ABSTRACT
Summary Effects of a freezing-waterlogging-freezing treatment, under controlled environmental conditions, on the viability and chemical components of alfalfa (Medicago sativa L.) were determined to assess physiological responses to midwinter thaw. Alfalfa plants grown in a field were more resistant to freezing but less resistant to waterlogging than those grown in a greenhouse. Both types of plants sustained severe damage from the second freezing treatment. An accumulation of ethanol and methanol, a solubilization of proteins, and a decrease in carbohydrates occurred during the waterlogging. Two important physiological characteristics for surviving a midwinter thaw appear to be an ability to maintain freezing resistance during the thawing period and an ability to remove ethanol quickly after waterlogging.
