Androdioecy (the coexistence of two genders, cosexuals and males, in a single population) is a rare breeding system. In terms of functional gamete production, androdioecy has been reported in a small number of windpollinated and insect-pollinated species. In this study we examine the floral biology, stability of gender, and fruit and seed production after self-pollination and outcrossing pollination in a potentially androdioecious tree, Fraxinus ornus, in southern France. Individual trees have either hermaphrodite flowers or male flowers, the latter lacking a well-developed gynoecium. The two genders produce morphologically similar pollen and were present in 1 : 1 or slightly male-biased ratios. Only hermaphrodites set fruit during 2-4 yr of observation at four different sites in southern France. Experimental pollinations of eight trees in two different sites showed that hermaphrodites produce viable pollen in dehiscent anthers and viable seeds. Thus, in terms of functional gamete production, F. ornus is a new case of functional androdioecy. Seven hermaphrodites were self-compatible, and such self-compatibility of hermaphrodites might improve the colonizing ability of F. ornus in a region where this species is actively expanding its range.
Résumé.-L'étude porte sur six taxons du genre Mentha (3 espèces et 2 hybrides dont deux formes pour l'un de ces derniers). A quelques différences quantitatives près, les résultats sont comparables pour les différents taxons. La cu~ure d'apex (méristème plus la dernière paire d'ébauches foliaires), ainsi que le microbouturage ont été mis au point. Une méthode de mu~iplication in vitro des menthes alliant les avantages de ces deux techniques est proposée en tenant compte de l'origine des bourgeons (axillaires ou néoformés sur cal) produisant les nouvelles générations de microboutures.Summary.-The study concerns 6 taxa of the Mentha ge nus (3 species and 2 hybrids with 2 forma for one of these lasts). Sorne quantitative difference apart, the results are comparable in the various taxa. The apex culture (stem meristem with the last leal primordia) and the microcutting technics was achieved. An in vitro multiplication method of minis, combining the advantages of these two technics is proposed baking notice of the origin (axillary or neoformed on callus) of the buds producing the new microcutting generation.
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