Root Growth and Carbohydrate Metabolism at Low Temperatures

A study of carbohydrate metabolism in the roots of pea and maizeshows that the differing ability of these two species to growat low temperatures is associated with the maintenance of adequatesugar supplies to the root tip. In the maize root reducing theambient temperature to 2 °C causes a sharp and continuingfall in the soluble sugar content of the growing tip. A similartreatment with pea roots causes only a temporary reduction insugar content lasting no more than 24 h. The fall in root sugarsin maize is accompanied by a reduction in respiration rate andthe cessation of growth. During the periods of sugar shortagecaused by low temperatures both respiration and growth can bestimulated in root tips by a supply of exogenous glucose. Pearoots also show an additional ability to adapt to low temperaturesby lowering the K^m value for invertase after pretreatment ata low temperature. This effect is not seen in maize.