Yuriko Osakabe and colleagues from the RIKEN Center for Sustainable Resource
Science have studied several newly identified molecules involved in the
transport of the hormone abscisic acid (ABA) in plants.

Production of ABA is an essential component of plant response to drought and
salinity. Previously thought to be a long-distance messenger of stress,
studies now suggest that ABA is produced in the veins of the leaves
themselves, where it acts on nearby stomata. Specialized 'guard' cells,
which close and open the stomata, are also able to produce ABA. The team
also found that ABA causes the production of reactive oxygen species that
act as 'secondary messengers', regulating the flux of ions, and in turn the
electrical polarization of the cell membrane, turgor pressure, and
guard-cell closure.

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