STUDIES ON RESPIRATION IN DEVELOPING POPPY SEEDS

The excised ovules of Papaver somniferum have been used to investigatethe endogenous uptake of oxygen during their maturation intoseeds. Effect of some activators and inhibitors and the activityof succinic dehydrogenase have been studied. There appears tobe an intimate correlation between respiration and the anatomicalchanges in the ovule. There is an increased oxygen uptake duringor immediately preceding the events of (a) pollination, (b)divisions of the endosperm nuclei, (c) cell wall formation inthe endosperm, and (d) elongation of cotyledons. The activityof succinic dehydrogenase follows a curve essentially similarto that of oxygen uptake. The low intensity of respiration duringcertain period of development appears not to be due to exhaustionof endogenous substrates. Endogenous substrates do, however,appear to be limiting on the days when maximum respiration occurssince added sugar does significantly enhance oxygen uptake.The results with two inhibitors, iodoacetate and fluoroacetate,suggest the operation of glycolysis and tricarboxylic acid cycleduring the earlier phase of seed development when the rate ofgrowth is highest. (Received September 1, 1964; )