Effects of simulated herbivory on photosynthesis and N resorption efficiency in Quercus pyrenaica Willd. saplings

Abstract

We examined the effects of simulated folivory by caterpillars on photosynthetic parameters and nitrogen (N) resorption efficiency in Quercus pyrenaica saplings. We analyzed the differences between intact leaves in control plants, punched leaves in damaged plants, and intact leaves in damaged plants. We then established two levels of simulated folivory: low (&13% of the leaf area of one main branch removed per plant) and high (&26% of the leaf area of one main branch removed per plant) treatments. No differences were found in net assimilation rate and conductance between either leaf type or treatment during the most favourable period for photosynthesis. However, the N content was lower in punched than in intact leaves, and as a result PNUE was higher in damaged leaves from treated trees. In leaf-litter samples, N mass was significantly higher in punched than in intact leaves in treated plants, and LMA was significantly higher in damaged than in intact leaves of both the treated and control plants. Consequently, N resorption efficiency was around 15% lower in damaged leaves as compared with intact leaves from treated and control plants. Mechanical injury to leaves not only triggered no compensatory photosynthetic response to compensate a lower carbon uptake due to leaf area loss, but also affected the resorption process that characterizes leaf senescence.

Secondary metabolites and nutrients of woody plants in relation to browsing intensity in African savannas

“…Compensatory photosynthesis is expected when sink demand for C is increased, e.g. when root:shoot ratio is increased and shoot growth is stimulated, but accumulating C eventually limits photosynthesis (Fernando et al 2008). Given that photosynthesis depends on N availability, and our plants were not obviously N stressed, we postulate that compensatory photosynthesis is more likely than storage to be the primary source of C in G. flavescens, but this remains to be tested.…”

Trade-offs in plant responses to herbivory influence trophic routes of production in a freshwater wetland

“…Increases in foliar nutrients could not only increase photosynthetic rates of damaged leaves (Nowak and Caldwell 1984;Dyer et al 1991;Oleksyn et al 1998), but could also promote herbivory on leaves with high-nutrient content, introduce rapidly released nutrients from herbivore excrement, or introduce higher quality leaf litter to the detrital food web (Belovsky and Slade 2000;Schmitz 2008). Furthermore, N resorption is reduced in some plants in response to herbivory (Fernando et al 2008), which makes relatively N-rich leaf litter available to decomposers. In this study, %N increased with herbivory intensity in the greenhouse and was greatest in aboveground tissue, which indicates that N. odorata allocated a greater proportion of N aboveground as damage increased.…”

“…To simulate herbivory, a standard hole-punch was used to remove leaf surface area at the time of leaf emergence, restricting holes to the outer leaf margins to prevent puncturing major leaf veins. This method, which has been used successfully for other broad-leaf species (Wold and Marquis 1997;Fernando et al 2008;Pulice and Packer 2008) mimicked what occurs in the Weld. The 5 and 15% values for leaf area removal were selected because they fall within the range observed in the Weld and reported for other Xoating-leaved macrophytes (Lodge 1991).…”

The impact of plant genetic variation and water stress on plant-herbivore interactions

“…Second, as the plant transitions from vegetative growth to sexual and asexual reproduction, resources may be reallocated from leaves to flowers and rhizomes (May & Killingbeck, 1992;Niva et al, 2003). Third, resources may be withdrawn from damaged leaves, including those damaged by herbivores such as lace bugs, and reallocated elsewhere (Fernando et al, 2008;May & Killingbeck, 1995). We hypothesize that in the no-herbivory nitrogen experiment, the plant withdrew resources from leaves during the late August period and allocated those resources to flowers.…”