PROTECTION OF MEMBRANE INTEGRITY IN MEDICAGO-SATIVA L BY GLYCINEBETAINE AGAINST THE EFFECTS OF FREEZING

To investigate the possibility that glycinebetaine might act as a cryoprotectant, Medicago sativa L. cv. Hunter River seedlings were sprayed with 0.2 M glycinebetaine to run-off. The glycinebetaine was detectable in both shoots and roots following treatment. When plants were subjected to sub-freezing temperatures, glycinebetaine reduced the loss of ions from the shoot tissues, as measured by the electrical conductivity of the bathing solution. This was particularly apparent at -6-degrees-C, which correlated with tissue survival as 67 % of crowns survived one hour at -6-degrees-C if treated with glycinebetaine whereas no control crowns survived such treatment.