Figure 2.

A and B, Determination of ATP-synthesis (plus H⁺ leak)-sustained respiration (defined as [BHAM plus BSA and GTP]-resistant respiration) in states 3 (A) and 4 (B). State 4 (B) was measured after ADP exhaustion. Mitochondria (mito) were incubated in a standard reaction medium containing 0.5% BSA, 1 mm GTP, and 2 mm ADP (for state 3), as described in Methods. Two millimolar BHAM, 0.17 mm ADP, and 1.5 mm KCN were added. The numbers on the traces refer to the O₂ consumption rates in nmol min⁻¹ mg⁻¹ protein. The respiration of green tomato mitochondria is shown as an example. C, ATP-synthesis (plus H⁺ leak)-sustained respiration ([BHAM plus BSA and GTP]-resistant respiration) in state (st.) 3 (▪), state 4 (•), and state 4 plus oligomycin (♦) in the four stages of tomato fruit ripeness (G, green; Y, yellow; O, orange; and R, red). Respiratory rates are in nmol O₂ min⁻¹ mg⁻¹ protein. The data are presented as the means ± sd of four independent experiments. The respiratory control values (RC) obtained from the average values for states-3 and -4 respiration at each stage of ripening also appear.