Cross section in a leaf of Mentha piperita – peppermint.
Peppermint is an herbaceous from the Lamiaceae family, native to Europa. It is a hybrid mint that is a spontaneous cross between watermint and spearmint. It is a strongly aromatic perennial herb easy to grow, with a strong sweetish odor. The leaves are oval, dark green with sharp margins, unequally toothed. The leaves are especially good for their culinary properties but also for many medicinal uses.
Micrographs on this page are paraffin cross sections (10 μm thick) stained with astra blue and basic fuchsin.
Below : general aspect of the cross section.
Below: parts of the section at two magnifications showing the mesophyll, without midrib. It illustrates the different tissues: palissade parenchyma (pp) and spongy parenchyma (pl); epidermis (ep) of the two leaf faces, stomata (st). Chloroplasts in the two parenchyma are stained red.
A part of the section showing a secretory pelted trichome is also shown below on another micrograph.
Secretory pelted hair (trichome) on the adaxial face of the leaf.
On a paraffin section trichomes at the leaf surface are generally not preserved. A well suitable technique to observe well preserved trichomes on leaf surface is scanning electron microscopy. Micrographs below show a secretory pelted trichome (red circle) on the abaxial face.
St: stomata; blue arrow : sub stomatal chamber.ep1 et ep2: epidermis of ad and abaxial faces.