ABA accumulation in dehydrating leaves is associated with decline in cell volume not turgor pressure

Desiccating leaves show increased ABA levels triggered by low turgor – right? Apparently not! The pressure chamber experiments showing increased ABA levels in desiccating leaves are inconsistent when the entire leaves are enclosed in the chamber. Sack et al. proposes that the turgor pressure is increased during the pressure chamber treatment, rather than decreased and could therefore not be a trigger for ABA accumulation. New equations allow estimation of relative water content, which corresponds to reduction in cell volume and ABA accumulation. Applying the proposed equations to new high-resolution pressure studies will allow identification of dehydration sensors, based on decline in relative water content, occurring before destructive turgor loss. (Summary by Magdalena Julkowska) Plant Physiol.