Effects Of Different Potassium Application Levels On Fruit Quality And Sugar Metabolism Of Fig Fruit

Ficus carica L.is a plant of Ficus in the Moracene family.It is easy to cultivate and has strong adaptability.It is particularly suitable for planting in Fujian coastal areas where there is sufficient light,no severe cold in winter,and sea breeze and fog.It is a new type of food therapy and health care fruit with high nutrition,high medicine and multiple utilization.Although"Bojihong"fig is the main variety in Fujian Province,it is easy to be influenced by many factors because of its short introduction time and imperfect cultivation techniques.The sugar content in the fruit is one of the most important factors that affect the quality and flavor of the fruit.The quality formation of figs mostly depends on the accumulation of sugar in the fruit.Potassium is one of the essential nutrients in the growth and development of fig,which plays an important role in promoting the growth and development of fruit,improving the quality of fruit and enhancing the resistance of fruit.There are many reports about the effect of increasing potassium fertilizer on fruit quality and sugar metabolism in apple,pear,Bayberry and other fruit trees,but there are few reports about the effect of increasing potassium fertilizer on fruit quality,sugar metabolism and related enzyme activity in fig.In this experiment,2-year-old‘Bojihong'fig was used as the test material.Under the premise of conventional cultivation and management,four levels of K₂SO₄ were added to carry out the control experiment.By measuring and analyzing the weight,size,color parameters and hardness of single fruit,the internal quality of soluble solids,soluble sugar,titratable acid,vitamin C,soluble protein,ratio of sugar to acid and the activity of enzymes related to sugar metabolism,the regulation mechanism of different potassium application levels on the quality and sugar metabolism of fig fruit was investigated.The main results are as follows:1.Compared with the control,potassium fertilizer significantly increased the weight,hardness,soluble sugar and vitamin C content of fig fruit,and decreased the titratable acid content,among which K2?250g/plant?was the best.When fruit matured,the appearance quality of fruit such as longitudinal diameter,transverse diameter,single fruit weight and fruit firmness increased by 26.88%,14.6%,31.0%and47.6%respectively,and the ratio of soluble solids,vitamin C,soluble protein and sugar to acid increased by 30.5%,11.1%,25.7%and 65.7%,respectively.Compared with K2,K3?375g/plant?with the highest potassium application rate had lower fruit weight,fruit size,hardness,soluble sugar and vitamin C content,and higher titratable acid content.It can be concluded that appropriate application of potassium?K2?can promote the formation of fig fruit quality.With the increase of potassium application,fruit quality tends to decrease.2.With the growth and development of fig fruit,the contents of chlorophyll and carotenoid in the pericarp gradually decreased,and the content of anthocyanin gradually increased,and the content of pigments was highly correlated with the content of soluble sugar.Adding potassium fertilizer accelerated anthocyanin synthesis and degradation of chlorophyll and carotenoids in fig peel,increased a^*value and b^*value of fruit color parameters,and increased peel surface color,resulting in a decrease in L^*value?brightness?.The anthocyanin content in the pericarp of fig with appropriate potassium application?K2?was the highest,and the fruit color was the best.Excessive potassium application?K3?was not conducive to anthocyanin accumulation in the pericarp of fig.3.Adding potassium fertilizer increased the fructose,glucose and sucrose content of fig fruit during the whole development period.Among them,K2 treatment had the best effect.The contents of fructose,glucose and sucrose were 38.3 mg g^-1,40.2 mg g^-11 and 0.13 mg g^-1,respectively,which were 25.5%,32.0%and 28.6%higher than the control.Potassium fertilizer increased the activity of decomposition direction of AI,NI and SS,especially in the middle and late stages of fruit development,which promoted the accumulation of fructose and glucose during fruit ripening stage,increased the activity of SPS at all stages of fruit development,promoted the accumulation of sucrose,and the effect of K2 was the most significant overall.However,with the increase of potassium application,the effect of promoting sugar accumulation in fruits became worse.4.In the early stage of fig fruit development,potassium fertilizer promoted starch synthesis.In the late stage of fruit development,potassium fertilizer increased the activity of alpha-amylase and beta-amylase gradually and maintained at a high level,which promoted starch decomposition and soluble sugar accumulation in fig fruit,among which K2 treatment had the most significant effect.