Sucrose Concentration at the Apoplastic Interface between Seed Coat and Cotyledons of Developing Soybean Seeds.

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 approximately 220 milligram fresh weight embryos), implying high diffusion resistance through the tissue.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]  M. Schmitt,et al.  Sugar Transport into Protoplasts Isolated from Developing Soybean Cotyledons : II. Sucrose Transport Kinetics, Selectivity, and Modeling Studies. , 1984, Plant physiology.

[2]  J. Patrick.  Photosynthate Unloading from Seed Coats of Phaseolus vulgaris L. Control by Tissue Water Relations. , 1984, Journal of plant physiology.

[3]  P. Wolswinkel,et al.  Turgor‐sensitive sucrose and amino acid transport into developing seeds of Pisum sativum. Effect of a high sucrose or mannitol concentration in experiments with empty ovules , 1984 .

[4]  R. M. Spanswick,et al.  Concentrations of sucrose and nitrogenous compounds in the apoplast of developing soybean seed coats and embryos. , 1984, Plant Physiology.

[5]  R. Gifford,et al.  Accumulation and Conversion of Sugars by Developing Wheat Grains V. THE ENDOSPERM APOPLAST AND APOPLASTIC TRANSPORT , 1984 .

[6]  J. Patrick.  Photosynthate Unloading From Seed Coats of Phaseolus vulgaris L. General Characteristics and Facilitated Transfer , 1983 .

[7]  R. M. Spanswick,et al.  Derepression of amino Acid-h cotransport in developing soybean embryos. , 1983, Plant physiology.

[8]  J. H. Thorne,et al.  An in vivo technique for the study of Phloem unloading in seed coats of developing soybean seeds. , 1983, Plant physiology.

[9]  J. H. Thorne.  Characterization of the active sucrose transport system of immature soybean embryos. , 1982, Plant physiology.

[10]  R. M. Spanswick,et al.  Sucrose uptake by developing soybean cotyledons. , 1981, Plant physiology.

[11]  K. Zierler,et al.  A critique of compartmental analysis. , 1981, Annual review of biophysics and bioengineering.

[12]  J. H. Thorne.  Morphology and ultrastructure of maternal seed tissues of soybean in relation to the import of photosynthate. , 1981, Plant physiology.

[13]  A. ALLSOPP,et al.  Plant Anatomy , 1966, Nature.