Nitrogen supply after removing the shoot apex increases the nicotine concentration and nitrogen content of tobacco plants
2005
Xi, X.Y. | Li, C.J. | Zhang, F.S.
BACKGROUND AND AIMS: High nicotine concentrations in leaves, especially in the upper leaves, offer a serious problem for the cultivation of tobacco (Nicotiana tabacum). Preliminary field experiments showed that rapid mineralization of soil N during late stages of growth may contribute to high nicotine concentrations in leaves. METHODS: A sand-culture experiment was carried out in the greenhouse. The N supply was controlled during the experiment, and different amounts of ¹⁵N were supplied during late stages of growth (after removal of the shoot apex), to investigate the contribution of the N taken up at this time to the N content of and nicotine concentration in tobacco plants. KEY RESULTS: Addition of 1.6 g or 4 g ¹⁵N-labelled NH₄NO₃ after removing the shoot apex and flushing out the ¹⁴N did not increase leaf dry weights; however, it did result in delayed leaf senescence, more lateral bud formation, and an increase in ¹⁵N as a proportion of total N, and nicotine-¹⁵N as a proportion of total nicotine-N in each organ. The nicotine concentration, ¹⁵N and nicotine-¹⁵N abundances were increased from the bottom to the top leaves. When more ¹⁵N-labelled NH₄NO₃ was supplied, the nicotine concentration in leaves increased, and so did the ¹⁵N abundance in nicotine-N. CONCLUSION: Enhanced N supply in the later growth stages (after removing the apex) increased N content and nicotine concentration in tobacco plants. Nicotine was synthesized de novo during the late growth stages.
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