Method for visualizing the vascular bundles in stem --Cheng, WY, Cheng, PC, Walden, DB A method was developed to visualize the arrangement of vasculatures in the absence of the parenchyma cells. To visualize the vasculature, mature stems were placed in cellulase-pectinase solution to remove parenchyma cells. (Cellulase from T. longibrachiatum; Cat. WA18420, and pectinase from A. niger; Cat. 18579; Fluka, Switzerland.) This digestion process took 1-6 days, depending on the age of the specimen. Heavily lignified vascular bundles are resistant to the enzymatic digestion and remain intact. This leaves the vasculatures, and the outer "shell" of the plant without any support, which thus collapse.

In order to preserve the vascular architecture, the stem segments when wet, were pre-glued by cyanoacrylate glue in a polystyrene frame prior to enzymatic digestion (Fig. 1-a). This prevents the vascular bundles from collapsing after the removal of parenchyma cells (Fig. 1-b). During the digestion process, tissue fragments were washed away by flushing the specimen gently with a Pasteur pipette. Figure 1-c shows the node region of Ohio43/KYS after digestion. Note the parallel bundles running through the node with branches before entering the node from below.

Figure 1. Undigested (a) and partially digested (b) stem sections glued into polystyrene frames. (c) Digested nodal region, note the straight through vasculatures.
 
 

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