Evidence for Active Phloem Loading in the Minor Veins of Sugar Beet
- 1 December 1974
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 54 (6), 886-891
- https://doi.org/10.1104/pp.54.6.886
Abstract
Phloem loading in source leaves of sugar beet (Beta vulgaris, L.) was studied to determine the extent of dependence on energy metabolism and the involvement of a carrier system. Dinitrophenol at a concentration of 4 mm uncoupled respiration, lowered source leaf ATP to approximately 40% of the level in the control leaf and inhibited translocation of exogenously supplied 14C-sucrose to approximately 20% of the control. Dinitrophenol at a concentration of 8 mm inhibited rather than promoted CO2 production, indicating a mechanism of inhibition other than uncoupling of respiration. The 8 mm dinitrophenol also reduced ATP to approximately 40% of the level in the control source leaf and reduced translocation of exogenous sucrose to approximately 10% of the control. Application of 4 mm ATP to an untreated source leaf promoted the translocation rate by approximately 80% over the control, while in leaves treated with 4 mm dinitrophenol, 4 mm ATP restored translocation to the control level. No recovery of translocation was observed when ATP was applied to leaves treated with 8 mm dinitrophenol. The results indicate an energy-requiring process for both phloem loading and translocation in the source leaf.Keywords
This publication has 12 references indexed in Scilit:
- Structural and Physiological Changes in Sugar Beet Leaves during Sink to Source ConversionPlant Physiology, 1974
- Vein Loading: The Role of the Symplast in Intercellular Transport of Carbohydrate between the Mesophyll and Minor Veins of Tobacco LeavesPlant Physiology, 1974
- Solute Distribution in Sugar Beet Leaves in Relation to Phloem Loading and TranslocationPlant Physiology, 1973
- Reduction of Water Permeability in Potato Tuber Slices by Cyanide, Ammonia, 2,4-Dinitrophenol, and Oligomycin and Its Reverse by Adenosine 5′-Triphosphate and Cytidine 5′-TriphosphatePlant Physiology, 1973
- Multiphasic Absorption of Glucose and 3-O-Methyl Glucose by Aged Potato SlicesPlant Physiology, 1973
- Leaf Structure and Translocation in Sugar BeetPlant Physiology, 1969
- Comparison of Upward and Downward Translocation of 14C From a Single Leaf of SunflowerPlant Physiology, 1968
- Sugar Uptake and Translocation in the Castor Bean Seedling I. Characteristics of Transfer in Intact and Excised SeedlingsPlant Physiology, 1967
- Evaluation of Selected Parameters in a Sugar Beet Translocation SystemPlant Physiology, 1965
- Sucrose Translocation in the Sugar BeetPlant Physiology, 1965