RESPIRATORY OXIDATION BY MITOCHONDRIA FROM TOMATOES AT DIFFERENT STAGES OF RIPENESS

A number of factors in the isolation of good quality mitochondria from tomato fruit wall tissue have been critically examined. Particles from tomatoes at a number of stages during maturation and senescence were isolated and their ability to oxidise succinate, malate and α-ketoglutarate tested. In general, oxidation rates of the mitochondria and their respiratory control and ADP to oxygen uptake ratios reached a maximum with incipient ripeness and then declined with the onset of senescence. Thiamine pyrophosphate increased the oxidation rate of malate and α-ketoglutarate at all stages and appeared to prevent instances of inhibition probably due to the accumulation of oxaloacetate. Particles from the green side of 'blotchy' fruit had characteristics similar to those from normal fruit at the mature green stage, while the red side yielded particles that were similar to those from evenly coloured overripe fruit. Fruit having the dominant allele 'Never ripe', which causes extreme slowness in ripening, appeared to have mitochondria comparable in behaviour with those isolated from fruit undergoing normal maturation and senescense. © 1969 Dr. W. Junk N. V.