EFFECTS OF ENHANCED UV-B ON GROWTH AND YIELD OF 2 SYRIAN CROPS WHEAT (TRITICUM-DURUM VAR. HORANI) AND BROAD BEANS (VICIA-FABA) UNDER FIELD CONDITIONS

The effects of enhanced W-B (280-320 nm) on the different phenological stages of a drought-resistant cultivar of wheat (Triticum durum var. Horani) and a drought-sensitive cultivar of broad beans (Vicia faba) u nder field conditions were investigated. Both species were exposed to a daily W-B dose 20% above the ambient UV-B simulating a 10% ozone red uction from germination to harvest. This dose ranged between 1.34 J/cm (2) at the beginning of the study and 6.33 J/cm(2) at the end of it. P lant height, tiller number, dry mass and leaf area in both species sho wed significant positive responses to UV-B treatment during the vegeta tive growth stages. At harvest, the seed mass of broad beans was nearl y equal in exposed and unexposed plants, whereas in wheat, the grain m ass and number of spikes increased significantly. This may support our hypothesis that a drought-resistant species (wheat) may exhibit great er protection against UV-B damaging effects compared to a drought-sens itive species (broad beans). (C) 1998 Elsevier Science B.V. All rights reserved.