The effect of cold-acclimation on the water relations and freezing tolerance of Hordeum vulgare L.

During a 5°C and a 5/-1°C cold acclimation (CA) regime there was a significant decline in the water potential of winter barley, and a concurrent decline in tissue water content of the 5/-1°C CA plants. Results of carbohydrate analysis illustrated a significant (P<0.001) accumulation of sucrose, fructose and glucose in the 5/−1°C CA plants, which was inversely correlated to water potential. Using an infrared imaging radiometer during a convection frost test the water release time (WRT) of 5/−1°C CA was demonstrated to be significantly (P<0.001) longer than that observed in non-cold acclimated plants. This observation is consistent with visual analysis of exotherm curves where the rate of cellular water release to extracellular ice is reduced in the 5/−1°C CA plants, compared to the non-cold acclimated plants. These biochemical and physiological changes were correlated to increased plant health following a non-lethal freezing test to −5°C, where non-cold acclimated plants produced 2.3 ± 0.33 tillers and 5°C and 5/−1°C A plants produced 2.4 ± 0.33 and 4.7 ± 0.67 tillers, respectively. Results from this study imply that cold acclimation leads to changes in the physical state of water that result in a less osmotically responsive cellular environment and subsequently significantly less damage to meristematic tissue.