Effects Of Different Levels Of Soil Organic Matter On Photosynthesis Of Leaves, Sugar And Organic Acid Metabolism As Wellas Quality In Apple Fruit

Soil organic matter is not only one of the important indicators to measure the soil fertility,but also the key to achieve high quality and yield in apple,so the research of different levels of soil organic matter on photosynthesis,fruit quality and internal sugar,acid metabolism of apple has great significance of orchard organic fertilization,improving fruit quality and production.The study was carried out by applying three levels of soil organic matter including 3%,5%and 7%on potted apple（Malus domestica Borkh.Cv.Gala）,during the whole growth period,by detecting the photosynthetic and chlorophyll fluorescence parameters of leaves,the content of soluble sugar and acid in the fruit,the related enzyme activities in the sugar and acid metabolism and several related parameters of fruit quality,in order to explain the relationship between organic matter and fruit quality.Obtained results of this study were as follows:1.After application of organic matter,the physical and chemical properties of soil had dramatically improved,soil microbial bacteria,fungi and actinomycetes activities,number of macroelement and microelement elements were also increased,the inclusion of soil were enriched.2.Among the three levels of soil organic matter treatments,7%cultivated plants had the highest photosynthetic properties,net photosynthetic rate（Pn）,transpiration rate（Tr）,intercellular CO₂ concentration（Ci）and stomatal conductance（Gs）all had significant difference with 5%and 3%.The leaf chlorophyll a,chlorophyll b,organic carbon content and specific leaf weight were also increased.Meanswhile the initial fluorescence of chlorophyll（F₀）,maximal fluorescence yield（F_m）and maximum photochemical efficiency（F_v/F_m）were relatively hight,that means increasing the soil organic matter content can improve the photosynthetic characteristics of plants.3.By determining the fructose,glucose,sorbitol and sucrose content of fruit and related enzymes activities of sucrose and sorbitol metabolism,we found that differences existed among the three treatments,and 7%SOM treatment had the highest sugar content and enzyme activities.In terms of this four soluble sugar,sorbitol content was heavily affected by organic matter,thus the differences between the groups of related enzyme activity of sorbitol metabolism were significant.There were no significant difference between 5%and 7%in data of sucrose content,but obvious difference occurred in sucrose metabolism related enzymes activities between the groups.The fructose and glucose content also increased with the rise of SOM content,but no significant difference between 3%,5%and 7%.The malic acid is the main organic acids in apple fruit,by measuring malic acid content and related enzymes activities,the results showed that the malic acid content was less affected by SOM,but the synthesis pathway of malic acid related enzyme cyMDH was great influenced,PEPC was influenced the second,whereas degradation enzyme ME and PEPCK were all affected heavily.There were significant difference among the three treatments,and7%showed the best performance.4.With the rising of soil organic matter content,the fruit size,skin color,flavor,and the content of inclusions were improved,the content of element Ca and Mg were increased too.At the same time,microelement of Fe,Mn,Zn,Cu content were also increased in proportional to the content of soil organic matter.The results of the study showed that the organic matter can improve the flavor and quality of fruit and with the increasing of soil organic matter,the nutrient content of fruit were also increased.In generally,soil organic matter by improving soil physical and chemical properties,enhancing photosynthetic performance and then significantly influenced the sugar acid metabolism and fruit quality.