Kapulnik, Y., Institute of Field and Garden Crops, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Yalpani, N., AgBiotech Center, Cook College, Rutgers University, P.O. Box 231, New Brunswick, NJ 08903-0231, United States
Raskin, I., AgBiotech Center, Cook College, Rutgers University, P.O. Box 231, New Brunswick, NJ 08903-0231, United States

Cyanide-resistant, alternative respiration in Nicotiana tabacum L. cv Xanthi-nc was analyzed in liquid suspension cultures using O2 uptake and calorimetric measurements. In young cultures (4-8 d after transfer), cyanide inhibited O2 uptake by up to 40% as compared to controls. Application of 20 μM salicylic acid (SA) to young cells increased cyanide-resistant O2 uptake within 2 h. Development of KCN resistance did not affect total O2 uptake, but was accompanied by a 60% increase in the rate of heat evolution from cells as measured by calorimetry. This stimulation of heat evolution by SA was not significantly affected by 1 mM cyanide, but was reduced by 10 mM salicylhydroxamic acid (SHAM), an inhibitor of cyanide-resistant respiration. Treatment of SA-induced or uninduced cells with a combination of cyanide and SHAM blocked most of the O2 consumption and heat evolution. Fifty percent of the applied SA was taken up within 10 min, with most of the intracellular SA metabolized in 2 h. 2,6-Dihydroxybenzoic and 4-hydroxybenzoic acids also induced cyanide-resistant respiration. These data indicate that in tobacco cell-suspension culture, SA induces the activity and the capacity of cyanide-resistant respiration without affecting the capacity of the cytochrome c respiration pathway.