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Kinetics of inhibition of foliar gas exchange by exogenous ethylene: an ultrasensitive response *
Author(s) -
GUNDERSON CARLA A.,
TAYLOR GEORGE E.
Publication year - 1988
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1988.tb00291.x
Subject(s) - photosynthesis , ethylene , chemistry , stomatal conductance , kinetics , glycine , saturation (graph theory) , fight or flight response , conductance , biophysics , stereochemistry , analytical chemistry (journal) , botany , biochemistry , chromatography , biology , amino acid , catalysis , mathematics , combinatorics , gene , physics , quantum mechanics
summary The objective of this study was to examine the inhibition of foliar gas exchange as a function of ethylene (C 2 H 4 ) concentration in order to evaluate the potential role of stress C 2 H, in mediating changes in gas exchange in response to environmental stress. Net photosynthesis (P N ) and stomatal conductance to H 2 O vapour (g s H 2 o) were measured in soybean ( Glycine max (L.) Merr cv. Davis) seedings after a 4 h exposure to one of a range of exogenous C 2 H 4 concentration (0–20μII −1 )in a controlled environment system. Declines in both P s and g s H 2 O shifted from first‐order (liner decline) to zero‐order (saturation response) with increasing C 2 H 4 concentration. The response of g s H 2 O to C 2 H 4 , was more pronounced than the response of P s , with maximal declines for g s H 2 O of 32–48%, and half‐maximal response at 0.15μII −1 . Corresponding parameters for P N were 18–29%, inhibition and half‐maximal response at 0–35μII −1 . Both response curves were similar to those documented for C 2 H 4 , binding and for hormonally mediated C 2 H 4 actions. Kinetic analysis of the saturation patterns by the Hill equation showed both responses to be ultrasensitive, i.e. they provide a relatively large change in gas exchange for a small change in C 2 H 4 concentration. Based on this ultrasensitivity, we propose that endogenous stress C 2 H 4 mediates some of the responsiveness of gas exchange to environmental stresses of natural and anthropogenic origin.