Induced chemical defence is a cost-efficient protective strategy, whereby plants induce the biosynthesis
of defence-related compounds only in the case of pest attack. Plant responses that are pathogen specific
lower the cost of defence, compared to constitutive defence. As nitrogen availability (N)in the root zone is
one ofthe levers mediating the concentration of defence-related compounds in plants, we investigated its
influence on response traits oftomato to two pathogenic bacteria, growing plants hydroponically atlow or
high N supply. Using two sets of plants for each level of N supply, we inoculated one leaf of one set of plants
with Pseudomonas syringae, and inoculated the stem of other set of plants with Pseudomonas corrugata.
Tomato response traits (growth, metabolites) were investigated one and twelve days after inoculation. In
infected areas, P. syringae decreased carbohydrate concentrations whereas they were increased by P. corrugata.
P. syringae mediated a redistribution of carbon within the phenylpropanoid pathway, regardless
of N supply: phenolamides, especially caffeoylputrescine, were stimulated, impairing defence-related
compounds such as chlorogenic acid. Inoculation of P. syringae produced strong and sustainable systemic
responses. By contrast, inoculation of P. corrugata induced local and transient responses. The effects of
pathogens on plant growth and leaf gas exchanges appeared to be independant of N supply. This work
shows that the same genus of plant pathogens with different infection strategies can mediate contrasted
plant responses.