Ligustrum leaf


This is an example of a mesomorphic dicotyledonous foliage leaf.

The midrib contains a single, large collateral vein. Here and on the lamina the upper epidermis (ADE) has a thick cuticle, the lower epidermis (LE) has a much thinner one - why do you think this is so? 

Note the mesophyll which is organized into a palisade (upper) and a spongy (lower) mesophyll. Palisade cells are arranged vertically, standing on their end walls, whilst spongy mesophyll is much more loosely and randomly arranged in this leaf. Note the large intercellular spaces (IS) between these cells and above the stomata. The vertical arrangement of the palisade cells means that many of the chloroplasts within the mesophyll cells are shaded from direct sunlight - thus reducing the number of mole quanta of light reaching them, and thus limiting light damage to the sensitive photosynthetic machinery within the chloroplasts themselves 

The two veins that you can see in this micrograph are embedded between the palisade and spongy mesophyll. They are therefore classified as minor veins. The vein on the left (inside the red ellipse) has been cut obliquely, and will join the one on the right at some point.

Click here to see an image of guard cells  as seen with the transmission electron microscope.