Effects of interplant defence signalling on production and allocation of biomass :

Abstract: Barley plants are known to release volatiles, both when infested by aphids and uninfested. Neighbouring barley plants have in previous studies been seen to induce a defence mechanism against aphids when exposed to these volatiles. In this study investigated whether volatiles from aphid infested barely plants as well as two chemicals, methyl jasmonate and methyl salicylate, affect biomass allocation and growth of exposed plants. In order to accomplish this, a first experiment was done in which barley cultivars Alva and Kara were infested by aphids. Other, uninfested, Kara plants were exposed to air from the aphid-infested plants. Plant samples were taken at five occasions and growth parameters were calculated. No changes in total dry weight were seen between the treatments and control plants and no changes in biomass allocation appeared. A second experiment was conducted, in which Kara plants were exposed to volatiles from methyl salicylate and methyl jasmonate. These two chemicals are thought to be involved in volatile communication between plants and have been shown to induce defence against aphids in barley plants. No change in total dry weight or biomass allocation was found after exposure to the chemicals. The results suggest that the induced defence in barley plants exposed to aphid infested barley plants, methyl salicylate or methyl jasmonate does not correlate with green plant biomass costs.