Determination of transpiration rate and water use efficiency in terms of drought resistance in some barley( Hordeum vulgare L. ) genotypes

Although barley is not used directly in human nutrition, it is a very important culture plant in animal nutrition. However, it is exposed to water stress in the arid and semi-arid areas, and the yield is also significantly reduced by drought. Therefore the development of drought- tolerant barley genotypes is of great importance. Mechanisms regulating plant transpiration and physiological features related to transpiration have been used commonly by researchers in recent drought studies. One of these methods is to preserve the water by reducing the transpiration rate (TR) of the plant in the high vapor pressure deficit (VPD) period, which usually occurs in the middle of the day. Another strategy is that the genotypes maintain soil water through transpiration restriction at a certain FTSW threshold before the drought period begins. This research was carried out as three independent experimental sets in greenhouse and growth chamber in Faculty of Agriculture of Dicle University. Six registered barley varieties and one barley line were used in the study as a plant material. The presence of phenotypic correlation between parameters characterizing the size and TR sensitivity of the genetic variability of sensitivity to TR was investigated under the effect of gradually increasing drought in the VPD and FTSW experiments. In the four genotypes, used in the study, there was a break point with increased VPD, transpiration response ranging from 2.38 - 2.50 kPa, while TR increased linearly with increasing VPD in the other three genotypes. In these genotypes, the transpiration response given to a gradually decreasing fraction of transpirable soil water (FTSW) varies between genotypes with breakpoints ranging from 0.32 to 0.53. The range of the some trait changed from 2.33-4.26 for transpiration efficiency; 29.7 to 37.6 g for biomass produced; 42.46-49.88 for chlorophyll content values; 116.5-138.8 for heading day; 91.3-127.5 cm for plant height; 5.1-11.0 cm for spike length; 21.8-35.4 for the number of grains in the spike ; 0.95-1.80 g for spike yield; 35.6-50.1 g for thousand grain weight. As a result of the research; some genotypes showed superiority over other genotypes. The classification of genotypes according to traits examined is as follows; Kendal for transpiration efficiency and spike yield; Barış for days of heading, biomass production and spike height; Hevsel for chlorophyll content and one thousand grains; Önder for plant height; Altıkat for the number of grain in the spike. Kendal and Hevsel varieties had better resistance to drought than other genotypes according to the results obtained from FTSW and VPD experiments. Key Words: Barley, Drought, Transpiration rate, Transpiration efficiency, VPD, FTSW