Effects of nitrogen fertilization on carbohydrate content and
related metabolic enzymes of flue-cured tobacco in paddy field and highland

Nitrogen is one of the most important elements for tobacco growth and development. In order to reveal effects of nitrogen fertilization on soluble carbohydrate, sucrose, fructose, sucrose-phosphate synthase（SPS）and sucrose synthase（SS）of tobacoo leaves at rosette, rapid growth, and lower, middle and upper stalk position harvesting stages, and on total soluble carbohydrate, total nitrogen, and nicotine concentrations of flue-cured leaves in paddy field and highland conditions, field experiments were conducted with split design which two nitrogen sources, nitrate and ammonium nitrogen, are severed as main plot and five nitrogen levels are severed as split plot. Results show that concentrations of soluble carbohydrate, sucrose, and fructose of tobacco leaves are increased significantly when nitrate and ammonium nitrogen are applied into paddy field and highland from 0 to120 and 0 to 112.5 kg/ha, respectively. The impact of nitrate and ammonium nitrogen applications on tobacco carbohydrate accumulation is not markedly different in both lands, while carbohydrate concentration of tobacco leaves in paddy field is higher than that in dry land. Moreover, SS and SPS activities are also increased when nitrogen fertilizer applied. Total soluble carbohydrate (305342 mg/g, DW). Furthermore, carbohydrate concentration under ammonium applications in both lands (averagely, 366.5 and 331.3 mg/g, DW) is much higher than that under nitrate applications (averagely, 358.9 and 317.2 mg/g, DW). However, leaf total nitrogen and nicotine (1216 mg/g, DW) in highland are much lower than those in paddy filed (1620 mg/g, DW), which would result in the unbalance between soluble carbohydrate concentration and nitrogen containing compounds.