Phloem unloading in developing leaves of sugar beet
Physiological and transport data support a symplastic pathway for phloem unloading in developing leaves of sugar beet (Beta vulgaris L. Klein E, multigerm). The sulfhydryl inhibitor parachloromercuribenzene sulfonic acid (PCMBS) inhibited uptake of (/sup 14/C)-sucrose added to the free space of developing leaves, but did not affect import of (/sup 14/C)-sucrose during steady-state /sup 14/CO/sub 2/ labeling of a source leaf. The passively-transported xenobiotic sugar, (/sup 14/C)-L-glucose did not readily enter mesophyll cells when supplied through the cut end of the petiole of a sink leaf as determined by whole leaf autoradiography. In contrast, (/sup 14/C)-L-glucose translocated through the phloem from a mature leaf, rapidly entered mesophyll cells, and was evenly distributed between mesophyll and veins. Autoradiographs of developing leaves following a pulse of /sup 14/CO/sub 2/ to a source leaf revealed rapid passage of phloem translocated into progressively higher order veins as the leaf developed. Entry into V order veins occurred during the last stage of import through the phloem. Import into developing leaves was inhibited by glyphosate (N-phosphomethylglycine), a herbicide which inhibits the aromatic amino acid pathway and hence protein synthesis. Glyphosate also stopped net starch accumulation in sprayed mature leaves, but did not affect export of carbon from treated leaves during the time period that import into developed leaves was inhibited.
- Research Organization:
- Dayton Univ., OH (USA)
- OSTI ID:
- 5940109
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LEAVES
AUTORADIOGRAPHY
SUGAR BEETS
PHYSIOLOGY
BIOLOGICAL PATHWAYS
CARBON 14 COMPOUNDS
CARBON DIOXIDE
GLUCOSE
INHIBITION
SACCHAROSE
THIOLS
TRACER TECHNIQUES
UPTAKE
ALDEHYDES
BEETS
CARBOHYDRATES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
DISACCHARIDES
FOOD
HEXOSES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MONOSACCHARIDES
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLANTS
SACCHARIDES
VEGETABLES
551001* - Physiological Systems- Tracer Techniques