Buyun L. Tropical orchids (Orchidaceae Juss.) : reproductive biology, structural and functional adaptations, ex situ conservation

The thesis is devoted to the investigation of reproductive biology of tropical orchids as well as the elucidation of structural and functional adaptations of these plants under glasshouse conditions. The impact of different factors including breeding systems, pollination strategies, flowering longevity by pollination, pollinated flower position in inflorescences, resource status on reproductive success of orchid species ex situ has been analysed. For accessing ecological specialization of seeds of different species, intra- and interspecific variability of seed dimensions, seed heterogeneity within particular fruit, the morphometric methods of investigation have been used. The adaptive potential of the selected species of orchid plants under glasshouse conditions as well as their in vitro cultures has been evaluated. The malondialdehyde (MDA) content and superoxide dismutase (SOD) activities have been proposed to be used as the early stress markers to access the stress development, particularly under low temperature, in orchids of different ecological groups and to estimate the tolerance limits to in vitro to ex vitro conditions change. Based on the results of comparative anatomical stomatographic analysis of the leaf surfaces of nine orchid species in vivo and in vitro, distinctive patterns of the epidermal structure of juvenile plants (stomata density/mm2, stomatal index, epidermal cells number/mm2) were revealed; accordingly with the patterns of leaf surface, the criteria for predicting the acclimatization success of in vitro propagated seedlings to ex vitro conditions have been proposed. It was shown that abnormal anatomy of orchid seedlings in vitro propagated plants (malformed stomata, discontinuing cuticle layer, twin stomata) correlate with poor survival and acclimatization of ex vitro. On the basis of the seed coat micromorphology studied with scanning electron microscopy (SEM) and seed morphometry made with light microscopy, the trends of ecological specialization of the orchid seeds have been defined. For the first time, the chromatographic profiles of orchid seed endometabolites as well as alellopathic activities of 10 orchid species belonging to different ecological groups have been investigated from the viewpoint of the orchid-mycobiont relationships. The results of the integrated experimental research of tropical orchids ex situ and data of the author's observations in situ have been analysed from the standpoint of life history strategies.