WATER‐SOLUBLE CARBOHYDRATES OF SEEDS OF THE GRAMINEAE

Abstract

summaryQualitative and quantitative determinations have been made of the sugars, oligosaccha‐rides and water‐soluble polysaccharides of the seeds of twenty‐two species of the Gramineae.Although in most species sucrose was the most plentiful free sugar, in Lolium perenne and in Festuca pratensis a trisaccharide which contained residues of galactose, glucose and fructose and which was chromatographically distinct from raffinose constituted the most abundant oligosaccharide; in Elymus arenarius and in Bromus sterilis an homologous series of low‐molecular fructosans represented the major simple carbohydrate. Similar fructosans were also present in Agropyron repens.Raffinose was present in fifteen of the seeds examined and stachyose in ten of these fifteen raffinose‐containing seeds. The contents of raffinose and stachyose were positively correlated.Water‐soluble polysaccharides were obtained in yields approaching 1 per cent of the dry weight of the seeds from certain members of the Bromeae, the Hordeeae, the Festuceae and the Aveneae; yields from members of other tribes were low and predominantly dextrinous in nature.A pure β‐glucosan, resembling that of cultivated barley, has been obtained from Bromus, from Avena and Arrhenatherum, and from Dactylis and other members of the Festuceae. The polysaccharide prepared from Nardus contained a high proportion of mannan and that from Molinia a high proportion of galactan.When the water‐soluble carbohydrates of these seeds are considered in relation to the classification of the Gramineae, it is seen that Bromus is quite distinct from Brachy‐podium; that the members of the Festuceae here examined show underlying similarity in the composition of their water‐soluble polysaccharides, though Festuca pratensis and Lolium perenne are distinctive in containing an unusual trisaccharide; that Avena and Arrhenatherum differ from the other two members of the Aveneae examined (Holcus and Anthoxanthum) and that the members of the Hordeae constitute a natural group on the basis of their sugars content.