Using stable isotope natural abundances (delta N-15 and delta C-13) to integrate the stress responses of wild barley (Hordeum spontaneum C. Koch.) genotypes

To integrate the complex physiological responses of plants to stress, natur al abundances (delta) of the stable isotope pairs N-15/N-14 and C-13/C-12 w ere measured in 30 genotypes of wild barley (Hordeum spontaneum C, Koch,), These accessions, originating from ecologically diverse sites, were grown i n a controlled environment and subjected to mild, short-term drought or N-s tarvation, Increases in total dry weight were paralleled by less negative d elta(13)C in shoots and, in unstressed and droughted plants, by less negati ve whole-plant delta(13)C. Root delta(15)N was correlated negatively with t otal dry weight, whereas shoot and whole-plant delta(15)N were not correlat ed with dry weight. The difference in delta(15)N between shoot and root var ied with stress in all genotypes, Shoot-root delta(15)N may be a more sensi tive indicator of stress response than shoot, root or whole-plant delta(15) N alone. Among the potentially most productive genotypes, the most stress-t olerant had the most negative whole-plant delta(15)N, whether the stress wa s drought or N-starvation. In common, controlled experiments, genotypic dif ferences in whole-plant delta(15)N may reflect the extent to which N can be retained within plants when stressed.