It was recently shown (l-3) that a major portion of the lipid fraction of green plant tissue consists not of simple fatty acid glycerides but of glycerol esterified with fatty acid and one or more molecules of a monosaccharide that is generally galactose. Although the occurrence of this lipid-bound sugar is now well established and there is good evidence that at least part of it is a product of photosynthesis intimately associated with chloroplasts (2, 4), the part it plays in plant metabolism has not yet been defined. In addition to its possible role in the plant, this sugar fraction is of interest in connection with carbohydrate fermentation in the ruminant, particularly in animals feeding on pasture. In order to investigate fluctuations of the lipid-bound sugar in plants and to assess its possible importance in rumen fermentation a method for its rapid routine measurement in plant tissue is required. The methods used so far for establishing the presence of glycolipids in plants are either too slow or too difficult for routine use or give only an indication of the concentration present. The only available method (5), which does give a quantitative measure of the various galactoglyceride fractions, involves twodimensional quantitative paper chromatography, and would be t.edious if many samples had to be analyzed.
This paper describes a method for measuring the total lipid-bound sugar that should be suitable for routine use and can be fitted into the type of analysis scheme commonly used for measuring the concentrations of other plant carbohydrates. Results obtained in using the method for measuring the concentration of lipid galactose in several pasture plants are included.
MATERIALS AND METHODS
Plant Material
Plant tissue was obtained from the following plant species; perennial rye grass (Lo&cm peren.ne), red clover (Trifolium pratense), and white