|Field, Taylor - PLANT BIOLOGY UOFI URBANA|
|Nedbal, Ladislav - PLANT BIOLOGY UOFI URBANA|
Submitted to: Plant Physiology and Biochemistry
Publication Type: Abstract Only
Publication Acceptance Date: August 25, 2000
Publication Date: N/A
Technical Abstract: We investigated the relationship between nonphotochemical plastoquinone reduction and chlororespiration in leaves of growth chamber grown sunflower. Following a short induction period, leaves of previously illuminated sunflower showed a substantially increased level of minimal fluorescence following a light to dark transition. This increase in minimal fluorescence was reversed by far red illumination, inhibited by rotenone or photooxidative methylviologen-treatment and stimulated by fumigation with carbon monoxide. Employing flash-induced electrochromic absorption change measurements, we observed that the capacity of sunflower to perform plastoquinone reduction in the dark influenced the activation state of the chloroplast ATP synthase although chlororespiratory uH+ formation alone does not fully explain our observations. We have added several important new observations to the work of others forming the first strong experimental evidence that chlororespiratory, nonphotochemical plastoquinone reduction and plastoquinol oxidation occur in the chloroplasts of higher plants. We have introduced procedures for monitoring and manipulating chlororespiratory activity in leaves that will be important in subsequent work aimed at defining the pathway and function of this dark electron flux in higher plant chloroplasts.