Original article

Abstract – Zygotic embryo development and its influence on empty seed formation of the European larch (Larix decidua Mill.) was studied within a seed orchard in the Slovak Republic. Histological study revealed a fertilization date early June. Although embryogenesis was most intensive in June, fully morphologically differentiated embryos were observed no earlier than in the second half of July. Multiple fertilization and simple polyembryony were relatively rare but their frequencies correlated with the efficiency of pollination. Only a small percentage of developing embryos reached full maturity. Degeneration included suppressed embryos from polyembryony as well as normal embryos occupying the optimal position within the corrosion cavity of the female gametophyte. The mean proportion of fertilized ovules without a viable embryo was 61 % after open pollination and as high as 88 % after controlled selfing. In total, embryo degeneration reduced the potential full seed percentage by almost 40 % and is therefore considered the most important cause of unsound seed development in European larch. larch / embryo / embryogenesis / empty seed Résumé – Embryogenèse zygotique et formation des graines vides chez le mélèze d’Europe (Larix decidua Mill.). Le développement des embryons zygotiques et son influence sur la formation des graines vides du mélèze d’Europe (Larix decidua Mill.) ont été observés en condition de verger à graines en République Slovaque. L’étude histologique révèle que la période de fécondation la plus fréquente est le début du mois de juin. Bien que l’embryogenèse soit la plus intensive en juin, les embryons morphologiquement les plus différenciés sont observés dans la deuxième moitié du mois de juillet. Même si la fécondation multiple et la polyembryonie simple sont relativement rares, elles sont corrélée