Effects Of UV-B Radiation Enhanced On Carbon And Nitrogen Distribution And Fruit Quality Of Peach Under Protected Culture

The experiment had been carried out in Shandong Agricultural University fromDecember2009to June2011with6-year-old greenhouse-grown ‘chunjie’ peaches （Prunuspersica cv. Chunjie）. With the different intensity UV-B radiation manually setted, we studiedthe effects of UV-B radiation enhanced on physiological characteristics and fruit quality,discussed the effects on carbon and nitrogen distribution of protected peach. The main resultswere as follows:1. UV-B radiation enhanced leaded to the significant change on physiologicalcharacteristics of leaves of protected peach. In the range of0μW· cm^-2to28μW· cm^-2,ehanced UV-B radiation reduced the leaf area. Meanwhile, physiological metabolisms ofleaves of protected peach have undergone adaptive changes. Ehanced UV-B radiationlowered the content of chlorophyll a; the effect on the content of chlorophyll b were differentin different developmental stage; added to the the relative conductivity; increased the contentof MDA and falconoid; improved the activity of POD and SOD. These effects on the leaveswere more significant with the increase of intensity of the UV-B radiation.2. Effects of UV-B radiation on assimilates translocation and distribution in fruitingshoot of protected peach were notable. The ability to compete for14C-assimilates wereincreased in fruits with supplemented UV-B radiation that caused an increase in distributionof14C-assimilates. And the translocation and distribution of14C-assimilates in peachesappeared to be affected by the period of fruit development. During rapid expansion stage offruit, the54.67%of total14C-assimilates was distributed to the fruit under low intensitytreatment (14μW·cm^-2). Medium intensity treatment (21μW·cm^-2) caused the58.98%of total14C-assimilates to allocate into various vegetative organs. In hardcore stage, the competitionof fruit treated with high intensity treatment (28μW·cm^-2) for14C-assimilates was strongest;accounting for31.73%of total assimilates. In fruit coloring stage, the accumulation of87.88%of total14C-assimilates in fruit was significantly observed under medium intensitytreatment (21μW·cm^-2).3. Effects of UV-B radiation on¹⁵N urea absorption, utilization and distribution infruiting shoot of peach under protected culture were significant. The Ndff levels of thesampled organs are increased under the UV-B irradiation, and are distinctively influenced atvarious phonological phases. At the fruit-swelling stage, the highest Ndff levels of most organs are detectable under high intensity of UV-B radiation condition, except for those ofbiennial branches under the low intensity of UV-B radiation. At the core-hardening stage, thehighest Ndff levels in vegetative organs are examined under either moderate or high intensityof UV-B radiation condition, and yet the low intensity of UV-B radiation condition isresponsible for those in both flesh and stone. At the fruit-coloring stage, the moderateintensity of UV-B radiation condition turns out to contribute to the highest Ndff levels inorgans determined.It indicates that the UV-B radiation raise¹⁵N utilization efficiency notably by bearingbranches. At the fruit-swelling stage, the high intensity of UV-B radiation condition exertssignificantly distinct consequences on¹⁵N distribution to the tested organs. At fruit-swellingstage, higher intensive UV-B radiation significantly raised the utilization efficiency of¹⁵N（50.28%）, while at stages of core-hardening and fruit-coloring, the utilization efficiencies of¹⁵N peaked under moderate intensity of UV-B radiation condition, with significant increaseby83.99%and105.56%compared to control, respectively.At various phonological phases, the influence of enhanced UV-B radiation on¹⁵Ndistributions are notable different from each other. At the fruit-swelling and fruit-coloringstages,¹⁵N is mostly distributed to control leaves （13.44%and8.97%, respectively）, whilethe¹⁵N distributions to other organs are promoted by the UV-B radiation. At thecore-hardening stage, both moderate and high intensity of UV-B radiation condition favor the¹⁵N distribution to leaves, while low intensity of UV-B radiation is beneficial for¹⁵Naccumulation in other organs.4. Enhanced UV-B radiation can improve the fruit quality of peach under protecedculture notablely. Enhanced UV-B radiation increased the fruit weight, added to the contentof dry material and soluble solids; improved the content of soluble sugar and starch, reducedthe content of titratable acidity and improved the sugar to acid ratio. In addition enhancedUV-B radiation increased the content of carotenoid and anthocyanin, which were conduciveto fruit coloring. Single fruit weight, the content of dry material, carotenoid and anthocyaninwere the highest with the treatmen of28μW·cm^-2. The content of soluble solids and solublesugar, the sugar to acid ratio, and the content of starch were the highest under thesupplemental UV-B radiation of21μW·cm^-2.