The Role of the Endosperm in the Germination of Legumes: Galactomannan, Nitrogen, and Phosphorus Changes in the Germination of Guar (Cyamopsis tetragonoloba; Leguminosae)

Abstract

The endosperm of Cyamopsis tetragonoloba (“guar”) contains 41 % of the dry weight and 45 % of the acetone-insoluble-solids of the seed, but only 3–11 % of the nitrogen and phosphorus. At least 75 % of the acetone-insoluble-solids of the endosperm is galactomannan, only about 12% being accounted for as pentosan, pectin, protein, phytin, ash, and dilute-acid-insoluble residue. During a five-day germination period at 30 C, all of the galactomannan and all but 5 % of the dry weight of the endosperm disappeared, being translocated to the cotyledons. About ⅓ of the nitrogen and phosphorus of the endosperm plus seed coat were also translocated. After a 36-hr lag, the accumulation of the nitrogen and acetone-insoluble-solids in the seedling axis were linear, while the total dry weight and phosphorus showed a rapid increase followed by a slower accumulation during the five-day period. In the cotyledons, the dry weight temporarily increased, but the acetone-insoluble-solids, nitrogen and phosphorus showed only a net decrease after 84, 36 and 36 hr, respectively. Scanning election micrographs of dry-fractured and sectioned endosperm show that the bulk of the endosperm is a solid mass of galactomannan with essentially no cell lumina; a several-cell layer (“aleurone”) of thick-walled cells of similar structure is metabolically active.