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Exogenous jasmonic acid mimics herbivore‐induced systemic increase in cell wall bound peroxidase activity and reduction in leaf expansion
Author(s) -
Moore Jason P.,
Paul Nigel D.,
Whittaker John B.,
Taylor Jane E.
Publication year - 2003
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1046/j.1365-2435.2003.00767.x
Subject(s) - biology , jasmonic acid , peroxidase , herbivore , botany , cell wall , point of delivery , biochemistry , enzyme , salicylic acid
Summary1 Jasmonic acid (JA), a ubiquitous regulator of the wound response in plants, is part of a long distance defence signalling pathway and when applied exogenously induces several defence related responses in many species including the activation of proteinase inhibitor (PIN) proteins and defence‐related metabolites. 2 There is evidence for an induced systemic resistance mechanism linking increased cell wall peroxidase activity with reductions in leaf expansion rates in Rumex obtusifolius , following limited grazing by the chrysomelid beetle Gastrophysa viridula . We hypothesised that herbivory induces strengthening of cell walls in distal, non‐damaged tissue through increases in peroxidase activity and that this mechanism was mediated systemically by JA. 3 JA was applied to the fully expanded fourth leaf of R . obtusifolius and expansion of leaf 8 was measured over 19 days. Treatment with exogenous JA induced a temporary reduction in the expansion rate of leaf 8 beginning 6 days after treatment. This reduction continued until day 7 and reduced final leaf areas in treated plants by approximately 20%. 4 Final epidermal cell areas in leaf 8 were reduced by approximately 25%, while epidermal cell numbers remained unchanged. 5 Cell wall bound peroxidase activity was measured in leaf 8 over a 6‐day period following application of JA to leaf 4. Activity increased approximately 9‐fold 2 days after treatment, before returning to control activities on day 3. 6 Treatment of leaf 4 with JA reduced the gregariousness of G . viridula larvae on the fully expanded leaf 8. 7 We postulate that JA acts as a signalling molecule in a long‐distance pathway responsible for inducing resistance to future attack through increases in cell wall bound peroxidase activity leading to cell wall toughening, while incurring a potential ecological cost in the form of reductions in subsequent leaf expansion.