Effects Of Exogenous Melatonin And Dopamine On Fruit Growth And Development Of Apple

Apple(Malus domestica)has a high commercial value because of its delicious taste and rich nutrition.Fruit quality is a key factor to measure the value of its commodities,and the shape of the fruit is also one of the important factors that determine the quality of its commodities.A well-controlled fruit shape and quality can further increase the value of its commodities.In actual production,orchard management is a complicated project.Improper management is prone to problems such as poor fruit shape and low fruit quality.Spraying plant growth regulators is a common method to improve fruit shape and fruit quality,but there may be a problem of pesticide residues in the fruit.Melatonin and dopamine are natural phytohormones found in plants.They naturally exist in apples and can solve the problem of pesticide residues in fruits.At present,there are relatively few studies on melatonin and dopamine regulating the entire growth and development process of apple fruit.This paper uses Fuji Nagafu No.2 and Yanfu No.3 as the test materials,during the germination,maturity and entire development stages of apples.External watering 100 μM melatonin and 100 μM dopamine to explore the effects of exogenous melatonin and dopamine on apple fruit growth and development can provide theoretical and technical basis for apple quality improvement and regulation.The main findings are as follows:1.Exogenous melatonin and dopamine can promote the growth of apple fruits.During the apple germination period and the entire development period,the application of exogenous melatonin and dopamine can promote the growth of the longitudinal and transverse diameters of the Fuji Nagafu No.2 and Yanfu No.3,and increase the fruit shape index and single fruit weight.Exogenous dopamine was applied during the germination period and the entire development period of the apple.The two treatments had the same effect on promoting fruit growth,and the promotion effect of exogenous melatonin during the entire development period was better than that of the germination period.In the external treatment of apples during the entire development period,the growth promotion effect of exogenous melatonin treatment was better than that of dopamine treatment,showing greater vertical and horizontal channels and single fruit weight.Compared with exogenous dopamine treatment,melatonin treatment has a better effect on promoting fruit longitudinal diameter elongation during the germination period and the entire development period of apples,and its fruit shape index value is higher than that of dopamine treatment.During the germination period and the entire development period of apples,the application of exogenous melatonin promoted the elongation of the stalks of Fuji Nagafu No.2 and Yanfu No.3,and the application of exogenous dopamine promoted the stalks of Fuji Nagafu No.2.Compared to the dopamine treatment,the melatonin treatment showed a relatively longer stalk.However,applying exogenous melatonin and dopamine only during the ripening period has no effect on the growth of the fruit.In addition,during the development of apples,there was no significant difference between exogenous melatonin and dopamine treatments on the number of apple ventricles and seeds,indicating that exogenous melatonin and dopamine treatments did not adversely affect the growth of apples.2.Exogenous melatonin and dopamine changed the soluble solids and titratable acid content of the fruit.After the application of exogenous melatonin and dopamine during the germination period and the entire development period,the soluble solids and titratable acid content of the mature fruit were reduced,but the solid-acid ratio was increased;in Fuji Nagafu No.2,compared with exogenous dopamine treatment,melatonin treatment showed relatively lower titratable acid and higher solid-acid ratio.The application of exogenous melatonin and dopamine during the ripening period both increased the soluble solid content of the fruit,but there was no significant difference at the 0.05 level.The fruit of Fuji Nagafu No.2 was used as the test material and stored at room temperature for 30 days after harvest.The results showed that both exogenous melatonin and dopamine treatments maintained a good soluble solid content and delayed the shelf life of the fruit.3.Exogenous melatonin and dopamine changed the color,texture and mineral element content of apple fruit.During the germination period and the entire development period of the apple,the application of exogenous melatonin and dopamine promoted the coloring of the fruit and improved the appearance quality of the fruit.The colorimeter results showed that the a* and CI values of the fruit were increased,and the L* and L* b* value;in the fruit of Yanfu No.3,the treatment effect of exogenous melatonin was better than that of dopamine treatment,showing a relatively higher color index CI value.Exogenous melatonin and dopamine change the texture of the fruit,increase the fruit skin extension,flesh brittleness and the flesh firmness,and reduce the fruit skin hardness.The treatment of exogenous melatonin and dopamine reduced the mineral concentration of fruit N and increased the mineral concentration of fruit P and K;applying exogenous melatonin during the germination period and the entire development period increased the mineral concentration of fruit Ca.4.Exogenous melatonin and dopamine affect the growth of apple leaves.Throughout the growth and development period of apples,the treatment with exogenous melatonin and dopamine increased the chlorophyll content in the leaves of Fuji Nagafu No.2 and Yanfu No.3,and increased the leaf weight of the leaves.5.In actual production,considering factors such as fruit growth and quality,time and labor costs,and comprehensive benefits,the application of exogenous 100 μM melatonin or dopamine at the beginning of the germination period has the most comprehensive improvement effect on fruit growth and quality.