EFFECTS OF SOLAR UV-B IRRADIATION ON VEGETATIVE AND GENERATIVE GROWTHOF BROMUS-CATHARTICUS

The effects of three different solar W-B levels (no UV-B, 80 and 90% o f ambient W-B) on the growth, pigmentation, seed yield and seed qualit y of Bromus catharticus were studied. The results indicated that W-B h ad a slight overall positive effect on the vegetative biomass producti on of Bromus. Morphology was more sensitive to UV-B showing reduced pl ant height and increased tillering by UV-B. Generative growth was much more sensitive to W-B than vegetative growth: the number of seeds and the dry weight per seed almost doubled from the control to the 90% UV -B treatment. The germination of seeds from the different treatments w as not significantly different under optimal conditions, nor was the C and N content. There was no evidence for increased flavonoid producti on or leaf weight ratio (LWR) in response to UV-B. Natural UV-B levels appeared not to damage Bromus, but only to result in changes in alloc ation that could be positive for the species reproduction in the wild. (C) 1998 Elsevier Science B.V. All rights reserved.