ECOLOGY OF 2 CYTOTYPES OF BUTOMUS-UMBELLATUS .2. REPRODUCTION, GROWTHAND BIOMASS PRODUCTION

Generative and vegetative reproduction of diploid and triploid Butomus umbellatus L., and growth and biomass production of both cytotypes un der two different nutrient levels were compared. Seedling survival was studied under controlled conditions in a growth chamber; the response of plants to different nutrient conditions was studied in experimenta l garden. Both cytotypes do not differ in seed germination and seedlin g survival. Triploids produce more aboveground and underground biomass , more numerous lateral rhizome buds, and have significantly higher fl owering stalks. Low generative reproduction (limited seed production) in triploids is compensated for by more intensive vegetative reproduct ion. High nutrient level appeared to be stressful for plants of both c ytotypes: it limits plant groWth and causes plant mortality. Triploids are more viable than diploids in this case, which may be important fo r their survival under conditions of high trophic level.