Study On Regulating Tomato Quality By Deficit Irrigation Under Closed Cultivation Mode

Deficit irrigation is a water-saving measure in water-scarce Chinese agriculture.Using tomatoes,we investigated the effects of different degrees of deficit irrigation on tomato growth,yield and quality,and the changes in physiological indicators of different tomato varieties at different times,days and types after deficit irrigation.The aim was to show the relationships between the relevant physiological indicators and to provide a theoretical basis for scientific irrigation of tomato grown on inorganic substrates with nutrient recycling.The main research findings are as follows.（1）With the increase of deficit degree,plant growth and photosynthesis were inhibited,and tomato yield and light energy conversion efficiency decreased.The water use efficiency of leaves was improved,and the fruit quality and antioxidant enzyme activity increased first and then decreased.The fruit quality was the best under T2treatment of 0.8 L·plant^-1·d^-1,and the leaf structure and antioxidant enzyme activity were the highest under T3 treatment of 1.1 L·plant^-1·d^-1 and T4 treatment of 1.3 L·plant^-1·d^-1.It indicated that moderate deficit irrigation could improve fruit quality,leaf structure and antioxidant enzyme activity,but the quality and leaf related indexes decreased beyond a certain range.（2）After deficit irrigation treatment,the fruit quality of tomato was improved under different ripening stages and different deficit days.Under the deficit irrigation of 1.0L·plant^-1·d^-1 in T2 treatment,the fruit quality of tomato at different maturity stages and different deficit days was better,and the weight and yield of single fruit were the lowest.The fructose content in T2 treatment was significantly higher than that in control group by 25.22%,16.20%,13.67%,17.00%;The citric acid content was significantly higher than that of the control group by 7.84%,36.45%,35.64%and 54.19%.The activities of enzymes related to glucose metabolism changed and invertase increased,among which the activities of sucrose synthase（decomposition direction）increased by 38.95%,59.17%,25.53%and 29.79%respectively.At the same time,the activities of antioxidant enzymes,the contents of proline and malondialdehyde increased in different days of treatment.At the same time,with the increase of deficit degree,the microstructure,stomatal structure and chloroplast ultrastructure of leaves were affected to some extent,and the related structures of leaves were damaged to some extent.（3）Deficit irrigation inhibited the plant height,stem diameter,leaf number and photosynthetic parameters of’YS12’common internode and’YS06’short internode tomato varieties,increased the nutrients and flavor substances in tomato fruits,and decreased the yield per plant.The higher the deficit degree,the greater the decline.Different types of tomato had the highest quality under 1.0 L·plant^-1·d^-1 deficit irrigation under T2 treatment.At the same time,the growth of short internode tomato was less inhibited and the drought tolerance was strong after deficit irrigation,and the quality improvement effect of common internode tomato was more significant.In summary,moderate deficit irrigation can improve tomato fruit quality and flavour,but may also be associated with some degree of yield loss and tomato leaf damage.In summary,moderate deficit irrigation can improve tomato fruit quality and flavour,but may also be associated with some degree of yield loss and tomato leaf damage.