PS 43-135
Nitrogen resorption and the benefit of prey capture in the carnivorous plant, Sarracenia alata
Nutrient resorption during senescence could substantially alleviate the nutrient cost of constructing carnivorous structures in carnivorous plants, but cost-benefit studies of prey capture have rarely examined nutrient resorption. Sarracenia alata is a carnivorous pitcher plant that supplements nitrogen (N) acquired from nutrient-poor soil with N from insect prey. The purpose of this study was to examine the effect of nitrogen resorption on the nitrogen cost-benefit analysis of prey capture in a carnivorous plant.
Fieldwork was conducted at a bog located near Buffalo, TX. Twelve five-meter transects were established throughout the bog. Within each transect, a young, newly opened pitcher was selected approximately every half meter (10 pitchers per transect, 120 pitchers total). Pitchers were haphazardly assigned to one of three treatments: N content of prey capture, N content of non-capturing mature pitchers, and N content of non-capturing pitchers after translocation. The openings of pitchers in the latter two treatments were occluded with cotton to prevent prey capture. Nitrogen contents of dried, ground samples were analyzed. Benefit was estimated by measuring the total N in captured prey. Nitrogen cost was estimated two ways: N content of non-capturing mature pitchers and N content of non-capturing pitchers after translocation.
Results/Conclusions
The cumulative N in prey capture (1.75mg + 0.89) was less than the average N content of mature pitchers (2.61mg + 0.42, mean + SE), although the difference was not statistically significantly (P > 0.05). Therefore, the cumulative N in insect capture was slightly less than, or approximately equal to, the average N content of mature pitchers.
The N remaining in non-capturing pitchers after senescence represents the quantity of N originally allocated to pitcher construction that cannot be recovered. The mean N in pitcher tissue after translocation was 0.002mg + 0.0004, reflecting a resorption efficiency of over 99%. This resorption efficiency is higher than any previously reported. Because of the high efficiency of resorption of N allocated to pitcher production, virtually all N provided by prey capture can be considered a net gain.