Action of ozone on foliar gas exchange in Glycine max L. Merr: a potential role for endogenous stress ethylene

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Abstract
SUMMARY: A rapid surge in the foliar production of ethylene (C2H4), a growth regulator, is a well documented phenomenon in plants experiencing a variety of environmental stresses. The physiological significance of this stress‐induced C2H4 is not resolved. Because exogenous C2H4 can induce changes in foliar gas exchange in a variety of plant species, we tested the hypothesis that the endogenous production of stress C2H4 due to the representative environmental stress of ozone (O3) is linked to observed changes in stomatal conductance to water vapour (gsH2o) and carbon dioxide assimilation (A) in Glycine max (L.) Merr. This objective was accomplished using seedlings in hydroponic culture which were administered aminoethoxyvinylglycine (AVG), a metabolic inhibitor of stress C2 H4 synthesis, and subsequently challenged with O3. The responsiveness to O3 stress of gsH2O and A was either substantially diminished (A) or eliminated GS, H2O) when stress C2H4, production in the leaf interior was metabolically inhibited by AVG. These data support the hypothesis that the rapid surge in production of stress CJJH, in response to chronic‐level stresses in general and O3 specifically is not simply an indicator of the plant's physiological activity but rather is a chemical messenger or trigger that subsequently mediates some of the notable changes in carbon gain, stomatal physiology, and water use.