In order to study the effect of exogenous GR24 on the growth physiology of tomato seedlings under heavy met-al Pb stress,the tomato variety Shanghai Ruby 908 was used as the experimental material.The experiment was conducted in a plant physiological material culture room,with an average temperature of 28 ℃ and an average relative humidity of 70.85％.Tomato seedlings with consistent growth status and three leaves and one heart were transplanted into 1/2 Hoagland nutrient solution.The experiment included four treatments:CK(complete nutrient solution),GR24(complete nutrient solution+50 nmol·L-1 GR24),Pb(complete nutrient solution+200 mg·L-1Pb),and Pb+GR24(complete nutrient solution+200 mg·L-1+50 nmol·L-1 GR24).The results showed that the Pb stress of 200 mg·L-1 reduced the plant height,root length,and single leaf area of tomato seedlings by 21.03％,35.15％,and 27.27％,respectively.Compared with individual Pb stress treatment,applying exogenous GR24 can significantly increase the content of chlorophyll,carotenoids,soluble sugars,soluble proteins,and bioaccumulation in tomato seedling leaves;significantly increase the activity of antioxidant enzymes such as SOD,POD,CAT,and root activity;reduce the content of H2O2,O2-·,proline and MDA in leaf.There-fore,exogenous application of 50 nmol·L-1 GR24 can alleviate the toxic effect of Pb stress on the growth of tomato seed-lings.
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