The mutual effect of nutrients on plant–herbivore interactions

Nutrients contained in plant tissues serve as the driving force behind plant and herbivore interactions. The nutrient level, including different kinds of elements and amount of fertilizer, can vary owing to variations in soil composition and this can directly impact plant defense response against herbivores. Plants take up nutrients via two pathways: (i) directly through the root hairs and epidermis and (ii) indirectly through the beneficial microbes that interact with plant roots, such as mycorrhizal fungi and rhizobacteria. The associated microbes, modifying plant nutrient composition, can indirectly affect plant and herbivore interactions. These direct and indirect nutrient uptake pathways adjust plant resistance or tolerance to herbivore attack, as evidenced by factors such as herbivore performance, plant nutrient status, biomass allocation, and compensatory growth. In turn, aboveground and belowground herbivory can exert an effect on nutrient exchange between plants and their associated microbes, primarily on the key resources such as carbon (C), nitrogen (N) and phosphorus (P). Furthermore, it shows that herbivory, in the presence of plant associated beneficial microbes, has no negative effect on plant N and C content. The molecular mechanisms underlying these ecological interactions are being systematically uncovered. In order to outline the research progress in this field, this review synthesizes the current scientific literature regarding the mutual effect of nutrients on plant–herbivore interactions. It aims to support efforts in maintaining the sustainability of ecosystem by optimizing plant defense strategies via managing nutrient variability.