Respiration Rate, Mitochondrial Activity and Mitochondrial Structure in the Cotyledons of Phaseolus vulgaris L. during Germination

Parallel observations have been made on changes in respirationrate, mitochondrial activity, and the fine structure of mitochondria,in the cotyledons of Phaseolus vulgaris germinating at 25^? Cin the dark. While oxygen uptake of the intact cotyledons risesto a peak between the third and fifth days of germination, mitochondrialactivity falls from 36 hours onwards. In most of the storagecells, mitochondrial cristae have become swollen and the matrixhas darkened by the third day. The continulng rise in respirationrate beyond 36 hours could be accounted for by the increasein soluble oxidative activity, which occurs while mitochondrialactivity is falling. Alternatively, it could be mediated bymitochondria from the vascular bundle cells, where swellingand darkening are delayed till after the fifth day of germination,and where there is proliferation of cristae till the fourthday.