Inhibition of loading of sup 14 C assimilate by p-chloromercuribenzenesulfonic acid. [Vicia faba L]
- Centre National de la Recherche Scientifique, Poitiers (France)
The apoplast of mature leaves excised from broadbean (Vicia faba L.) plants was infiltrated with 2 millimolar p-chloromercuribenzenesulfonic acid (PCMBS) via the transpiration stream, and the ability of the tissues to take up sugars was tested. An infiltration time of 75 minutes was sufficient of obtain a maximal (75%) inhibition of exogenous ({sup 14}C)sucrose (1 millimolar) uptake. This infiltration affected neither CO{sub 2} assimilation nor the transmembrane potential difference of leaf cells but strongly inhibited phloem loading of endogenous ({sup 14}C) assimilates. The study of the symplastic relations between the different cell types of the mature leaf showed that the density of the plasmodesmata is generally very low in comparison with other species investigated so far, particularly when considering the mesophyll/bundle sheath and the bundle sheath/phloem cells connections, as well as the connections of the transfer cell-sieve tube complex with the surrounding cells. These three successive barriers therefore strongly limit the possibilities of symplastic transit of the assimilates to the conducting cells. The comparison of the densities of plasmodesmata in an importing and an exporting leaf suggests that the maturation of the leaf is characterized by a marked symplastic isolation of the phloem, and, within the phloem itself, by the isolation of the conducting complex. As a consequence, these physiological and cytological data demonstrate the apoplastic nature of loading in the mature leaf of Vicia faba, this species undoubtedly presenting a typical model for apoplastic loading.
- OSTI ID:
- 7007912
- Journal Information:
- Plant Physiology; (USA), Vol. 92:1; ISSN 0032-0889
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
MERCURY COMPLEXES
BIOLOGICAL EFFECTS
VICIA
PHYSIOLOGY
BIOLOGICAL PATHWAYS
CARBON 14 COMPOUNDS
INHIBITION
LEAVES
PLANT TISSUES
TRACER TECHNIQUES
BODY
COMPLEXES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEGUMINOSAE
MAGNOLIOPHYTA
MAGNOLIOPSIDA
PLANTS
TISSUES
551001* - Physiological Systems- Tracer Techniques