The two-year pot-culture experiments for cultivars were Yunyan85 were conducted during 2004 and 2005. Each pot was filled with 20 kg air dried soil． The planting dates were May 20 and May 13 in 2004 and 2005 respectively. Shading-controlled experiments were conducted 7d after topping with shade-cloth to achieve three different irradiances of 100%, 50% and 20% of full sunlight in 2004 , five different irradiances of 100%，60%，40%, 20% and 10% of full sunlight in 2005. The shade environment was created by using white button fabric with 5 meters long and 3 meters wide，hung horizontally 3 meters above the bottom of the pots．In ording to insure shading treatment effective in the early morning and late afternoon，each sides of the tobacco canopy were also covered by the same fabric．
The results indicated that. The thickness, rate of palisade tissue and spongy tissue of tobacco leaves at the ripe stage reduced when light intensity decreased. Weaker light intensity decreased the weight and thickness per leaf, weight per unit leaf area, leaf density and sugar content of flue-cured tobacco leaves, and increased content of stem ratio, nicotine, total nitrogen, potassium, chlorine, lutein, carotenoid and aroma constituent .