Variation in transpiration, leaf RWC and WUE among wild barley ecotypes at different soil water contents. (A-D) Pictures of ecotypes B1K2 (A and B) and B1K30 (C and D) under well-irrigated condition or full field capacity - 80% SWC (A and C) and drought condition - 30% SWC (B and D). (E) Average mid-day whole-plant transpiration of B1K2 and B1K30 under normal (80% soil moisture content) and drought (30% soil moisture content) conditions. (F) Average mid-day leaf RWC of B1K2 and B1K30 under normal and drought conditions. (G) The WUE of each ecotype as determined by fitting a linear curve for the ratio between the plants’ cumulative weight gain and cumulative transpiration. The error bar and asterisk in (E) and (F) represent standard error (±SE) and significance differences (t test, p <0.05) among the ecotypes, respectively. Data (E and F) are means of four independent repetitions.