The effect of a water stress on the cold hardiness of winter wheat

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Abstract
Crowns of winter wheat plants water stressed with polyethylene glycol (PEG) (molecular weight 20 000) prior to hardening were more cold hardy than tender crowns or crowns hardened for 2 days (p ≤ 0.05). After 16 days of hardening, plants from all treatments reached the same level of hardiness. Winter wheat crowns water stressed with PEG (210 g/L) for either 0,5, or 21 days reached the same level of hardiness after 2 days of acclimation. In both short- and long-term stress studies, the crown moisture content of the stressed plants was lower (p ≤ 0.05) than that of the controls prior to acclimation. With increasing hardiness both leaf osmotic potential and crown moisture content decreased (p ≤ 0.05). Short-term water stress also resulted in an increase in sugars, specifically sucrose (p ≤ 0.05) prior to cold hardening. However the total sugar content did not parallel the increase in hardiness.Changes in several metabolic parameters were also considered. Significant correlations were found in both studies between the LT50 and osmotic potential, moisture content, and dry weight. Most of the variability in LT50 could be explained by changes in leaf osmotic potential and crown moisture content.