retention capacity) of poplars, introduced in Dendrarium of Kryvyi Rih Botanical Garden of the NAS of Ukraine. The studies were carried out on the following poplar species: Populus italica Du Roi, P. deltoides W. Bartram ex Marshall, P. simonii Carriére, P. candicans Aiton, P. bolleana Carriére. The species involved in the experiment are represented by individuals of the second class of age (up to 20 years). Determination of bound and free water in the plant material was carried out by refractometric method according to N.A. Gusev (1960). The total amount of water, water retention capacity and water deficiency of poplar assimilation apparatus was determined according to the generally accepted methods in bio logy (Bessonova, 2006). In experiment we used leaves of plants selected from the middle part of the crown of the southwestern exposure. Results. The total water content of leaves of P. bolleana and P. italica in June was 20–40 % greater than in P. deltoides, P. simonii and P. candicans. From June to September, the water content of the poplar species under study decreased. The most significant decrease in the total water content in poplar leaves (by 15–20 %) in comparison with June is noted in P. deltoides, P. simonii and P. sandicans whose natural range is the more humid places (North America and the Far East). At the same time, the total waterlogging in the Central Asian species of P. bolleana and P. italica decreased to 10 %. From June till August, the free water content decreased and the content of bound water increased. P. italica and P. bolleana of bound water are in 1.1–1.2 times larger than in P. candicans, P. deltoides and P. simonii, which indicates a greater fitness of the first to drought. In August in all poplars studied the water deficit index exceeded the safe value of 10 % and fluctuated within 10.4–19.1 %. The largest water deficiency was in poplars, which naturally grow in more humid areas with moderate temperatures – P. simonii, P. candicans and P. deltoides, which is in 2.0–2.5 times more than in early summer. The smallest water deficit during vegetation was detected P. bolleana and P. italica, in which this index increased by an average in 1.6 times. The highest indicators of water holding capacity in poplars were in June. The higher water retention capacity of the leaves in P. bolleana and P. italica allows poplars to resist dehydration under unfavorable conditions and is an indicator of their adaptation to the conditions of growth. Conclusion. The most resistant to unfavorable conditions of moistening are P. bolleana and P. italica, in which the ratio of water exchange processes is at optimal level, which is ensured by the agreement of high water content of cells, low values and tendency to decrease the daily water deficit during vegetation, to a partial restoration of the waterlogging of tissues when the effect of the stress factor is weakened.
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