| We sprayed on the13-year-old ‘Gala’ and ‘Fuji’ grafted Malus hupehensis with zincsulfate and sugar alcohol zinc at four developmental stages (before bud break, at three weeksafter bloom, at the termination of spring shoots, during the fruit expansion). The appleorchard (116°50’E,36°14’N) was located in Chaoquan Town, Shandong Province. Theeffects of zinc sprays before bud break on the growth and development of flowers and leaveswas studied. We also determined the leaf and fruit zinc and net photosynthetic rate. Weanalyzed the external and inner quality of fruit, which includes the average weight, fruit shapeindex, color, firmness, soluble solids, soluble sugar, titratable acid, Vc and anthocyanincontents of fruits at maturity. The changes of reducing sugar contents and activities ofcarbohydrate metabolism enzymes were observed. The changes in the activities of Sorbitoldehydrogenase, sorbitol oxidase, sucrose synthase cleavage, acid inverse and neutral inversewere analyzed. We explored the reasonable stages of improving fruit quality and zincbiofortification measures with aerial zinc sprays on apple trees basic on the above research,and clarified the preliminary mechanism of zinc affecting apple fruit quality.(1) Aerial zinc sprays promoted the development of flower. The zinc sprays before budbreak significantly increased filament length, ovary weight and flower zinc content of ‘Gala’and ‘Fuji’. The effects on ovary weight of sugar alcohol zinc treatments were better than thoseof zinc sulfate treatments. In2012year, the flower zinc contents of sugar alcohol zinctreatments was higher that of zinc sulfate.(2) Aerial zinc sprays promoted the development of leaves and improved photosynthesiscapacity. All the zinc treatments significantly increased the leaf area of ‘Gala’, but there wereno significant differences between the area of the treatment at the termination of spring shootsand the control for ‘Fuji’. All the treatments significantly increased in leaf area index, and theleaf area index of treatments administrated prior to bud break and at fruit expansion still remained high. All the treatments significantly increased the relative chlorophyll contents ofleaves of ‘Gala’ and ‘Fuji’ except that of the treatment at the termination of spring shoots. Allthe treatments significantly increased net photosynthetic rate of leaves of ‘Gala’, but for‘Fuji’ the treatment administrated at the termination of spring shoots did not increased netphotosynthetic rate of leaves.(3) Aerial zinc sprays significantly increased leaf zinc level and stimulated the uptake ofzinc and calcium by the fruit. For ‘Gala’, the zinc contents of leaves of the treatmentadministrated before bud break was higher than the control in the early stage, but not in thelate stage. The leaf zinc contents of the other treatments were higher than that of control in thewhole growth and development periods. For ‘Fuji’, zinc sprays before bud break and at threeweeks after bloom significantly increased the leaf zinc contents in the early stage, but not inthe late stage, and the other treatments significantly increased the leaf zinc contents in thewhole growth and development periods. All the treatments significantly increased the zinccontents of ‘Gala’ fruits, and the fruit zinc of the sugar alcohol zinc treatments increased morethan that of zinc sulfate treatments. There was high relevance between fruit zinc and fruitcalcium. Zinc sprays significantly increased fruit calcium contents, and did not increased thefruit iron and potassium contents.(4) Aerial zinc sprays promoted the development of fruit and improved the fruit quality.The treatment administrated at three weeks after bloom significantly increased the averageweight of ‘Gala’ fruit, and for ‘Fuji’ fruits, the treatments administrated at three weeks afterbloom and at fruit expansion significantly increased the average fruit weight. All thetreatments had no significant effect on the fruit shape index. The treatments administratedprior to bud break and at fruit expansion significantly improved the color of ‘Gala’ fruits, andall the treatments significantly improved the color of ‘Fuji’ fruits. The effects of sugar alcoholzinc were better than zinc sulfate on improving the color of fruits. The treatmentsadministrated prior to bud break and at fruit expansion significantly increased the firmness of‘Gala’, and for ‘Fuji’ fruits, the treatments administrated prior to bud break and at three weeksafter bloom significantly increased the firmness. Also the effects of sugar alcohol zinc werebetter than zinc sulfate on firmness of fruits. The sugar alcohol zinc treatments administratedbefore bud break and at three weeks after bloom, and the treatments of both zinc form administrated at fruit expansion significantly increased the soluble solids of ‘Gala’ fruits, andfor ‘Fuji’ fruits, both zinc-form sprays before bud break and other sugar alcohol zinctreatments significantly increased the soluble solids. All the treatments significantly increasedsoluble sugar of ‘Gala’ fruits except the treatments administrated at the termination of springshoots, and all the treatments significantly increased the soluble sugar of ‘Fuji’ fruits. Zincsprays at three weeks after bloom and at fruit expansion significantly decreased the titratableacid of ‘Gala’ fruits, and for ‘Fuji’ fruits, the zinc sprays at three weeks after bloom and atfruit expansion and sugar alcohol zinc sprays at the termination of spring shoots significantlydecreased the titratable acid. All the treatments significantly increased Vc of ‘Gala’ fruitsexcept the treatments administrated at the termination of spring shoots, for ‘Fuji’ fruits, all thetreatments significantly increased Vc except the zinc sulfate sprays at the termination ofspring shoots. Also the effects of sugar alcohol zinc were better than zinc sulfate on Vc offruits. The treatments administrated at fruit expansion significantly increased anthocyanincontents of ‘Gala’ fruits, for ‘Fuji’ fruits all the treatment significantly increased anthocyanincontents and the sugar alcohol was better than zinc sulfate.(5) Aerial zinc sprays stimulated the translocation of photosynthate to fruit by increasingthe sink capacity which resulted from the increase of activities of sugar metabolism enzymes.The reducing sugar of fruit of zinc treatments was of no significant difference with the controlat the early stage, but significantly increased100-130days after bloom. Sorbitoldehydrogenase (SDH) activity of the treatments administered prior to bud break and at threeweeks after bloom was significantly higher at young fruit stage. The SDH activity oftreatments administered when the spring shoots stopped growth was higher than the controlduring fruit expansion period. The SDH activity of treatments administered at fruit expandingstage was higher than the control during fruit expansion period. The sorbitol oxidase (SOX)activity of all the treatments was no significantly different compared with the control. Thetreatments administered prior to bud break and at three weeks after bloom significantlyincreased sucrose synthase (SS) cleavage activity at young fruit stage. The acid inverse (AI)of treatments administered prior to bud break and at three weeks after bloom was more highthan the control at young fruit stage. The treatment administered at fruit expanding stagesignificantly increased AI activity at mature stage. There were no effects on the neutral inverse (NI) between the Zn treatments and the control. At mature stage, reducing sugar, zinccontents and AI activity, SDH activity was of high relevance. |
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