THE EFFECT OF SOIL DROUGHT ON THE WATER USE EFFICIENCY IN SPRING BARLEY (HORDEUM VULGAREL.)

On the leaves of two modern varieties (Jersey and Malz) and one old variety (Valtický) of spring barley (Hordeum vulgareL.), the stress responses caused by soil drought were studied. The plants were cultivated at 70 % θMKK. The stress was brought about by interrupting irrigation at the beginning of shooting (31.DC) and by gradual drying-up of the substrate for a period of 10 days down to 30 % θMKK. At selected ontogenetic stages (13.DC, 15.DC, 21.DC, 31.DC, 33.DC, 39.DC, 51.DC and 61.DC) relative water content (RWC) and the gas exchange parameters (gs, A and E) were measured, and these data were used to calculate the water use efficiency (WUE). It was found out that WUE can be used to evaluate the drought-resistance of varieties of spring barley. Although with respect to RWC > 80 %, only a mild stress occurred, the examined genotypes manifested contrast responses to the decrement of water in the substrate with respect to WUE. It can be said that the Malz variety can manage water well and has low sensitivity; the Valtický variety can manage water relatively well and is moderately sensitive, while the Jersey variety is characterised by inferior water management and increased sensitivity to lack of water.