The effect of temperature on the fluorescence kinetics of spinach chloroplasts

摘要: Abstract 1. The fluorescence kinetics of spinach chloroplasts were studied over the temperature range +40° to −196°. At temperatures above −5°, ratio steady-state level ( F ∞ initial 0 was determined by intensity excitation light. independent and equal yield in presence dithionite reduced ). In 3-(3,4-dichlorophenyl)-1,1-dimethylurea, there a rapid rise level. - ) untreated dependent on pH with maxima at 6.1 7.2; pH. 2. biphasic kinetics, observed 20° reproducible provided remained dark for few min between excitations, but −5° kinetic curve replaced an exponential subsequent excitations. Illumination far-red light restored their state, then obtained second excitation. An action spectrum restoration showed peak 707 nm. rate response declined gradually below it completely inhibited −30°. 3. Over −40° −196° obtained, only first Subsequent excitations gave immediate decreasing temperature. 4. results are discussed terms sequential series carriers (E,Q,P) reducing side Photosystem II. Analysis curves indicated P/Q 6, 1 Q per 140 chlorophylls. E is present smaller extent than Q. quantum efficiency reduction II To explain responses, postulated that oxygen interacts 3 sites electron transport chain chloroplasts.