the effects of water deficit on crop yield and the physiological characteristics of barley (hordeum vulgare l.) varieties

the effects of water deficit on grain yield, yield components and the physiological char-acteristics of barley (hordeum vulgare l.) varieties were studied in a split plot design dur-ing the 1999-2000 growing season in karaj, iran. five irrigation levels [0, 25, 50, 75, and 100% crop water requirements (cwr)] and six barley varieties karoon kavir , rei-hani(drought tolerant), torkman , c-74-9 (intermediate) , kavir badia and gorgan-4 (2 rowed type, drought sensitive) were arranged in the main plots and sub plots respectively. results showed that water deficit induced stress and this decreased the grain yield and yield components. water deficit increased the canopy temperature and those varieties showed a higher canopy temperature under non-stress conditions, performed better un-der drought conditions. severe stress reduced the chlorophyll content (spad values) con-siderably, but the differences were not significant between the 50, 75 and 100% cwr treatments. in addition, no significant differences were observed in the chlorophyll con-tent of barley varieties under drought conditions. the effect of irrigation on the photo-chemical efficiency of photosystemii (fv/fm) and the other fluorescence parameters for all varieties were significant. although the fv/fm values were not significant in barley varie-ties at any level of irrigation, in general karoon kavir and reihani varieties showed a better performance under water deficit conditions. proline content was significantly dif-ferent in various irrigation treatments, but its accumulation at any level of irrigation did not differ significantly in barley varieties. it was concluded that the higher canopy tem-perature (less negative t) under well irrigated conditions and higher grain yield, 1000-grain weight, fv/fm values under water stress conditions could possibly be the proper cri-teria for screening the drought tolerant barley genotypes under field or laboratory condi-tions.