Phloem loading: an integrated approach

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:5239526

Wilson, C

This study focuses on the regulation of sucrose transport across the plasmalemma. Initially, we re-examined the use of leaf discs to study the kinetics of phloem loading using Allium cepa leaves. All tissues exhibited the same linear plus saturable profile as Beta vulgaris, except fructose uptake into the inner parenchyma and bundle-sheath cells; in this case the response was linear. These results indicate that all tissues of the leaf retrieve exogenous sucrose such that kinetics from leaf discs cannot be taken to represent phloem loading per se. We continued our study by investigating the influence of internal sugars on sugar transport across the plasmalemma. We found that if internal sugars were manipulated by heat-girdling techniques or DCMU treatment there was no appreciable change in sucrose influx. However, longer term heat-girdling decreased sucrose uptake. These data indicate that carbohydrate partitioning among the chloroplast, cytosol, and vacuole modulates cytosolic sugar levels. One interesting discovery was that leaves excised from the plant and allowed to undergo their normal day/night cycle do not transfer (/sup 14/C) sucrose to their minor veins.

• Research Organization: California Univ., Davis (USA)
• OSTI ID: 5239526
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BEETS
BODY
CARBOHYDRATES
CARBON 14 COMPOUNDS
CELL CONSTITUENTS
CELL MEMBRANES
DISACCHARIDES
ENERGY
FOOD
HEAT
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEAVES
MEMBRANE TRANSPORT
MEMBRANES
OLIGOSACCHARIDES
ONIONS
ORGANIC COMPOUNDS
PERMEABILITY
PLANT TISSUES
PLANTS
SACCHARIDES
SACCHAROSE
TISSUES
TRACER TECHNIQUES
VEGETABLES