Effects Of Combined Application Of Iron,zinc And Selenium On Tomato Growth And Fruit Quality

Iron and zinc are essential trace elements for plant growth and development,and selenium is a beneficial element for plants.As cofactors of various enzymes,the three play an important role in regulating plant redox balance,photosynthesis and quality formation.There have been many studies on the effects of combined application of zinc,iron,zinc and selenium on plant growth and nutrient absorption and utilization.However,the effects of iron,zinc and selenium combined application on the growth and nutritional quality of vegetable crops have not been systematically reported.For this reason,this experiment uses ‘Provence’ tomatoes as the test material,and uses a combination of root basal application and foliar spray.Explore the effects of combined application of iron,zinc and selenium on tomato biomass,photosynthetic characteristics and fruit quality,etc.It aims to provide a scientific basis for regulating tomato growth and fruit quality based on iron,zinc and selenium combined application.The main results are as follows:1.Both single application and combined application of iron,zinc and selenium increased the net photosynthetic rate of leaves,and the final performance was a significant increase in single fruit weight and horizontal and vertical diameter.Compared with Zn（R）and Fe（L）combined application of zinc and iron,the chlorophyll content and net photosynthetic rate of leaves were significantly increased,but the quality of single fruit was reduced;Compared with Se（R）,selenium-zinc and selenium-iron combined application showed no significant difference in chlorophyll content,net photosynthetic rate and single fruit weight.It shows that the interaction of zinc and iron is beneficial to promote the photosynthesis of plants,and the base application of 0.1 g·L^-1 zinc fertilizer can increase the weight of single fruit more significantly.2.Exogenous iron,zinc and selenium have a significant effect on fruit active substances and antioxidant enzyme activities.Compared with the control,single application of iron,zinc,and selenium was treated with foliar spraying of 100 μmol·L^-1Fe and 50 μmol·L^-1Zn.The promotion effect is obvious,and the activities of total phenols,flavonoids,lycopene,vitamin C,POD and CAT in the fruit are significantly increased;Compared with Zn（R）,the combined treatment of zinc and iron significantly increased the active substances in the fruit,but there was no significant difference in the activities of SOD and CAT,but the activity of POD decreased;Compared with Se（R）,the combination of selenium and zinc has significantly improved active substances,and the activity of CAT is significantly improved,but the activities of SOD and POD are reduced.In summary,Zn（L）and Zn（R）+Fe（L）treatments have better antioxidant effects on tomato fruits.3.Compared with the control,the foliar spraying of Fe,Zn and basal application of Zn,Se have a significant promotion effect on the soluble sugar,titratable acid,free amino acid and other quality indicators in tomato fruits.On the basis of basal Zn fertilizer,spraying Fe fertilizer on leaves can improve the photosynthesis of leaves and significantly increase the soluble sugar,soluble protein,soluble pectin content and sugar-acid ratio in the fruit.On the basis of basal Se fertilizer,foliar spraying with Zn fertilizer significantly increased the soluble solids,soluble sugar,soluble protein content and sugar-acid ratio in the fruit;Spraying Fe fertilizer on the leaves made the fruits accumulate more soluble solids,soluble sugars,and titratable acids,but the free amino acid content was significantly reduced.In summary,the treatments with Zn（L）,Zn（R）+Fe（L）,Se（R）+Zn（L）significantly improved tomato fruit quality.4.Exogenous iron,zinc and selenium have varying degrees of influence on the activity of sucrose metabolizing enzymes and sugar content.Compared with the control,except for the basal application of Se fertilizer,the reducing sugar and sucrose content in tomato fruits of all treatments increased significantly.Single application of iron,zinc,and selenium fertilizers all increase the activity of AI and NI in the fruit,promote the decomposition of sucrose,increase the concentration difference between the phloem and the fruit,and facilitate the unloading of sucrose,thereby increasing the content of reducing sugars.The activities of SS,SPS,AI and NI of combined application of zinc and iron were significantly enhanced compared with basal application of Zn fertilizer.Under the basal application of Se fertilizer,the exogenous spraying of Zn and Fe fertilizers significantly enhanced the activity of SS in the fruit,and significantly reduced the activities of SPS,AI,and NI,which promoted the synthesis of sucrose and inhibited its decomposition,which was more conducive to the accumulation of sucrose.5.Compared with the control,exogenous iron and selenium fertilizers are more conducive to increasing the sweet amino acid,essential amino acid content and E/T,E/N in tomato fruit,which is closer to the FAO/WHO standard,thereby promoting the improvement of protein quality.On the basis of basal application of Zn fertilizer,spraying Fe fertilizer on the leaves significantly increased the content of total amino acids and savory amino acids,but reduced essential amino acids.On the basis of basal Se fertilizer,foliar spraying of Zn and Fe fertilizers made the total amino acids,essential amino acids,umami amino acids and sweet amino acids all significantly decreased.6.Compared with the control,exogenous iron,zinc,and selenium fertilizers can increase the content and types of tomato flavor substances;On the basis of basal application of Zn and Se fertilizers,foliar spraying of Fe and Zn fertilizers found that the combined application of zinc-iron,selenium-zinc,and selenium-iron is more conducive to the content of flavor substances in tomato fruits and improves the flavor quality of crops.The specific expression is Zn（R）+ Fe（L）> Se（R）+Zn（L）>Se（R）+Fe（L）.The results of principal component analysis show that exogenous iron,zinc,and selenium have a significant promoting effect on the growth and development of tomato fruits and the improvement of nutritional quality,especially the combined application of zinc,iron,selenium and zinc.