Estimating ice encasement tolerance of herbage plants.

One of the key stresses acting on herbage plants during winter is ice encasement, when plants are enclosed in compact ice and turn from aerobic to anaerobic respiration. The cause of cell death is related to the accumulation of metabolites to toxic levels during winter and perhaps also to production of reactive oxygen species (ROS) when plants escape from long-lasting ice cover. The process of ice encasement damage has been studied by sampling studies, indirect measurements of ice tolerance, field tests and provocation methods by increasing stress in the field artificially, thus increasing the ice stress. Here we describe a laboratory method to measure ice encasement tolerance. This is the most common and effective way to measure ice encasement tolerance of large plant material. Plants are raised from seeds (or taken from the field), cold acclimated, usually at +2 °C under short day conditions, in a greenhouse or growth chamber (or in the field during fall). Plants are submerged in cold water in beakers and frozen encased in ice, usually at -2 °C. Plants are kept enclosed in ice at this temperature. Samples are taken at intervals, depending on species and tolerance of plant material, and put smoothly to regrowth. Damage is then evaluated after a suitable time of regeneration.