EFFECT OF Cd,Pb STRESS ON SCARENGING SYSTEM OF ACTIVATED OXYGEN IN LEAVES OF TOBACCO Overexpression of Sweet Pepper Glycerol-3-Phosphate Acyltransferase Gene Enhanced Thermotolerance of Photosynthetic Apparatus in Transgenic Tobacco Isolation and Expression Pattern Analysis of Two Ferritin Genes in Tobacco INFLUNENCE OF CHLORINE AND POTASSIUM ON YIELD AND QUALITY OF FLUE-CURED TOBACCO