Figure 1.

Factors influencing variability of plant defenses. Plant defensive traits are affected by various endogenous and external factors. Endogenous factors comprise plant genotype and ontogeny of plants or plant parts. External factors can be categorized as abiotic or biotic. Important abiotic factors that can influence plant defenses are light exposure, temperature, soil salinity, as well as water and nutrient availability. Biotic factors that can have an effect on plant defense are interspecific interaction with Rhizobia (in the case of legumes), mycorrhizal and endophytic fungi, pathogens as well as the interaction with conspecifics or different plant species.