Effects of Aging and Temperature on Respiratory Metabolism of Green Leaves

Abstract

Pea plants were grown at 10, 20 (optimum) and 30[degree] and leaves were taken at various developmental stages to determine the effects of aging and growing temperature on their respiratory capacity. QO2''s of intact leaves decreased 40-60% and 50-60% with increasing age and temperature respectively, and conversion of acetate-1-C14 to C14o2 showed the same pattern. Oxidation of 7 Krebs cycle intermediates by mitochondrial preparations decreased 60-100% and 30-100% with increasing age and temperature respectively, and P/O ratios close to theoretical were obtained only with mitochondria from young leaves at all growing temperatures. With aging, several electron transport enzyme activities decreased 50-60%, and electron micrographs of leaf sections showed structural disorganization of mitochondria. The results show decreasing respiratory and mitochondrial activities as well as increased disorganization of mitochondrial structure with aging. The only effect of exposure to suboptimal or supraoptimal growing temperatures is that of either decelerating or accelerating the normal demise of the respiratory system.