Effect of NaCl and PEG Iso-osmotic Stresses on Photosynthetic Characteristics and Sucrose Metabolizing in Tomato Leaf

In order to compare and analyse the reasons of salt stress and water stress influence tomato yield and fruit quality from the perspective of carbohydrate production and metabolism,the tomato variety Liaoyuanduoli was used,the same osmotic potential of NaCl and PEG6000 was used to simulate salt stress and water stress,photosynthetic characteristics and sugar metabolism in tomato leaves of two treatment was studied.The results showed that:Iso-osmotic NaCl and PEG stresses cause reduced net photosynthetic rate of tomato leaf,within 14 d PEGl treatment reduced more than NaCl treatment,after 14 d NaCl treatment reduced more than PEG treatment,but,overall,little difference between the two treatment;Iso-osmotic NaCl and PEG stresses reduced stomata conductance,intercellular CO2 concentration and transpiration rate in tomato leaves,increased stomata limitation value;Iso-osmotic NaCl and PEG stresses reduced chlorophyll a,b and total chlorophyll content,decreased chlorophyll a/b in tomato leaves,little difference between two treatments.Under iso-osmotic NaCl and PEG stresses,the content of fructose and glucose increased significantly in tomato leaves compared with control,PEG stress increased more than salt stress,sucrose and starch content reduced in tomato leaves compared with control,water stress reduced more than salt stress;Iso-osmotic NaCl and PEG stresses increased activity of sucrose invertase in tomato leaves,PEG stress increased more than NaCl stress.The results show that:NaCl and PEG stress both destroyed tomato leaf photosynthetic function,decreased the efficiency of photosynthesis,but little difference between two treatments;NaCl and PEG stresses altered the direction of sucrose metabolism in tomato leaves,increased significant the decomposition of starch and sugar,increased the content of fructose and glucose,the impact of PEG stress on sucrose metabolism was significantly greater than NaCl stress in tomato leaves.