Effects of Nitrogen Application Rates on Tissue Structure and Cell Development of Flue-cured Tobacco Leaves

The tissue structure and cell development of flue-cured tobacco leaves were studied in field at different levels of nitrogen fertilizer application with paraffin method and electron microscopic chemical method. The results showed that:1)nitrogen deficiency would hinder the elongation of palisade cells and expansion of lacunae, which resulted in a higher palisade cell density and smaller ratios of palisade tissue thickness to spongy tissue thickness as well as to leaf thickness, the leaf developed slowly, its tissue became thinner;2)nitrogen had a function of promoting the development of chlorophyll, where a large amount of starch grains and osmiophilic globules accumulated. However, over-supplying of nitrogen would delay and extend the development of leaf cells. As a result, at later growth stage, the accumulation of photosynthesis products remained at a higher level, which was not beneficial to the degradation of chlorophyll inclusions in leaf cell, persistent-green postponed the mature of leaf and deteriorated leaf quality.