figure

Figure 5.3 Transverse section of a pine needle. Note the simplicity of its venation in comparison to that of a grass (Figures 5.4 and 5.5) and a dicotyledon (Figure 5.7). A single central vein has two strands of phloem (p) and xylem (x), embedded in transfusion tissue (t).These vascular tissues are separated from chlorophyllous mesophyll (red) by an endodermis (e) with Casparian strips and suberised lamellae, through which water must pass outwards from the xylem and sugar must pass inwards to the phloem. Stomata in the epidermis appear bluish. Rhodamine B stain, fluorescence optics. Scale bar = 100 µm (Photograph courtesy M. McCully)