Abstract
ABA is known to have an important role in the water stress response. In this study, we investigated the site(s) of ABA synthesis and the ABA movement using wild type and aao3 mutant of Arabidopsis thaliana. In the wild type plants, ABA levels were rapidly increased both in leaves and roots after drought treatment. In contrast, no significant increase was observed in aao3 plants. When wild type plants divided to leaf and root parts were independently exposed to drought, increase of ABA levels was detected in leaf parts, but not in roots. Furthermore, when 13C-ABA was supplied to leaves of aao3 plants, 13C-ABA was detected from the roots after within 60 hr. These results indicate that ABA biosynthesis takes place mainly in leaves in response to drought stress and the accumulated leaf ABA is immediately transported to roots.
