The cost of flowers in Nigella degenii inferred from flower and perianth removal experiments

I examined the costs of producing and maintaining floral structures in Nigella degenii (Ranunculaceae). To test for such costs, I subjected plants of two populations to flower or perianth removal and then evaluated allocation to subsequently produced flowers, fruits, and seeds. Based on data from a flower removal experiment, the amount of resources allocated to flowers during the staminate and pistillate stages was about half as great as the amount of resources devoted to fruit maturation. Plants on which the perianths were removed at the bud stage produced more flowers or had a higher percent fruit set and seed viability than did plants from which the perianths were removed immediately after the growth of the sepals and petals. Removal of fully developed perianths at the onset of flowering increased flower number, fruit set, or seed viability relative to plants on which the perianths remained until senescence. Some of these effects were population specific, but plants in low and high watering treatments responded similarly to perianth removal. Given these observations, I propose that the costs of producing and maintaining floral structures represent a significant drain on the water and/or energy budget of a N. degenii plant and that some trade-offs may be specific to the population in which they have been detected.