We investigated the controls of ABA concentration in the xylem sap and of stomatal conductance in five barley (Hordeum vulgare L.) lines of contrasting origins (Syrian or French), genetic backgrounds and previously field-evaluated drought resistances. Controlled water deficits were applied to young plants in a series of experiments in the greenhouse with contrasting evaporative demands. There was a unique relationship between soil water status and the concentration of ABA in the xylem sap measured at the end of the night. This relationship applied to all experiments for a given line, and was common between lines. Concentrations measured in the sap collected by pressurising leaves were similar to those in the sap of pressurised roots. Stomatal conductance was related to the concentration of ABA in the sap, with relationships which were common for all experiments within each line. Response curves of g s to concentration of ABA in the sap differed among two groups of lines which slightly differed in life cycle duration. Apparent stomatal sensitivity to ABA was lower in earliest anthesing lines. Both groups comprised lines of either Syrian or French origins, and either Ôdrought tolerantÕ or Ôdrought susceptibleÕ lines. We conclude that stomatal control had a low genetic variability in the studied range of lines, in spite of the large genetic differences between lines.
This simultaneous combined-modality regimen was feasible at the cost of severe mucosal toxicity, which required hospitalization with nutritional, parenteral, and hydroelectrolytic support. The high response rate achieved (70%) did not translate into improved survival, probably due to patient eligibility. The likelihood of cure of this high-tumoral-volume patient population remains low (approximately 10%), despite the association of two therapeutic modalities at full standard therapeutic intensity.
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