Pathway of phloem unloading in tobacco sink leaves. [Nicotiana tabacum]

Conference · Wed Apr 01 04:00:00 EST 1987 · Plant Physiol., Suppl.; (United States)

OSTI ID:6070830

Turgeon, R

Phloem unloading in transition sink leaves of tobacco (Nicotiana tabacum L.) was analyzed by quantitative autoradiography. Source leaves were labeled with /sup 14/CO/sub 2/ and experimental treatments were begun approximately 1 h later when label had entered the sink leaves. Autoradiographs were prepared from rapidly frozen, lyophilized sink tissue at the beginning and end of the treatments and the amount of label in veins and in surrounding cells was determined by microdensitometry. Photoassimilate unloaded from third order and larger, but not smaller, veins. Long-distance import and unloading did not respond the same way to all experimental treatments. Import was completely inhibited by cold, anaerobiosis or steam girdling the sink leaf petiole. Unloading was inhibited by cold but continued in an anaerobic atmosphere and after steam girdling. Uptake of exogenous (/sup 14/C)sucrose was inhibited by anaerobiosis. Since an apoplastic pathway of phloem unloading would involve solute uptake from the apoplast the results are most consistent with passive symplastic unloading of photoassimilates from phloem to surrounding cells.

• Research Organization: Cornell Univ., Ithaca, NY
• OSTI ID: 6070830
• Report Number(s): CONF-8707108-
• Conference Information: Journal Name: Plant Physiol., Suppl.; (United States) Journal Volume: 83:4
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
560200 -- Thermal Effects
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANAEROBIC CONDITIONS
AUTORADIOGRAPHY
BIOLOGICAL EFFECTS
BIOLOGICAL PATHWAYS
CARBOHYDRATES
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
DISACCHARIDES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEAVES
NICOTIANA
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANT STEMS
PLANTS
SACCHARIDES
SACCHAROSE
SOLUTES
SYNTHESIS
TEMPERATURE EFFECTS
TRACER TECHNIQUES
TRANSLOCATION
UPTAKE