|Field, Taylor - PLANT BIOLOGY UOFI URBANA|
Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: September 1, 1997
Publication Date: N/A
Technical Abstract: A recent model for sustained photoprotective nonphotochemical quenching involving hydrolysis of ATP by CF that maintains DpH and violaxanthin de-epoxidation in darkness was tested in leaves of cotton. The induction and relaxation kinetics for qN under 2000mmol quanta m-2 s-1 were observed in cotton leaves at 30C and 10C. Relaxation of qN in darkness was rapid in leaves at 30C, suggesting that qE-quenching accounted for most of qN in leaves at 30C. At 10C, qN induction was slowed compared to leaves at 30 and a significant amount of qN persisted for 90 minutes in darkness. Fluorescence quenching in 10C treated cotton leaves was correlated with sustained absorbance changes at 535nm in darkness. Using the flash-induced electrochromic shift to probe changes in thylakoid ionic conductance, we investigated whether DpH and CF activity was present in darkness during the interval in which fluorescence quenching was sustained. The role for ATP hydrolysis and other processes that could generate at dark sustained DpH in leaves (chlororespiration) are discussed.