Resorption of trap nitrogen during senescence and the benefit of prey capture in the carnivorous plant, Sarracenia alata

Abstract

Carnivorous plants commit a certain quantity of nutrients to their traps, so in order to break even, the quantity of limiting nutrients acquired from prey capture should at least equal the quantity committed to the trap. However, nutrient resorption during senescence could substantially reduce the quantity of nutrients irretrievably committed to traps and affect the benefit of prey capture. Since carnivorous plants generally grow in nutrient-poor soils, we hypothesized that nitrogen resorption during senescence should be relatively efficient. We further hypothesized that the resorption of nitrogen should reduce the nitrogen irretrievably committed to the trap, which in turn would minimize the N needed from prey capture in order to break even. We performed a field study in Leon County, TX, USA in which we compared the N content of non-capturing mature pitchers, of non-capturing senescent pitchers after resorption, and of prey capture in Sarracenia alata. The observed N resorption efficiency of S. alata in this study was 38–42 %, based on dry-mass-corrected %N or N/unit area, respectively. This resorption efficiency was low compared to quantities reported in other carnivorous plant species and did not support our first hypothesis. The N content of cumulative prey capture was not sufficient to offset the N content of mature pitchers but was sufficient to offset the N contained in senescent pitchers. Therefore, resorption reduced the N required from prey capture to break even, which supported our second hypothesis.