Induced plant resistance and its influence on natural enemy use of plant-derived foods.

In response to herbivory, plants employ several inducible defenses to mitigate herbivore damage. These plant-induced responses can trigger subtle changes in plant metabolite composition, altering the profiles of plant-produced exudates such as (extra-) floral nectar and plant guttation. Natural enemies consume these plant-produced exudates, which serve as consistent and nutrient-dense food sources. There is mounting evidence that natural enemies' access to plant-produced exudates impacts their fitness, performance, and life history traits. Nonetheless, the role of induced plant defense on plant-produced exudates and the subsequent effect on natural enemies remains under-researched. This review, thus, highlights the potential role of induced plant defense on the profiles of plant-produced exudates, with a particular emphasis on altered metabolic changes affecting resource nutritional value and consequently the fitness and performance of natural enemies. Future directions and potential implications in biological control practices are also highlighted.

Functional and ecological consequences of saprotrophic fungus-grazer interactions.

Saprotrophic fungi are key regulators of nutrient cycling in terrestrial ecosystems. They are the primary agents of plant litter decomposition and their hyphal networks, which grow throughout the soil-litter interface, represent highly dynamic channels through which nutrients are readily distributed. By ingesting hyphae and dispersing spores, soil invertebrates, including Arthropoda, Oligochaetae and Nematoda, influence fungal-mediated nutrient distribution within soil. Fungal physiological responses to grazing include changes to hydrolytic enzyme production and respiration rates. These directly affect nutrient mineralisation and the flux of CO(2) between terrestrial and atmospheric pools. Preferential grazing may also exert selective pressures on saprotrophic communities, driving shifts in fungal succession and community composition. These functional and ecological consequences of grazing are intrinsically linked, and influenced by invertebrate grazing intensity. High-intensity grazing often reduces fungal growth and activity, whereas low-intensity grazing can have stimulatory effects. Grazing intensity is directly related to invertebrate abundance, and varies dramatically between species and functional groups. Invertebrate diversity and community composition, therefore, represent key factors determining the functioning of saprotrophic fungal communities and the services they provide.

Effects of carbon dioxide and nitrogen fertilization on phenolic content in Poa annua L.

Different but partially overlapping hypotheses have been developed to predict the allocation of phenolics in elevated atmospheric CO(2). The carbon-nutrient balance hypothesis predicts increased allocation to phenolics due to reduced relative availability of nitrogen. The growth-differentiation balance hypothesis states that allocation will depend on source and sink strength, while the protein competition model predicts that allocation will remain unchanged. We grew Poa annua at two CO(2) concentrations in soils of three different nutrient levels. Although plant-tissue nitrogen levels were reduced in high CO(2) and photosynthetic rate increased, phenolic concentration and biomass allocation remained unchanged. We discuss these data in the context of the three models' predictions of phenolic allocation in conditions of elevated CO(2).