Laser Activation of Rapid Absorption Changes in Spinach Chloroplasts and Chlorella

Abstract

The kinetics of the520 mu absorption change in spinach chloroplasts and Chlorella vulgaris following a flash from the ruby laser have been determined as follows: rise halftime [less than or equal to] 0.3 x 10-6 sec; rapid recovery halftime = 5 to 6 x 10-6 sec: ; intermediate recovery halftime = 4x 10-4 sec. (spinach chloroplasts only); slow recovery halftime = 12 to 170 x 10-3 sec, dependent on the measuring light intensity and aerobicity of the suspension. The rapid phase of the 520 mu reaction is approximately independent of temperature, from 295[degree] to 77[degree] Absolute. With increasing oxygenation of thesample, the extent of the rapid phase decreases, the extent of the slow phase increases, while the extent of the intermediate phase in spinach chloroplasts remains constant. In spinach chloroplasts, no recovery halftime of the 3 recovery phases for the 520 mu absoprtion change was observed to correspond to the halftime for oxidation of cytochrome f 1/2 = 1-3 x 10-3 second).