The effect of reproduction on nitrogen use-efficiency of three species of the carnivorous genus Pinguicula

1 Life history theory predicts that reproduction incurs costs in terms of f uture growth and survival. In infertile environments reproductive events ma y accelerate nutrient turnover such that losses of limiting nutrients canno t be replenished by uptake from the soil. 2 We compared the effect of reproduction on nitrogen (N) turnover and N use -efficiency, i.e. the annual dry matter produced per unit N lost, of three carnivorous species of the genus Pinguicula on an infertile subarctic heath . We hypothesized that reproduction should increase N turnover, unless a la rger N pool or improved N resorption can compensate for the losses associat ed with reproduction. 3 These carnivorous herbs showed a nitrogen use strategy similar to that of non-carnivorous plants (herbs and grasses) with a relatively low mean resi dence time (MRT) of N and a large dry matter productivity per unit N in the plant (annual N productivity). N pool size and the efficiency of N resorpt ion from senescent leaves were similar in reproductive and non-reproductive individuals. Reproductive individuals had significantly larger annual N lo sses and thus a lower average MRT (0.8 vs. 1.8 years), with values < 1 indi cating that the annual N losses are greater than the annual average N pool. Unless plants can enhance their nutrient acquisition, flowering may theref ore impact on future growth and survival. 4 This study presents evidence for a direct link between reproduction, refl ected in a higher relative allocation to inflorescences, turnover and N use -efficiency; the latter being reduced because of increased N turnover. The ranking of species in terms of reproductive allocation was the reverse of t heir ranking in terms of their N use-efficiency.