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Plant Physiology 77:863-868 (1985) © 1985 American Society of Plant Biologists Sucrose Concentration at the Apoplastic Interface between Seed Coat and Cotyledons of Developing Soybean SeedsCentral Research and Development Department, Experimental Station, E. I. du Pont de Nemours, and Company, Wilmington, Delaware 19801
The apoplastic sucrose concentration at the interface between cotyledons and surrounding seed coats of developing soybeans (Glycine max L. Merr. cv Wye) was found by three indirect methods to be in the range of 150 to 200 millimolar. This is an order of magnitude higher than has been reported elsewhere for soybean. It was also higher than the overall sucrose concentrations in the cotyledons and seed coats, each of which was approximately 90 millimolar. By defoliating plants 24 hours before measurement, both the overall sucrose concentration in the cotyledons and the interfacial apoplastic sucrose concentration were reduced by three-fourths. However, there was no day/night difference in overall tissue sucrose concentration of cotyledons or seed coats from intact plants suggesting the existence of a homeostatic mechanism compensating for the diurnal photosynthetic cycle. About 7 hours were required for a tritiated polyethylene glycol-900 solution to fully permeate developing cotyledons (from These results indicate that a high interfacial sucrose concentration may exist in vivo. They suggest that the saturable carrier-mediated component of sucrose uptake may be of little physiological significance in the outermost cell layers of the cotyledons.
1 Visiting scientist from CSIRO, Australia with support from E. I. du Pont and Company. Present address: Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, GPO Box 1600, Canberra, A.C.T. 2601, Australia. 2 Present address: E. I. du Pont de Nemours and Company, Agricultural Chemicals Department, Stine-Haskell, P.O. Box 30, Newark, DE 19714. This article has been cited by other articles:
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