Effects Of Spraying Calcium And Mulching On Fruit Quality And Puffing Degree Of ’Nanfeng Tangerine’

‘Nanfeng tangerine’(Citrus reticulita Blanco cv.Nanfeng tangerine)is an ancient cultivar,its fruits are golden yellow and unique flavor,which has been deeply loved by people.However,the fruit tends to puffing,which reduces its economic value.In this study,‘nanfeng tangerine’ was used to spray Ca at different stages of fruit growth and delay cultivation under the condition of tree tray mulching treatment.These results provide the basis for solving the fruit puffing of ‘nanfeng tangerine’.The results were as follows:1.Calcium ions were mainly transported to the fruit by xylem of fruit stalk.The fluorescence signals of calcium ions were the strongest at young fruit stage,the ability to transport calcium ions declined with the fruit growth,and decreased sharply after entering mature stage.The fluorescence signals of spraying Ca+IAA were stronger than that of spraying Ca.2.Calcium ions in peel cells were mainly distributed in yellow and white cortex,the fluorescence signals were stronger when spraying Ca twice or adding IAA,the effect was obvious in young fruit stage from May to June,and the synergistic effect between Ca and IAA was significant.3.The activity of POD and PPO in the peel increased gradually with the fruit development,and was inhibited by spraying Ca or Ca+IAA.The activity of SOD and CAT increased rapidly in young fruit stage,reached the peak in expansion stage,and then showed a downward trend,and spraying Ca or Ca+IAA was beneficial to maintaining higher SOD and CAT activity in the peel.The activity of PG,PME and Cx in the peel showed a increased trend on the whole,and were inhibited by Ca or Ca+IAA.MDA content was on the rise with the fruit development,and increased rapidly at maturity stage,and reduced by spraying Ca.Spraying Ca + IAA was better than spraying Ca in young fruit stage from May to June,and spraying twice was better than once.4.The fluorescence signals of free calcium in fruit stalk werestronger than that in the peel,and in the xylem than in the phloem.At the same time,there was a significant negative correlation between the volume of puffiness rate and the intensity of fluorescence signals in the yellow or white cortex.The signals of spraying Ca+ IAA were the strongest in young fruit stage from May to June.5.Spraying Ca at different stages had different effects on preventing the puffing,and,especially at young fruit stage,could significantly increase the TSS,TA,VC contents of mature fruits,the peel percentage,longitudinal and transverse diameter,TSS/TA.The effect of preventing puffing was more significant after adding IAA.Moreover,the volume of puffiness rate was positively correlated with single fruit weight,the peel percentage,longitudinal and transverse diameter,TSS/TA,and negatively correlated with TA and Vc.6.Spraying Ca at different stages improved CAT and SOD activity,reduced MDA content and POD,PPO,PG,PME,CX activity,The above effects were more significant when IAA was added,among which,the effect was best in the young fruit stage,followed by the expansion stage.Meanwhile,the volume of puffiness rate was negatively correlated with SOD and CAT activity,but positively correlated with POD,PPO,PME,PG,Cx activity and MDA content.7.The mulching treatment reduced the single fruit weight,peel percentage,longitudinal and transverse diameter and TSS/TA,but increased the content of TA and Vc.The volume of puffiness rate was positively correlated with the soil humidity and negatively correlated with the content of TA and Vc in fruits.The volume of puffiness rate gradually deepened with the ripening,all mulching treatment could reduce the volume of puffiness rate to varying degrees.The effect of garden cloth treatment on preventing puffing was the best,followed by reflective film,carpet,garden cloth+water-retaining agent treatment.Therefore,during the fruit growth process,calcium ions were mainly transported to fruit by xylem of fruit stalk,and distributed in the yellow and white cortex in the peel.Spraying Ca during the young fruit period from may to June was more conducive to the transport of calcium into the fruit.Spraying Ca strengthened the ability of the antioxidant enzymessuch as CAT and SOD,reduced the hydrolase activity of PG,PME and CX in the cell wall,thus maintained the toughness and strength of the peel,and effectively prevented the occurrence and aggravation of puffing.Spraying Ca+IAA at young fruit stage had the best effect on preventing puffing and improving fruit quality.The covering treatment could reduce the volume of puffiness rate with the complete ripening of fruit,among which,the ground cloth had the best effect on preventing puffing.