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| Effects of Potassium and Nitrogen Interaction on Carbon and Nitrogen Metabolism of Tomato Leaves，Fruit Yield and Quality |
| WANG Jun-wei1，2，HUANG Ke1，DONG Yue-xia3，LI Zhong-qiang4，JI Yue-na5，WU Qiu-yun1* |
| 1College of Horticulture，Hunan Agricultural University，Changsha 410128，Hunan，China；2Key Laboratory of Biology and Genetic Improvement of Horticultural Crops，Ministry of Agriculture and Rural Affairs,Beijing 100081，China；3Shanghai Flower Variety Test Site，Shanghai 200000,China；4Hunan Agricultural Radio and Television School，Changsha 410001，Hunan，China；5Hunan Academy of Forestry，Changsha 410004，Hunan，China |
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Abstract Under the condition of substrate cultivation in greenhouse，taking tomato‘A20’as test material，this experiment adopted response surface central composite design with 2 factors and 5 levels；and studied the effects of different N and K nutrient combination treatments on tomato single plant yield，fruit quality，carbon and nitrogen metabolite，and enzyme activities of tomato leaf blades．The results showed that with the increase of nitrogen nutrient（within the scope of 74-414 mg · L-1），carbon and nitrogen metabolite，and enzyme activities of tomato leaf blades showed the tendency of first rise then decrease．With the increase of potassium nutrition（within the scope of 101-525 mg · L-1），the sugar content and sucrose phosphate synthase（SPS），activities of acid invertase（AI）and neutral invertase（NI）in tomato leaf blades showed an increasing tendency．While，the nitrogen metabolites and activities of Sucrose synthetase （SS），Nitrate reductase（NR），Glutarmine synthetase（GS）and Glutaymate synthase（GOGAT）increased initially and then decreased．Through constructing quadratic regression equation between various index and nitrogin/potassium 2 factors，we found that nitrogen and potassium nutrient was the main factor affecting nitrogen and carbon metabolism in tomato leaf blades．The interaction of nitrogen and potassium had significant effect on free amino acid content and Glutamine synthetase（GS）activity in tomato leaves．The correlation analysis showed that there was a high correlation between tomato yield，fruit quality and carbon and nitrogen metabolism in leaves．Nitrogen and potassium nutrition worked together on the process of carbon and nitrogen metabolism in leaf blades，and then to affect tomato yield and quality．Therefore，in actual vegetable production，reasonable combined application of nitrogen and potassium nutrient could promote carbon and nitrogen metabolism，thus acheiving high yield and superior quality．After we comprehensively analyzed the experement result，we understand that when the nitrogen content in nutrient solution was 300-350 mg · L-1 and potassium nutrient was 370-520 mg · L-1，the carbon and nitrogen metabolism in tomato leaf blades was exuberant，and tomato yield and fruit quality could reach a higher level．
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Received: 24 September 2019
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