Adaptation to high salinity in poplar involves changes in xylem anatomy and auxin physiology.

Junghans, U.; Polle, A.; Düchting, P.; Weiler, E.; Kuhlman, B.; Gruber, F.; Teichmann, T.

To investigate the physiological basis of salt adaptation in poplar, we compared the effect of salt stress on wood anatomy and auxin physiology of the salt-resistant Populus euphratica and salt-sensitive Populus × canescens. Both poplar species showed decreases in vessel lumina associated with increases in wall strength in response to salt, however, in P. euphratica at three-fold higher salt concentrations than in P. × canescens. The predicted hydraulic conductivity of the wood formed under salt stress decreased in P. × canescens, while in P. euphratica, no significant effects of salt on conductivity and transpiration were observed. The concentration of free indole-3-acetic acid (IAA) decreased under salt stress in the xylem of both poplar species, but to a larger extent in P. × canescens than in P. euphratica. Only salt-treated P. euphratica exhibited an increase in IAA-conjugates in the xylem. Genes homologous to the auxin-amidohydrolase ILL3 were isolated from the xylems of P. euphratica and P. × canescens. For functional analysis, the auxin-amidohydrolase from P. × canescens was overexpressed in Arabidopsis. Transgenic Arabidopsis plants were more resistant to salt stress than the wild-type plants. Increased sensitivity of the transgenic Arabidopsis to IAA-Leu showed that the encoded hydrolase used IAA-Leu as a substrate. These results suggest that poplar can use IAA-amidoconjugates in the stem as a source of auxin to balance the effects of salt stress on auxin physiology.

POPLARS; XYLEM; VASCULAR system of plants; PLANT cells & tissues; AUXIN; PLANT hormones; PLANT anatomy; SALICACEAE; ARABIDOPSIS

Plant, Cell & Environment, 2006, Vol 29, Issue 8, p1519

0140-7791

Academic Journal

10.1111/j.1365-3040.2006.01529.x