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Abstract
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Premise of the study: Investigations of infl orescence architecture offer insight into the evolution of an astounding array of reproductive shoot systems in the angiosperms, as well as the potential to genetically manipulate these branching patterns to improve crop yield and enhance the aesthetics of horticultural species. The diversity of infl orescences in the economically important family Oleaceae was studied from a comparative developmental point of view for the fi rst time, based on species of seven genera ( Chionanthus , Fontanesia , Fraxinus , Jasminum , Ligustrum , Olea , Syringa ). • Methods: Series of developmental stages of chemically fi xed infl orescences were studied with epi-illumination light microscopy. • Key results: All taxa studied have infl orescences with terminal fl owers. The infl orescences are mostly panicles, but in some cases thyrsoids or compound botryoids. Phyllotaxis of the fl ower-subtending bracts is mostly decussate, rarely tricussate ( Fraxinus ) or spiral ( Jasminum ). Accessory fl owers or accessory infl orescences, almost unknown in Oleaceae as yet, were found in two genera. In Syringa , common bract-fl ower primordia are formed by a delay in early bract development compared to fl ower development. Such a delay is also expressed by the loss of bracts in the distal part of infl orescence branches in Syringa and Chionanthus . • Conclusions: Signifi cant variation in branching pattern and phyllotaxy was observed among the studied species of Oleaceae. The suppression of bracts and formation of accessory fl owers were found as special features of infl orescence ontogeny. The occurrence of accessory fl owers and accessory partial infl orescences is interesting from the point of view of dense and fl ower-rich infl orescences in ornamental species.
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