A comparison of glycolytic activity in winter wheat and two forage grasses in relation to their tolerance to ice encasement

Melting and refreezing within snow layers can cause the build-up of ice at soil surfaces, which can severely damage overwintering crop plants. The relatively limited tolerance of cold acclimated winter wheat to ice encasement is increased by a prior exposure to low temperature flooding. This is a hypoxic acclimation. In wheat, it is accompanied by a three-fold increase in the activity of pyruvate decarboxylase (PDC) and a two-fold increase in the activity of alcohol dehydrogenase (ADH). Activity of PDC is one tenth that of ADH. The glycolytic kinases [ATP-phosphofructokinase (PFK), PPi-phosphofructophosphotransferase (PFP), and pyruvate kinase (PK)] show little change during the acclimation process. The forage grasses timothy (Phleum pratense) and berings hairgrass (Deschampsia berengensis) when cold acclimated, are more tolerant to ice encasement than winter wheat, and show a relatively small hypoxic acclimation response. During ice encasement, these forage grasses accumulate less ethanol, CO2 and lactic acid than wheat. In further contrast to wheat, they produce lower levels of these metabolites in ice following acclimative flooding than they do in the absence of flooding. Activity of DC and ADH in crowns of the two forage grasses is also less than in wheat. These observations indicate that high ice encasement tolerance of the grasses may be associated with slow fermentation rates and low accumulation of toxic metabolites. (C) 1997 Annals of Botany Company