Ecology of two cytotypes ofButomus umbellatus II. Reproduction,growth and biomass production

Generative and vegetative reproduction of diploid and triploidButomus umbellatus L., and growth and biomass production of both cytotypes under 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 experimental garden. Both cytotypes do not differ in seed germination and seedling survival. Triploids produce more aboveground and underground biomass, more numerous lateral rhizome buds, and have significantly higher flowering stalks. Low generative reproduction (limited seed production) in triploids is compensated for by more intensive vegetative reproduction. High nutrient level appeared to be stressful for plants of both cytotypes: it limits plant growth and causes plant mortality. Triploids are more viable than diploids in this case, which may be important for their survival under conditions of high trophic level.