Inhibition of loading of sup 14 C assimilate by p-chloromercuribenzenesulfonic acid. [Vicia faba L]

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Plant Physiology; (USA)

DOI:https://doi.org/10.1104/pp.92.1.97· OSTI ID:7007912

Bourquin, S; Bonnemain, J L; Delrot, S ^[1]

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1. 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), Journal Name: Plant Physiology; (USA) Vol. 92:1; ISSN 0032-0889; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BIOLOGICAL EFFECTS
BIOLOGICAL PATHWAYS
BODY
CARBON 14 COMPOUNDS
COMPLEXES
INHIBITION
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEAVES
LEGUMINOSAE
MAGNOLIOPHYTA
MAGNOLIOPSIDA
MERCURY COMPLEXES
PHYSIOLOGY
PLANT TISSUES
PLANTS
TISSUES
TRACER TECHNIQUES
VICIA