Bull. Spec. CORESTA Congress, Yokohama, 1996, p. 127, A20

Comparison effects of topping of fertile and sterile tobaccos

BERBEC S.
Institute of Field Crop Production, Lublin, Poland.
In a three-year pot experiment the effects of topping were compared for two forms of Virginia tobacco: fertile (forming seeds) and sterile (seedless). The aim of the experiment was to verify (or confirm) the opinion, that the positive effect of topping is achieved by preventing plants forming seeds. Plants were topped at the stage of first flower to a height of 16 leaves. After topping, suckers were removed on successive occasions. The topping brought about the same morphological changes in both forms: significant increase of root development (by 68% in the fertile plants and 48% in the sterile), thicker stem, larger and thicker leaves, lower share of midrib in lamina. In both forms of tobacco the topping positively influenced the chemical composition of the leaves: significantly increasing nicotine content, markedly increasing carbohydrates, while protein and ash slightly decreased. In general, the measured changes were deeper in the fertile tobacco, but the tendency in all features were the same every year. It means that the promotion of root growth caused by topping is the chief (if not only) factor of changes in plants morphology and in the chemical composition of the leaves.