Comparative response of δ13C, δ18O and δ15N in durum wheat exposed to salinity at the vegetative and reproductive stages.

This study compared the performance of the stable isotope composition of carbon (δ(13) C), oxygen (δ(18) O) and nitrogen (δ(15) N) by tracking plant response and genotypic variability of durum wheat to different salinity conditions. To that end, δ(13) C, δ(18) O and δ(15) N were analysed in dry matter (dm) and the water-soluble fraction (wsf) of leaves from plants exposed to salinity, either soon after plant emergence or at anthesis. The δ(13) C and δ(18) O of the wsf recorded the recent growing conditions, including changes in evaporative conditions. Regardless of the plant part (dm or wsf), δ(13) C and δ(18) O increased and δ(15) N decreased in response to stress. When the stress conditions were established just after emergence, δ(15) N and δ(13) C correlated positively with genotypic differences in biomass, whereas δ(18) O correlated negatively in the most severe treatment. When the stress conditions were imposed at anthesis, relationships between the three isotope signatures and biomass were only significant and positive within the most severe treatments. The results show that nitrogen metabolism, together with stomatal limitation, is involved in the genotypic response to salinity, with the relative importance of each factor depending on the severity and duration of the stress as well as the phenological stage that the stress occurs.