Abstract: Flue-cured tobacco cv.K326 and V2 were sprayed on the foliage separately with plant growth regulators,2,4-D and 6-BA,at the concentration of 0,0.1,0.3,1.0,5.0 mg/mL respectively when the 3rd and 7th leaves grew in floating system,and the low epidermis was sampled once the 9th leaf appeared.The results showed that the stoma in low epidermis was obviously affected by plant growth regulators;with the increase of concentration of plant growth regulator,the density of stoma gradually declined,it approached the minimum when regulator concentration was 0.3 mg/mL,and increased subsequently;the proportion of shapeless stomas raised while the opening of stoma decreased gradually.When the concentration was >0.1 mg/mL,the lengthening and widening of stoma were inhibited.The number of chloroplast in each pair of guard cells of cv.K326 upped to the top when the concentration of the regulators were 1.0 mg/mL,and that of cv.V2 upped to the top when the concentration of 6-BA was 0.3 mg/mL or that of 2,4-D was 1.0 mg/mL.