Barley yield in water-stress conditions. The influence of precocity, osmotic adjustment and stomatal conductance

The behavior of eight cultivated barley (Hordeum vulgare L.) genotypes cons isting of three breeding lines and five cultivars varieties was studied in a rain shelter to determine the influence of osmotic adjustment and stomata l conductance on drought tolerance and yield under terminal water stress. W hen the crop reached the flag leaf stage, half of the experimental plots we re submitted to a water-stress treatment and the remainder maintained in op timal water conditions. Variation was observed in osmotic adjustment (OA) a nd stomatal conductance among the genotypes under stress. Two of the breedi ng lines exhibited the highest OA capacity. These lines also showed the lea st differences in stomatal conductance and maintained the highest stomatal conductance as water stress increased. Correlations between yield and OA an d conductance in the water-stress treatment were positive and significant. In the irrigated control the correlation coefficients were smaller. Osmotic adjustment and stomatal conductance were linearly related, indicating that OA favors higher conductance when there is water stress. Under conditions of terminal drought yield was negatively correlated with time to ear emerge nce and maturity. Earliness to flower and OA contributed to greater yields under terminal water stress. (C) 1999 Elsevier Science B.V All rights reser ved.