TRANSMISSION OF UV-IRRADIANCE INTO NECTARINE FRUIT

With the global depletion of the ozone layer, leaves and fruits are in creasingly exposed to UV-irradiance on the tree. Some fruits are addit ionally exposed postharvest to artificial germicidal W-irradiance, lea ding to a cumulative effect. This paper examines the transmission of U V-light (200-400 nm) by the peel of ripe nectarine fruit using UV/VIS spectrophotometry to aid understanding of UV-effects and assess the se nsitivity of the peel to UV wavelengths. Yellow peel of nectarine frui t transmitted less than 0.1 % in the UV-C range of 220 to 280 nm. With longer wavelenghts, UV-light transmission increased slowly from 0.4 % at 284 nm to 1.6 % at 320 nm and, in the UV-A region, progressively f rom 1.9 % at 330 nm to a maximum of 13 % of incident irradiance at 400 nm. Red peel of nectarine fruit transmitted less than 0.1 % of UV-C a nd UV-B light, but up to 0.9 % of incident UV-A light at 400 nm. Conve rsely, UV-absorption of nectarine peel decreased with longer wavelengt hs. Hence, fruit parenchyma is more affected by UV-irradiance at wavel engths above ca. 280 nm and underneath yellow than underneath red peel .