Chloroplast and nitrate reductase activities were measured to ascertain the effects of alien cytoplasms on physiological processes in tobacco. Five sources of cytoplasm from related species were produced by transferring the Nicotiana tabacum L. ‘Hicks Broadleaf’ (Hicks) genome into the cytoplasms of N. bigelovii Torr., N. undulata Ruiz and Pavon, N. megalosiphon Heur. and Muell., N. suaveolens Lehm., and N. plumbaginifolia Viv. Normal Hicks (N. tabacum nucleus in N. tabacum cytoplasm) Served as the control. These comparisons provided an estimate of the degree of influence of the respective alien cytoplasmic environments on the expression of the N. tabacum genome with regard to the cellular processes investigated. Greenhouse-grown tobacco plants with cytoplasms derived from N. undulata, N. suaveolens, N. megalosiphon, and N. plumbaginifolia tended to be less efficient in reducing nitrate than control plants. With the exception of the N. bigelovii entry, Hill reaction activity in the alien cytoplasm entries tended to be lower than the control at leaf position 4 and higher at leaf position 6. A positive relationship between Hill reaction activity and in viva nitrate reductase activity was observed. Early field growth of plants containing N. megalosiphon, N. suaveolens, or N. plumbaginifolia cytoplasms was slower than the control. Plants with these cytoplasms showed recovery of subsequent growth and no significant differences in cured leaf yield. Statistical correlations between the metabolic studies and field-grown tobacco performance were not made. Nevertheless, we conclude that if our results can ultimately be extrapolated to field grown plants, the physiological performance we observed in the laboratory might explain, in part, cytoplasmic effects on quantitative traits reported in the literature and associated with tobacco cytoplasms derived from N. suaveolens, N. megalosiphon, and N. plumbaginifolia.

(Full article published with kind permission from "Tobacco International")