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

During a 5 degree C and a 5/-1 degree 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 degree C CA plants. Results of carbohydrate analysis illustrated a significant (P < 0.001) accumulation of sucrose, fructose and glucose in the 5/-1 degree 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 degree 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 degree 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 degree C, where non-cold acclimated plants produced 2.3 +/- 0.3 tillers and 5 degree C and 5/-1 degree C CA plants produced 2.4 +/- 0.3 and 4.7 +/- 0.7 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.