| Abstract
| - Experiments were conducted in tobacco (Nicotiana tabacum L.) to investigate the effect of sodiumbicarbonate (NaHCO3) on the conversion of nicotine to nornicotine, a secondary alkaloid that canform the tobacco-specific nitrosamine N-nitrosonornicotine (NNN). The results showed that, underoptimum conditions, NaHCO3 stimulated nicotine conversion in converter plants to the maximumlevel predetermined by the genetic background. The conversion level in NaHCO3-treated leaves was2−3 times higher than that in control leaves. For young seedlings the optimum concentration of sodiumbicarbonate was 0.8% aqueous solution, and for adult plants the optimum concentration was 1%.Lower concentrations resulted in partial stimulation, whereas higher concentration damaged leaf tissueand resulted in a lower conversion level. Studies with different temperatures (from 22 to 43 °C) showedthat 37 °C was optimal. This temperature allowed the least amount of time, 2−3 days for matureleaves and 4−6 days for green leaves, for the major converters to reach >95% of nicotine conversion.An examination of leaves from different growth stages and stalk positions showed that the amountof time needed for conversion was longer for young leaves and shorter for mature leaves. Treatmentof leaves with NaHCO3 affords a rapid and convenient means of identifying and removing nornicotineconverter plants during growth in the greenhouse or field. Keywords: Tobacco; nornicotine; nicotine; conversion; NaHCO3; demethylation
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