Accumulation of glycinebetaine during cold acclimation and freezing tolerance in leaves of winter and spring barley plants

Abstract

ABSTRACTA study was performed to examine whether or not betaine (glycinebetaine), a compatible solute, is accumulated in response to cold stress and is involved in mechanisms that protect plants from freezing injury. For this purpose, we used near‐isogenic lines of barley, with each line differing only in a single gene for the spring type of growth habit; the various lines were produced by back‐crosses to a recurrent cultivar of the winter type. The winter type of growth habit requires a low temperature for triggering of flower development (vernalization), whereas the spring type does not. Betaine was accumulated to five times the basal level over the course of 3 weeks at low temperature (5 °C) in the winter‐type cultivar and in a spring‐sh line having the sh gene for the spring‐type growth habit, but the level was only doubled in the spring‐Sh3 line, which carried the Sh3 gene for the spring‐type growth habit. Among near‐isogenic lines of the same cultivar, the levels of betaine accumulated in leaves at low temperature were well correlated with the percentages (on a dry weight basis) of green leaves that survived freezing injury (‐5 °C). This observation indicates the possibility, separate from the recognized role of betaine in the response to salinity and/or drought, that betaine accumulates in response to cold stress and that the accumulation of betaine during cold acclimation is associated to some extent with freezing tolerance in leaves of barley plants.