Levels of Betaine and Betaine Aldehyde Dehydrogenase Activity in the Green Leaves, and Etiolated Leaves and Roots of Barley 1

The accumulation of betaine and the induction of betaine aldehyde dehydrogenase, which catalyzes the last step in the synthesis of betaine, were analyzed in salt-stressed barley leaves. When hydroponically grown barley plants were transferred to a medium that contained 200 mM NaCl, the levels of both betaine and the total extractable betaine aldehyde dehydrogenase activity in the leaves increased approximately 7-fold and 3-fold when calculated on the basis of total leaf protein, respectively, over the course of 7 days. Betaine aldehyde dehydrogenase activity was also detected in either etiolated leaves or roots of barley plants grown under aseptic conditions. Betaine was detected in both etiolated leaves and roots at levels that were about 20% of that in green leaves when calculated on a fresh weight basis.