Some Factors Involved in Oxygen Evolution From Triturated Spinach Leaves

Abstract

Spinach leaves were ground for 2 min. in M/20 phosphate buffer of pH 6.9, using 5 ml. of buffer/gm. fresh wt of tissue. The triturate was filtered and centrifuged for 20 min. at 3,000 times gravity. The supernatant was the "suspension" used in the Warburg manometric apparatus with an atmosphere of purified nitrogen. Illumination was 2,000 ft.-candles. All expts. were done at 25 C. No particles in the suspension were in the visible range, indicating that the active material from the leaves was in colloidal soln. The chlorophyll was found to be firmly adsorbed or chemically combined with protein. One or more of the constituents of the material was enzymatic. The cell-free and chloroplast-free suspensions evolved more oxygen under identical conditions than did small pieces of intact leaves, ground leaf tissue, or whole chloroplasts. Doubling the amt. of quinone to 4 mg./ 2 ml. of suspension increased the rate of oxygen evolution by 35%, and quadrupling the concn. caused a 60% increase. An important observation was the apparent necessity of minute amts. of CO2 to cause oxygen evolution.