Population variability of English oak (Quercus robur L.) reproductive organs morphological features in the Forest-Steppe and Steppe of Ukraine

The results of population variability study for English oak (Quercus robur L.) by the peduncle length, its form and the number of acorns on it in Forest-steppe and Steppe are presented. 18 stands of natural and artificial origin (planted forest) in Kharkiv, Poltava, Luhansk, Donetsk and Kirovograd, regions were studied. The stands of natural origin are represented by forest genetic reserves, artificial - mostly forest seed stands. Samples of peduncles were harvested under the crown of trees in the amount of 30-100 pieces (depending on the acorn harvest) in each observed plot. To compare micropopulations by a set of morphological indicators, a graphical method of constructing images of morphotypes in the MS Excel program was used. The levels of intra- and interpopulation variability on all features were determined.The analysis of peduncle length showed that in natural stands of Kharkiv, Donetsk and Luhansk regions dominated trees with peduncle length 2.1-5.0 cm, while in stands of natural origin of Kirovograd region – the trees with peduncle length 5.1-8.0 cm. Any pattern was found in the artificial stands in Kirovograd region. The regional peculiarities regarding the straightness of peduncles were revealed: trees with straight peduncles predominated in the natural stands of Kharkiv region. and in the Kirovograd region – with slightly distorted. Artificial plantations were dominated by trees with straight peduncles (five stands), with a predominance of trees with slightly curved peduncles (two stands) and with an equal share of trees in both groups (one stand). It is found that in the natural stands of Kharkiv and Donetsk regions trees with one acorn on the peduncles predominated, while in the natural stands of Kirovohrad region the frequency of trees with one and two acorns on the peduncles is approximately the same. Most of the artificial stands in the Kirovohrad region were dominated by trees with one acorn on the peduncles.In the vast majority of cases, underdeveloped ovaries are not observed on the peduncles. The share of trees with 1 underdeveloped ovary on the peduncles ranged from 10.0 to 33.3%. The level of intrapopulation variability for all indexes are from high to very high, interpopulation - average.Summarizing the obtained data, it should be noted that natural stands of English oak in Kharkiv, Donetsk and Luhansk regions are characterized by a predominance of trees with relatively short straight peduncles and one acorn on it, while in Kirovograd with medium length with two acorns. An increase in the length of the peduncle and the number of acorns on it in the direction from east to west. Artificial stands are characterized by a higher level of variability in all respects compared to natural.