Title

Role of Free Space in Translocation in Sugar Beet

Document Type

Article

Publication Date

12-1-1974

Publication Source

Plant Physiology

Abstract

The involvement of the free space in phloem loading of sucrose was studied in sugar beet source leaves (Beta vulgaris, L.). Sucrose, supplied exogenously to the abraded upper surface of leaves at a concentration of 20 mM, was available for translocation at rates similar to those obtained with photosynthesis. The exogenous sucrose substituted as a source of translocate for assimilate derived from photosynthesis when the latter process was disrupted by plasmolysis of the leaf with 0.8 M mannitol. The mesophyll symplast was not completely disrupted by this treatment, however. Data from the sugar uptake experiments indicate that phloem loading can occur from the free space. Isotope trapping of labeled sugars derived from 14CO2 was used to intercept and identify sugars passing through the free space prior to phloem loading. Increased translocation rates induced by 4 mM ATP or increased light intensity were accompanied by increased trapping of sucrose but not of glucose. The data support the view that sucrose passes into the free space prior to phloem loading.

Inclusive pages

892-898

ISBN/ISSN

0032-0889

Publisher

American Society of Plant Biologists

Volume

54

Peer Reviewed

yes