The cembratriene-diols were synthetized by Nicotiana tabacum with the emergence of primary leaves. By contrast, (Z)-abienol appeared only 55 days after germination. Of the two major diterpenes on N. tabacum leaf surface, (Z)-abienol and alpha and beta-cembratriene-diols, only the latter were synthetized in the young plant. The conventional cotyledon test was modified. The plants were fed with a solution of half-strength Knop to develop primary leaves carrying trichomes, the unique site of this type of synthesis. The varietal differences obtained in 20 days plants were compared with those observed in adult plants. A good correlation was obtained (r = 0.900). This laboratory technique can be easily utilised during breeding to isolate hybrids which have high alpha and beta-cembratriene-diols levels.