INCREASE IN THE CAPACITIES OF THE CYTOCHROME AND ALTERNATIVE RESPIRATORY PATHWAYS IN TOBACCO CELLS CAUSED BY 2,4-D AND KINETIN

Addition of 2,4-D (2.2-mu-M) to a 2,4-D dependent cell suspension culture of Nicotiana tabacum L. var. White Burley that was starved for 2,4-D for 5 days did not result in an increase in oxygen uptake before the start of cell division. Within 3 h after addition of 2,4-D an increase in the capacity of both the cytochrome and alternative respiratory pathways was observed. This indicates an increase in number or size of the mitochondria rather than a specific stimulation of one of the pathways. The increase was not mediated by ethylene and the alternative pathway did not become engaged. At a concentration supraoptimal for the induction of cell division, 2,4-D not only increased the capacities but it enhanced total oxygen uptake as well, albeit transient. After addition of kinetin no cell division occurred, but it induced an increase in the respiratory capacities after 17 h.