Studies on respiration in developing poppy seeds

Abstract

The excised ovules of Papaver somniferum have been used to investigate the endogenous uptake of oxygen during their maturation into seeds. Effect of some activators and inhibitors and the activity of succinic dehydrogenase have been studied. There appears to be an intimate correlation between respiration and the anatomical changes in the ovule. There is an increased oxygen uptake during or immediately preceding the events of (a) pollination, (b) divisions of the endosperm nuclei, (c) cell wall formation in the endosperm, and (d) elongation of cotyledons. The activity of succinic dehydrogenase follows a curve essentially similar to that of oxygen uptake. The low intensity of respiration during certain period of development appears not to be due to exhaustion of endogenous substrates. Endogenous substrates do, however, appear to be limiting on the days when maximum respiration occurs since added sugar does significantly enhance oxygen uptake. The results with two inhibitors, iodoacetate and fluoroacetate, suggest the operation of glycolysis and tricarboxylic acid cycle during the earlier phase of seed development when the rate of growth is highest.