Intraspecific variation in sensitivity to ultraviolet-B radiation in maizegrown under field conditions - II. Physiological and biochemical aspects

The effects of enhanced UV-B radiation on the gas exchange rates, chlorophy ll fluorescence, pigmentation, soluble sugars and carboxylation enzymes of eight maize (Zea mays L.) cultivars grown under Mediterranean field conditi ons were studied. Supplementary UV-B radiation reduced photosynthetic capac ity as a consequence of damage to PSII, increased stomatal resistance, lowe red RUBISCO and PEPcase activities and reduced chlorophyll and carotenoid c ontent. Chlorophyll a levels decreased to a greater extent than those of ch lorophyll b. Transpiration rate and water-use efficiency were also decrease d by UV-B. The accumulation of UV-B absorbing compounds was not stimulated by ultraviolet radiation. The underlying mechanisms for these results are d iscussed. Apart from these general behaviour patterns, considerable genotyp ic differences exist within maize cultivars. Further long-term field studie s are necessary to assess the interaction between W-B exposure and climate variables, as well as with agronomic practices. (C) 1999 Elsevier Science B .V. All rights reserved.