the effects of carbon dioxide, ultraviolet radiation and moisture alterations on yield and metabolic compounds in bread wheat (triticum aestivum l.)

drought, ultraviolet radiation and atmospheric co2 are some three environmental factors that seriously affect future food security. the objective followed in the present research was to study the effect of two levels of carbon dioxide (400 and 900 ppm), ultraviolet radiation (uv a, b and c with intensities of 18, 25 and 40 microw.cm-2 respectively) and water deficit (%100 and %60 of field capacity) on yield and some metabolic leaf compounds in bread wheat (cv. pishtaz). results showed that ultraviolet radiation enhancement increased anthocyanin, flavonoids and carotenoids content of bread wheat leaf while reducing grain yield. but leaf anthocyanin and flavonoids decreased when co2 increased. water deficit also decreased flavonoids and carotenoids of bread wheat leaf. ultraviolet radiation and carbon dioxide enrichment decreased leaf carbohydrate while water deficit exerting no effect on it. leaf flavonoids increased under high ultraviolet radiation and water deficit but decreased through carbon dioxide enhancement. in total, high ultraviolet radiation decreased leaf chlorophyll content (a and a+b). but it did not follow the same trend at different levels of water deficit and carbon dioxide concentrations. leaf soluble proteins decreased when ultraviolet radiation, carbon dioxide concentration and water deficit increased. finally the results indicated that leaf soluble carbohydrates, proteins and generally nutrient value of cereals inclding bread wheat will decrease in the future with microclimatic and environmental variations and as well with rise in greenhouse gases and ultraviolet radiations. in could be predicted that in the future, wheat production will be diminished as a result of low plant vigor under adverse microclimatic changes.