RESPIRATION OF MICROSPORES DURING INDUCTION OF POLLEN EMBRYOGENESIS IN TOBACCO

Contribution of cytochrome-mediated respiration, alternative (cyanide-resistant) respiration, and residual respiration to the total respiration of microspores of tobacco (Nicotiana tabacum L.) was measured during induction of pollen embryogenesis. Embryogenesis was induced by incubation of excised flower buds or isolated microspores at a cold temperature (7 days at 8-degrees-C). In all cases, the cytochrome-mediated respiration was predominant. Cooling the flower buds resulted in activation of the alternative pathway, whereas cooling the suspension cultures stimulated the residual respiration. There was a positive correlation between the frequency of pollen embryogenesis in suspension cultures and the residual respiration fraction (r = 0.8). The relationship between the oxidative metabolism and the pollen embryogenesis is thus demonstrated, and the effect of sporophyte tissues on the respiration pattern during induction of embryogenesis is shown. The revealed activation of the residual respiration in isolated microspores is presumably attributed to nonmitochondrial oxidases.