Download ACP Level 1 Plant Structure and the Oil Cell

ACP-1 Plant Structure and the
Oil Cell
Plant Structure and the Oil Cell
The simplest structure consists of one single cell.
Pictured here is the leaf of a magnolia that has
individual cells that produce essential oil.
Each vacuole is equipped with a membrane. The cells
are isolated and are surrounded by another internal
cellular structure. Biosynthesis of all the constituents
of the essential oil takes place in the plastids (same
type as the organelle chloroplasts) and in the
cytoplasm of the oil-producing cell.
Plants such as Eucalyptus, possess a cavity surrounded by a large number of oil producing cells within
the plant structure. These so-called excretory cavities is the place where the plant produced essential
oil are stored.
Pictured above is the secretory cavity in a citrus peel.
Even citrus fruits like orange have such cavities lying in the epidermis of the peel. This
also explains that when peeling an orange you smell citrus-like odors.
Lavender oil gland
In the Labiatae family, and thus all kinds of lavender, the oil comes from a very different
structure. On the epidermis of the plant, it contains spherical glands with two cells
connected to the epidermis cells.
Figure 3: Glandular trichomes in Lamiaceae. o=oil drop, sc=subcuticular storage cavitiy, h=head cells
(site of terpene biosynthesis), s= stem and b= basal cells. (Modified after Fahn, 1979a)
Marjoram SEM photo
Stems and flowers of flowering plants are also littered with these glands. Here is a photo of
marjoram (Origanum Majorana) with a scanning electron microscope (SEM) and below is a
photo of rosemary. Such structure also explains that if you touch a plant essential oil is
released. Even with a plant like lavender, when dried, the lavender oil stored in the glands will be
released when squeezed.
In this photo is a cross section of a needle of a conifer.
Secretory ducts are a more complex structure. Channel-like structures like this are found in the
conifers. Such ducts make a connection from the roots of the tree to the leaf, flower and fruit.
This photo is magnification of ducts in wormwood. There are two ducts here. The one on the left is old
enough to have developed a small lumen and epithelium; the one on the right has not yet reached the
stage of having a lumen. The arrow points to an area where the cells might be starting to pull apart –
the black material between the cells might be the first stages of the breakdown of the middle lamella
(there are places in the upper part of this micrograph where there are similar amounts of dark
material between cells.
This photo is a transverse section of the needle leaf of pine (Pinus). The needles of pines and many
other conifers have resin canals with complex epithelia.
These channels are composed of an epithelium which surrounds a central cavity. Some of these cells
forming the wall of the cavity will change into secretory epithelial cells. The oils are biosynthesized within
their leucoplasts and move via the endoplasmic reticulum into the cavity. The ducts are relatively
close to the surface of
the leaf. Not without reason,
the smallest animals will take off immediately after
a bite out of a pine needle because of the bitter taste which is given by the resins. This is a way of protection
for conifers.
Source: http://distillingherbs.blogspot.com/2011/02/plant-secretory-structures.html
Special Thanks to Henk Ploeger, who works as an educator and in his spare time distills essential oils from
plant parts by steam distillation. He enjoys reading and studying about the herbs and their medicinal uses.