Reproductive biology studies towards the conservation of two rare species of Colchic flora, Arbutus andrachne and Osmanthus decorus

Abstract

Our study examines the structural peculiarities of the generative sphere at different phases of development, and the processes of pollination, fertilisation, and seed formation in 2 species of wild flora: Arbutus andrachne L. (Ericaceae), the eastern strawberry tree, and Osmanthus decorus (Boiss. & Balansa) Kasapligil (Oleaceae), Caucasian osmanthus. These Arcto-Tertiary plants are included in the Red Data Book of the Georgian SSR. As germinable seeds are the main factor determining species distribution and the complete transfer of genetic information, the aim of our research was to establish the self-regeneration capacity of the species under study and choose optimum conditions for seed germination, the further development of seedlings, and their ex situ conservation. It has been stated that abnormalities taking place at different stages of sexual reproduction are responsible for the low capacity for seed formation found in the studied species. In particular, these factors are as follows: a limited capacity for allogamy; a low percentage of pollen tube development, at 20%-30% for Arbutus andrachne and 15%-20% for Osmanthus decorus, despite the high fertility of pollen grain of both species (approximately 70%-80%); and the frequent occurrence of embryo degeneration. The germination of Arbutus andrachne seeds on petri dishes on agar reached 80%. The results of the present study allow for the elaboration of protocol for the propagation of these relic species and for their further ex situ conservation on the collection plot of the Department of Plant Conservation.