Nutrition Diagnosis And Cold Resistance Analysis Of The Main Longan Varieties In Chongqing Of China

Longan(Dimocarpus longan Lour)is a subtropical economic fruit tree that originally lived in tropical areas of southern China,such as provinces of Hainan,Yunnan,Guangxi,and Taiwan.Chongqing,a big mountain city located at the edge area of South Subtropical Zone in China,has gradually increased longan planting area in Chongqing due to the warming weather in recent decades.Moreover,Chongqing longan belongs to late ripening fruit with good quality and sales in off-peak seasons which brings economic benefits for fruit farmers.Therefore,longan cultivated in Chongqing is also growing more and more.However,abnormal climate such as rainy low temperatures,sleet,and even extreme low temperatures occasionally taken place in Chongqing winter.This weather condition would cause damage to the leaves and flower buds of longan,and it would also easily cause nutritional disorder of longan trees.In addition,Chongqing is a mountainous area with complex planting terrain where rural labor force be lack of,which makes the elderly fruit farmers high extensive management of longan,and even cause the orchard soil nutrient depletion and nutrient imbalance as well as soil physicochemical property change.These many factors decrease the fruit yield and quality and result in on-year and off-year phenomenon taking place.Therefore,screening cold-resistant varieties and tree nutrition diagnosis have become the very important problems should be solved now.In this study,four orchards in Yongchuan Qu and Fuling Qu,Chongqing,were used as the research sites.Seven main longan varieties,"Shuguan","Chu Liang","Shixia","Dawuyuan","Yutanben","Yellow Shell",and "Jinqiu No.1" were used as research materials.In November 2018,samples were taken off to diagnose the nutritional status of soil and leaves in Chongqing longan,and to analysis the relationship between them.and to observate leaf tissue structure of Chongqing Longan in autumn and winter.Three batches of samples were taken off respectly in November2018,January 2019 and March 2019,in order to study the change rule of physiological and biochemical characteristics of longan leaves,the change of mineral nutrient element content in autumn and winter leaves,and the difference of nutrient element content in different longan varieties.The test results are as follows:1.Analysis of Nutritional Diagnosis of Main Longan Planted in ChongqingAfter a comparative analysis with the appropriate standard of longan nutrients,it is found that Chongqing longan generally lacks trace elements,such as Fe,Cu,Mn,B,especially Mn and B.The content of trace elements affects the growth and metabolism of plants,so Chongqing Longan Orchard should appropriately supplement the corresponding trace elements by fertilizing or spraying drugs.2.Correlation Analysis of Nutrition Elements in Main Longan Planted in ChongqingThe correlation between p H,organic matter and available elements in soil is significant,such as organic matter and available N,P,K are positively correlated.There is also a certain correlation between nutrients in longan leaves,such as N is positively correlated with Mg,S,Fe.In addition,there is also a complex relationship between soil nutrients and leaf mineral nutrients in Chongqing longan orchards.It shows that the elements can restrict and promote each other,which provides a theoretical basis for guiding the rational fertilization of fruit farmers.3.Dynamic Changes of Mineral Nutrition in Leaf of Chongqing Longan During OverwinteringThe changes of P,K,Ca,Mg,Fe,Cu,Mo and other nutrients contained in the leaves of longan have a certain regularity,and the changes of other nutrient elements are not significant.Related.In addition,there is a certain relationship between the longan leaf tissue structure and its physiological and biochemical and leaf mineral nutrition status,such as N is positively correlated with chlorophyll.4.Longan cold resistance analysisThis test describes the characteristics of the anatomical structure of longan leaves,and measures the thickness of leaves,veins,upper and lower epidermis,fence tissue and other indicators of seven varieties of longan.The results showed that the anatomical characteristics of different varieties of longan were not consistent.Chlorophyll,electrical conductivity,malondialdehyde,soluble sugar,soluble protein,SOD,POD,and CAT of the longan leaves collected three times from November2018 to March 2019 changed regularly in different periods.Among them,the content of chlorophyll,soluble sugar,soluble protein,SOD,POD,and CAT all showed an increasing trend in the coldest January of winter,which was positively related to cold resistance.Conductivity and malondialdehyde increased with the decrease of temperature,and decreased with the increase of temperature,which was negatively correlated with cold resistance.The leaf thickness and physi-biochemical indexes can be used as the cold resistance parameters of longan.The cold resistance of seven longan varieties were evaluated by Excel2010 and Spss19.0 software.The results showed that the cold resistance descending order were Shixia,Shuguan,Chuliang,youtanben,Jinqiu No.1,Huangke,Dawuyuan.