Inhibition of foliar gas exchange by ethylene is an ultrasensitive response. [Glycine max]
- Oak Ridge National Lab., TN (USA)
The inhibition of foliar gas exchange as a function of ethylene (C{sub 2}H{sub 4}) concentration was examined to evaluate the potential role of C{sub 2}H{sub 4} in mediating gas exchange responses to environmental stress. Net photosynthesis (P{sub N}) and stomatal conductance to H{sub 2}O vapor (g{sub t}) were measured in soybean (Glycine max) seedlings after a 4 h exposure to C{sub 2}H{sub 4} (0-20 {mu}l {Gamma}) in a controlled environment system. Continuous steady-state measurements of leaflets held at a constant angle to incident light confirmed the magnitude of the maximal response and the time course of response. The declines in gas exchange showed saturation, with half-maximal response at 0.15 {mu}l {Gamma}{sup 1} for g{sub s} and 0.35 {mu}l {Gamma}{sup 1} for P{sub N}. Concentration-response curves for both functions were similar to those reported for C{sub 2}H{sub 4} binding (in vivo and in vitro) and for hormonally mediated C{sub 2}H{sub 4} actions. Kinetic analyses of the saturation patterns using the Hill equation showed both responses to be ultrasensitive, i.e., provide a relatively large change in gas exchange for a small change in C{sub 2}H{sub 4} concentration. The patterns of inhibition of g{sub s} and P{sub N} and the ultrasensitivity of both responses suggest a role for endogenously produced stress C{sub 2}H{sub 4} in mediating the responsiveness of foliar gas exchange to many environmental stresses.
- OSTI ID:
- 6937832
- Journal Information:
- Plant Physiology, Supplement; (USA), Vol. 89:4; ISSN 0079-2241
- Country of Publication:
- United States
- Language:
- English
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