Biochemical and Structural Changes in Mitochondria and Other Cellular Components of Pea Cotyledons During Germination

Abstract

Integrated studies comprising biochemical and electron microscopic analysis suggested that the increase in respiratory activity of pea cotyledon mitochondria during germination results from further development of the original mitochondria present in dormant seeds. Electron microscopy of isolated mitochondria as well as mitochondria in situ has revealed that membranes are scarce in the mitochondria present in dormant seeds. Mitochondrial cristae become well developed during the initial stages of germination. Crude mitochondrial preparations from pea cotyledons were fractionated by sucrose density gradient centrifugation and analyzed through electron microscopy. These studies showed that, at all stages of germination, "peroxisome"-like structures were present in the fractions of higher sucrose densities than that containing mitochondria. Biochemical studies revealed that the activities of catalase (H 2 O 2 :H 2 O 2 oxidoreductase, EC 1.11.1.6) and peroxidase (guaicol:H 2 O 2 oxidoreductase, EC 1.11.1.7) were associated mainly with these fractions and their activities increased during germination.