菸草植株下部叶片未到正常成熟期而提前發黃甚至枯死的現象,称为底烘。發生底烘的叶片,單位面积的干重大大降低,叶中养分含量也大为减少。据中国农業科学院菸草研究所一九五九年测定結果:每二十片叶烤后干重,正常成熟叶为九点五克,而底烘叶仅五点三克,干重减少了百分之四十四点二且成焦片。我們曾初步測定叶片中糖分的含 Lower leaves of tobacco plants did not reach the normal maturity and yellowing or even dead before the phenomenon, known as the end of bake. Occurred at the end of baking leaves, dry weight per unit area greatly reduced the leaf nutrient content is also greatly reduced. According to the results of a survey conducted by the Institute of Tobacco Research, Chinese Academy of Agricultural Sciences in 1959, the dry weight per twentieth leaves after roasting was about 9.5 g for normal mature leaves and only 5.3 g for the bottom leaves, reducing the dry weight by 100% Fourteen forty-two and into the coke. We have initially determined the content of sugar in leaves