Effects of UV-B Radiation on 15N urea absorption, utilization and distribution in fruiting shoot of peach under protected culture

This study was conducted to determine the effects of UV-B radiation on 15N absorption, utilization and as well as distribution in 2 year-fruiting shoot of peach under protected culture. The zero (control), low, moderate and high intensities of UV-B radiation were conducted on six-year-old greenhouse-grown chunjie peaches (Prunus persica cv. Chunjie). Leaves were fed with 15N-labeled urea at the various stages of fruit development. Subsequently, leaves, fruits and branches were respectively harvested for the determination. The Ndff levels of the sampled organs are increased under the UV-B irradiation, and are distinctively influenced at various phonological phases. At the fruit-swelling stage, the highest Ndff levels of most organs are detectable under either the moderate and high intensity of UV-B radiation condition, except for those of biennial branches under the low intensity of UV-B radiation. At the core-hardening stage, the highest Ndff levels in vegetative organs are examined under either moderate or high intensity of UV-B radiation condition, and yet the low intensity of UV-B radiation condition is responsible for those in both flesh and stone. At the fruit-coloring stage, the moderate intensity of UV-B radiation condition turns out to contribute to the highest Ndff levels in organs determined. It indicates that the UV-B radiation raise 15N utilization efficiency notably by bearing branches. At the fruit-swelling stage, the high intensity of UV-B radiation condition exerts significantly distinct consequences on 15N distribution to the tested organs. At fruit-swelling stage, higher intensive UV-B radiation significantly raised the utilization efficiency of 15N (50.28%), while at stages of core-hardening and fruit-coloring, the utilization efficiencies of 15N peaked under moderate intensity of UV-B radiation condition, with significant increase by 83.99% and 105.56% compared to control, respectively. At the fruit-swelling and fruit-coloring stages, 15N is mostly distributed to control leaves (13.44% and 8.97%, respectively), while the 15N distributions to other organs are promoted by the UV-B radiation. At the core-hardening stage, both moderate and high intensity of UV-B radiation condition favor the 15N distribution to leaves, while low intensity of UV-B radiation is beneficial for 15N accumulation in other organs. Taken together, at various phonological phases, the characteristics of 15N absorption, utilization and distribution of the tested organs seem dependent upon their sensibilities to the UV-B radiation.