Advances in Botanical Research 2: 125-155 (1985)
Cell Wall Storage Carbohydrates in Seeds—Biochemistry of the Seed “Gums” and “Hemicelluloses”
J. S. Grand Reid

I. INTRODUCTION

By the late nineteenth century it was clearly recognized by botanists that the massively thickened cell walls present in many seeds contained reserve substances. Reiss (1889) and others described “reserve celluloses” which were utilized following germination, while Tschirch (1889) and Nadelmann (1890) were able to demonstrate that the “mucilages” in the endosperm cell walls of some leguminous seeds had a storage function. Schleiden (quoted by Vogel and Schleiden, 1839) reported that the thickened cell walls of some seeds could be stained blue with iodine, and he named the substance responsible for the starchlike reaction “amyloid.” Amyloids were later shown to occur widely in seeds (Winterstein, 1893; Kooiman, 1960a) and to be mobilized following germination (Godfrin, 1884). The carbohydrate nature of the cell wall reserves of seeds was inferred from their microchemical staining reactions, and proven by the positive identification of sugars released from them on acid hydrolysis. For example, the reserve cellulose of the ivory “nut,” Phytelephas macrocarpa, released “seminose” or mannose (Reiss, 1889); the mucilage of the locust “bean,” Ceratonia siliqua, gave mannose and galactose (Bourquelot and Herissey, 1899), and the amyloid of the nasturtium seed, Tropaeolum majus, yielded glucose, xylose, and galactose (Winterstein, 1893). The combined ultrastructural, physiological, and “biochemical” approach which many of the early botanists adopted to study the cell wall storage carbohydrates of seeds was extraordinarily effective. It is unfortunate that it was not carried forward with vigor into the twentieth century.

The mid-twentieth century (1930-1970) saw the introduction of a series of new techniques for the determination of the structures of complex carbohydrates (Whistler and Wolfrom, 1965; Whistler and Bemiller, 1972) and most of our present knowledge of the structures of cell wall storage carbohydrates was obtained during that period. Seeds were generally treated with alkali to extract polysaccharides of the “hemicellulose” type or with water to extract “gum” polysaccharides. Consequently the molecules with which this article is concerned are still widely classified as seed gums and hemicelluloses.

In recent years (from about 1970) there has been a reawakening of interest in the physiology and biochemistry of the cell wall storage carbohydrates of seeds, and a recent review article has treated them for the first time as a single, botanically coherent group of substances (Meier and Reid, 1982). It is the purpose of this article to outline the structures and occurrence of cell wall storage carbohydrates, to give an account of current research on their metabolism, and to explore their overall biological significance in the seeds which contain them.