Cells of Nicotiana tabacum L. suspension cultures were treated with the res
piratory inhibitor rotenone, which specifically inhibits complex I activity
of mitochondria. Rotenone retarded cell growth, as shown by decreases in f
resh weight, dry weight and cell numbers on a suspension-volume basis. Howe
ver, rates of the coupled respiration were higher in rotenone-treated compa
red to control cells when expressed on a fresh-weight basis. Rates of the r
otenone-insensitive respiration increased substantially on both a fresh-wei
ght and extractable-cellular-protein basis 24 h after rotenone treatment. A
TP/ADP ratios were not significantly different between control and rotenone
-treated cells. Our results indicated that cells of tobacco suspension cult
ures were able to maintain a slow rate of growth and adequate ATP/ADP ratio
s without the operation of complex I.