Changes in ultrastructure of mitochondria during the cell cycle.

The structure of mitochondria in the antheridial filaments of Chara varies. At the same stage of interphase, there are half condensed mitochondria having a very dense matrix (type A) slightly swollen mitochondria with very light matrix (type D) and, most frequently, the "orthodox" mitochondria (types B and C). The heterogeneous structure of the mitochondria disappears 20 minutes after administering 2-deoxyglucose, i. e., when influenced by an elevated level of cellular ADP. During the course of the cell cycle the ratio between mitochondria A, B, C and D changes several times. These changes suggest that possible reversible conversion of one type of mitochondrion into another and this probably results from changes in the functional status of the mitochondria during different phases of the cell cycle.