The Quality and Variability of Morphometric Parameters of Seeds in Dactylorhiza urvilleana (Steudel) Baumann et Kuenkele (Orchidaceae)

The purpose of the study is to analyse the quality and variability of the morphometric parameters of seeds of the same group of Dactylorhiza urvilleana plants, depending on the increase in their calendar age and the year of reproduction. Experimental plants grown from seed (collected in 2009) using in vitro culture. The plants were planted in a permanent place in open ground conditions in the BIN RAS in 2014. Seed studies were carried out from 2015 to 2022. The samples were a mixture of seeds (from 400 and more) from mature fruits of several plants. Morphological analysis of seeds and data documentation were performed using an Axioplan 2 MOT Microscope (Zeiss) with an AxioCam MRc 5 video camera (Zeiss) and Axio-Vision 4.8 software (Zeiss). Microsoft Office Excel 2010 and Statistica 12.0 were used for statistical data processing. In this research, it was revealed that the percentage of fruit set in free pollination ranged from 32 to 48%. Its value in some years was higher than it was noted in the places of natural growth (24-40%). It was shown that the morphometric parameters of the seeds varied significantly in different years of reproduction: the length of the seeds varied from 490.17 ± 6.35 шп to 918.60 ± 15.14 Ltm. the width from 129.73 ± 2.93 Ltm to 220.48 ± 2.97 Ltm. embryo length from 149.56 ± 2.54 Ltm to 251.42 ± 2.15 Ltm. and width from 85.25 ± 1.70 шп to 154.21 ± 1.59 шп. Taking into account the literature data, it was concluded that in D. urvilleana from different places of growth, the length and width of the seeds change in a very wide values range - 2.6 and 2.1 times, respectively. The embryos in the present study were smaller (the length 0.33-0.85 times and the width 0.40-0.96 times) than in seeds from natural habitats in the Krasnodar Krai. However, they were larger than the embryos in the seeds of D. urvilleana from Turkey. The data indicate a high variability of the morphometric parameters of seeds in this species at the population level. It is shown that the sizes of seeds depend on the year of reproduction, the largest sizes were the seeds of 2015 collection, and the smallest in 2021. The share of viable seeds was maximum in 2015 and amounted to 92.9%, and the minimum in 2021 was 43.7%. Although the size of seeds decreased, and the proportion of non-viable seeds increased as the age of the plants increased, this relation cannot be considered definitively proven, since, in recent years, the weather conditions were the least favorable for the development of the studied plants. Comparison of the vegetation rhythm of D. urvilleana plants in open ground conditions at the BIN RAS and weather conditions (average monthly temperature and average monthly precipitation) during the years of study allows concluding that a decrease in seed size and an increase in the proportion of non-viable seeds in 2021 was influenced by high temperature which was combined with a minimum amount of precipitation during flowering and fruit formation (See Fig. 2). The article contains 2 Figures, 2 Tables and 34 References. The authors express their gratitude to A. Pozhidaev for assistance in cultivating plants. The Authors declare no conflict of interest.

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