|Field, Taylor - PLANT BIO UOFI URB IL|
|Cheeseman, John - PLANT BIO UOFI URB IL|
Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: April 28, 1996
Publication Date: N/A
Technical Abstract: Photosynthetic electron transport at steady-state has been shown often to be defined strictly in terms of RuBP use and regeneration in C3 plants. However, R. Mangle leaves were previously shown to sustain an electron flux not balanced with the demands calculated for rubisco-dependent CO2 and O2 assimilation rates. To explore the chloroplast level processes responsible for the mismatched electron transport rate, we utilize an approach that combined chlorophyll fluorescence and infrared gas exchange analysis on leaves to estimate whole-chain electron transport rate and carbon reduction cycle flux, respectively. An inhibitor of rubisco was employed to stop linear electron product allocation to RuBP use. We found a persistent residual electron transport rate, around 50 umol m**-2 s**-1 electrons**-1 that was 30 percent of the uninhibited electron transport rate, when rubisco activity was inhibited with glyceraldehyde. Varying O2 concentration to diminish molecular oxygen as an electron sink led to a large decline in the residual electron flow. Our result implicate the importance of excess electron flow shunted to molecular O2 when rates of excitation and linear electron transport are beyond the abilities of energy dissipation through nonphotochemical quenching, CO2 assimilation, and photoespiration. This research was supported by DOE Interdisciplinary Training Grant for Photosynthesis Research Training Grant 92ER20095.