Experimental Manipulations of Polemonium Foliosissimum: Effects on Subsequent Nectar Production, Seed Production and Growth

Abstract

(1) The carbon budgets of Polemonium foliosissimum individuals were experimentally manipulated. The amount of available carbon was decreased by defoliating 50% of each plant, while available carbon was enhanced by daily watering and by removing either 50% or 100% of the flower buds. (2) Rates of nectar production per flower were constant across all treatments except for a significant increase observed in the watered individuals. (3) There were no consistent changes in average seed set per flower or per plant across treatment groups. (4) Defoliated and control individuals did not differ significantly from one another with respect to average seed weight, but end-of-season underground biomass was significantly less for defoliated plants relative to controls. (5) In the year following treatment, no differences were observed in nectar production per flower, seed production per flower or seed production per plant, although a significant difference in rate of growth was observed. Defoliated plants grew least during the 2-year period, followed by control individuals. The debudded plants increased in size by the greatest margin. (6) The trade-offs between resources allocated to nectar, flowers, seeds and vegetative growth can apparently be expressed in terms of biomass.