Herbivore‐specific elicitation of photosynthesis by mirid bug salivary secretions in the wild tobacco Nicotiana attenuata

Summary• Herbivory is thought to be detrimental to plant fitness and commonly results in a metabolic shift in the plant: photosynthetic processes are typically down‐regulated, while resource allocation to defenses is increased in herbivore‐attacked plants, resulting in fitness costs of induced plant responses. • Wild tobacco, Nicotiana attenuata , attacked by Tupiocoris notatus mirid bugs becomes resistant against more damaging herbivores through mirid‐induced direct and indirect defenses. However, mirid‐induced resistance and tissue loss do not result in a reduction of plant fitness. These findings suggest induced metabolic responses allowing the plant to compensate for the lost tissue and resources allocated to defenses. • While feeding by Manduca sexta larvae results in a strong down‐regulation of photosynthesis, we demonstrate a specific induction of elevated photosynthetic activity in N. attenuata leaves by elicitors in mirid salivary secretions. The elevated CO 2 assimilation rate is sufficient to compensate for the loss of photosynthetically active tissue and balances the net photosynthesis of infested leaves. • We discuss the observed increase in the plant’s primary metabolic activity as a mechanism that allows plants to alleviate negative fitness effects of mirid attack and mediates the vaccination effects that result in a net benefit in environments with multiple herbivores.