Transport and action of ascorbate at the plant plasma membrane

The plasmalemma is both a bridge and a barrier between the cytoplasm and th e outside world. It is a dynamic interface that perceives and transmits inf ormation concerning changes in the environment to the nucleus to modify gen e expression. In plants, ascorbate is an essential part of this dialogue. T he concentration and ratio of reduced to oxidized ascorbate in the apoplast , for example, possibly modulates cell division and growth. The leaf apopla st contains millimolar amounts of ascorbate that protect the plasmalemma ag ainst oxidative damage. The apoplastic ascorbate-dehydroascorbate redox cou ple is linked to the cytoplasmic ascorbate-dehydroascorbate redox couple by specific transporters for either or both metabolites. Although evidence ab out the mechanisms driving ascorbate or dehydroascorbate transport remains inconclusive, these carrier proteins potentially regulate the level and red ox status of ascorbate in the apoplast. The redox coupling between compartm ents facilitated by these transport systems allows coordinated control of k ey physiological responses to environmental cues.