Fig. 4.

Guard cell walls are rich in pectin and contain arabinan epitopes. (A) Cell walls from epidermal strips were hydrolyzed in trifluoroacetic acid, and the monosaccharides released were analyzed by anion-exchange chromatography. (B–F) Resin-embedded sections (0.5 μm thick) of epidermal strips were probed with monoclonal antibodies that bind arabinans (LM6), esterified HGA (JIM7), or unesterified HGA (JIM5). Labeling was detected with a FITC-labeled secondary antibody and visualized by fluorescence microscopy. The images shown represent LM6 (1:20) (B), control probed with secondary antibody only (C), an unlabeled section viewed under UV light to reveal autofluorescent material corresponding to endogenous wall phenolic compounds (D), JIM7 (1:50) (E), and JIM5 (1:20) (F). E, epidermal cells; S, subsidiary cells; G, guard cells. (Bars = 10 μm.)