Ultraviolet-B radiation and nitrogen effects on growth and yield of maize under Mediterranean field conditions

The effects of an increase in UV-B radiation on growth and yield of maize ( Zea mays L.) were investigated at four levels of applied nitrogen (0, 100, 200 and 300 kg ha(-1) of N) under Mediterranean field conditions. The exper iment simulated a 20% stratospheric ozone depletion over Portugal. Enhanced W-B and N deficiency decreased yield and total biomass production by 22-49 %. High UV-B dose reduced yield, total biomass and growth of N-fertilized m aize plants but did not affect N-stressed plants to the same extent. The re sponse of grain yield to N was smaller with enhanced UV-B radiation. The un derlying mechanisms for these results are discussed. (C) 2000 Elsevier Scie nce B.V. All rights reserved.