MODULATED CHLOROPHYLL FLUORESCENCE AND PHOTOSYNTHETIC GAS-EXCHANGE ASRAPID SCREENING METHODS FOR DROUGHT TOLERANCE IN BARLEY GENOTYPES

Determination of modulated chlorophyll fluorescence coupled to measure ments of the net photosynthetic rate (P(N)) and leaf water potential h as been assessed as a screening method to score a set of twenty genoty pes of barley (Hordeum vulgare L.) for drought tolerance. These method s can be used as rapid screening tests for water stress tolerance in b arley, although applied alone they are appropriate indicators for a se vere water stress. For genotypes growing under a mild water stress, it is necessary to use several screening tests simultaneously. Drought t olerant genotypes show smaller variations of photochemical quenching, P(N), water use efficiency and leaf temperature than the drought sensi tive ones.