An Enzymic Method for Measuring the Molecular Weight Exclusion Limit of Plasmodesmata of Bundle Sheath Cells of C4 Plants

Bundle sheath cell strands have been prepared from four C₄ plantspecies and used to study the molecular weight exclusion limitof plasmodesmata located in the cell wall of bundle sheath cells.By measuring the activity and the inhibition of enzymes locatedwithin the bundle sheath cells of the strands in the absenceor presence of a variety of inhibitors of different molecularweight, the molecular weight exclusion limit of the plasmodesmatalocated within the cell walls of bundle sheath cells has beendetermined. Using a variety of Reactive dyes (of different molecularweight) which inhibit a number of cytosohc enzymes, as wellas a graded series of Reactive Yellow 2 derivatives as probes,it has been shown that compounds with molecular weights greaterthan about 900 daltons do not pass through the plasmodesmataof bundle sheath cells of C₄ plants. Key words: Plasmodesmata, molecular weight exclusion limit, bundle sheath cells