Inhibition of Loading of 14C Assimilates by p-Chloromercuribenzenesulfonic Acid : Localization of the Apoplastic Pathway in Vicia faba

摘要: 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 ability tissues to take up sugars tested. An infiltration time 75 minutes sufficient obtain a maximal (75%) inhibition exogenous [14C]sucrose (1 millimolar) uptake. This affected neither CO2 assimilation nor transmembrane potential difference leaf cells but strongly inhibited phloem loading endogenous [14C] assimilates. study symplastic relations between different cell types showed that density plasmodesmata is generally very low in comparison other species investigated so far, particularly when considering mesophyll/bundle sheath bundle sheath/phloem connections, as well connections transfer cell-sieve tube complex surrounding cells. These three successive barriers therefore limit possibilities transit assimilates conducting densities an importing exporting suggests maturation characterized by marked isolation phloem, and, within itself, complex. As consequence, these physiological cytological data demonstrate apoplastic nature Vicia faba, this undoubtedly presenting typical model for loading.