Ellison Abstract- 2008 Farnsworth and Ellison

Farnsworth, E. J., and A. M. Ellison. 2008. Prey availability directly affects physiology, growth, nutrient allocation, and scaling relationships among leaf traits in ten carnivorous plant species. Journal of Ecology 96: 213-221.

Abstract 

1. Scaling relationships among photosynthetic rates, leaf mass per unit area (LMA), and foliar nitrogen (N) and phosphorus (P) content hold across a diverse spectrum of plant species. Carnivorous plants depart from this spectrum because they dedicate substantial leaf area to capturing prey, from which they derive N and P. We conducted a manipulative feeding experiment to test whether scaling relationships of carnivorous plant leaf traits become more similar to those of non-carnivorous taxa when nutrients are not limiting.
2. We examined the effects of prey availability on mass-based maximum photosynthetic rate (A_mass), chlorophyll fluorescence, foliar nutrient and chlorophyll content, and relative growth rate of ten Sarracenia species. We hypothesized that increased prey intake would stimulate Amass, reduce stress-related chlorophyll fluorescence, increase photosynthetic nutrient-use efficiencies (PNUE_N, PNUE_P), and increase relative biomass allocation to photosynthetically efficient, non-carnivorous phyllodes.
3. Two plants per species were assigned in a regression design to one of six weekly feedings of finely ground wasps: 0 – 0.25g for small plant species; 0 – 0.5g for intermediate-sized species; and 0 – 1.0g for large species. The first two leaves emerging on each plant were fed.
4. Increased prey availability increased photosystem efficiency (F_v/F_m ratio) in the first two leaves, and chlorophyll content and A_mass in younger leaves as older leaves rapidly translocated nutrients to growing tissues. Higher prey inputs also led to lower N:P ratios and a shift from P- to N-limitation in younger leaves. PNUE_P was significantly enhanced whilst PNUE_N was not. Better-fed plants grew faster and produced a significantly higher proportion of phyllodes than controls.
5. Feeding shifted scaling relationships of P relative to A_mass, N, and LMA from outside the third bivariate quartile to within the 50th bivariate percentile of the universal spectrum of leaf traits; other scaling relationships were unaffected. Carnivorous plants can rapidly reallocate P when nutrients are plentiful, but appear to be less flexible in terms of N allocation.
6. Synthesis: Our results support the general hypothesis put forward by Shipley et al. (2006) that observed scaling relationships amongst leaf traits derive from trade-offs in allocation to structural tissues versus liquid-phase (e.g., photosynthetic) processes. These trade-offs appear to be especially constraining for plants growing in extremely nutrient-poor habitats such as bogs and other wetlands.

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