Ontomorphogenesis of summergreen (deciduous) species of the genus Rhododendron L. ex situ

Objective – to study the peculiarities of formation of morphological structures and mechanisms of adaptation to new conditions at the initial stages of ontomorphogenesis of deciduous species of the genus Rhododendron introduced in the M.M. Gryshko National Botanical Garden at the NAS of Ukraine; to identify critical periods and limiting factors at different stages of development of their seedlings under the conditions of primary culture. Material and methods. The object of the study is the introduced deciduous species of the genus Rhododendron (R. albrechtii Maxim., R. canadense (L.) Torr., R. luteum Sweet, R. molle (Blume) G. Don., R. schlippenbachii Maxim., R. vaseyi A. Gray., R. viscosum (L.) Toor.). The study was carried out in 2005–2017 in greenhouse conditions and in areas of department of landscape construction of M.M. Gryshko National Botanical Garden of the NAS of Ukraine according to commonly accepted methods. We used recommendations R.Ya. Kondratovych (1981), A.U. Zarubenko (2006), I.M. Koksheyeva (2009), M.S. Alexandrova (1986), L.V. Vegera (2006) and others. Results. At seed reproduction of studied deciduous species of rhododendrons under ex situ conditions (while providing optimal lighting conditions and humidity in the greenhouse (seedlings, juvenile and immature (1 year old) individuals) and the openground (immature, virginile and young generative individuals)) at the initial stages of ontomorphogenesis, no critical periods were found. Seeds of investigated species have a high germination (90–95 %). The seedlings were characterized by the rapid formation of vegetative organs and by accelerated formation of the generative sphere. Which contributed to the earlier, compared to natural conditions, flowering and the first fruiting. (R. canadense, R. luteum, R. molle, R. molle subsp. japonicum, R. vaseyi). Conclusions. The obtained data testify to the natural (without any abnormal and critical phenomena) progress of the initial stages of ontomorphogenesis in all investigated species of rhododendrons. Growing conditions in greenhouses of the rhododendrons seedlings are required only at the early stages of development (seedlings, juvenile and partially immature individuals (3–10month)). Immature, virginile and young generative individuals under optimal conditions, quite satisfactorily tolerate openground conditions, successfully adapt and produce germinable seeds. That creates the prerequisites for the formation of viable artificial population and for the further selection of resistant to urban environments ecotypes