Cereal crop improvement programmes involve the analysis of a great number of lines every year; the availability of a simple, rapid method that would allow the identification of a trait in the early stages of plant development would facilitate the selection process. This work reports two experiments involving the germination of seeds in Petri dishes, performed to study the effect of water deficit on the growth of barley coleoptiles. In one experiment water stress was induced by allowing

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... on from the Petri dishes; in the other water stress was achieved by adding polyethylene glycol 6000. The growth of the control coleoptiles was greater than that of the treatment coleoptiles in all cases, but with differences between the different genotypes. A significant correlation (P < 0.01) was found between the relative growth of the coleoptiles and turgor maintenance in the seedlings. Significant correlations were also seen between the relative growth of the coleoptiles and the osmotic adjustment of the flag leaf (P < 0.05) and the grain weight (P < 0.01) in adult plants. The genotypes that showed the greatest relative growth also showed the greatest capacity for osmotic adjustment in the flag leaf and produced the greatest yields in experiments with adult plants. The results indicate that the growth of coleoptiles subjected to water deficit could be used as a selection criterion in breeding programmes designed to improve the tolerance of barley to drought.