Competition mediates costs of jasmonate-induced defences, nitrogen acquisition and transgenerational plasticity in Nicotiana attenuata

1. Plants adjust their phenotype in response to environmental signals, but little is known about the interaction of plastic responses to simultaneously occurring environmental stresses. 2. To examine the costs of induced resistance on reproductive performance in plants subjected to other important environmental variables, resistance was elicited with a jasmonate treatment (MeJA) to one, both or neither of two Nicotiana attenuata plants growing competitively in either high- or low-N soils. Half the plants were subjected to leaf removal (LR). (KNO3)-N-15 was used to quantify differences in N acquisition and allocation. Transgenerational effects were measured with seed germination and seedling performance tests. 3. An induced plant competing with an uninduced plant produced significantly fewer seeds, acquired less N-15 and allocated less N-15 to seed production. Uninduced plants competing with induced plants realized a comparable fitness benefit. 4. The costs of induction were greater under high N. Plants grown under low N minimized costs by allocating significantly more N to seeds. LR decreased seed production independently of any other effect. Low N and LR both reduced germination rates. 5. The effects of MeJA on seed germination depended on competition and N supply. The differences in germination rates resulted in dramatic fitness differences among offspring. 6. N. attenuata plants appear to use N availability and their induced status to alter their current phenotype and their offspring's phenotype to adjust to environmental changes that occur predictably over time in their natural environment.