Anatomy is the branch of science which deals with the study of the internal organisation of plants and animals. Plant anatomy deals with the detailed study of plants, such as the cell structure, cross sections of root, leaf and stem, etc. While it is supported by the study of morphology as the basis, anatomical studies use the help of the microscope for 99.9% of its data. Robert Hooke who first invented the microscope is also instrumental in giving the first report of a plant cell; its discovery.
The anatomy of plant studies follows a simple pattern; that is, there is an order or series of plant organs taken into consideration, starting from the cell.
1. The Plant Cell:
The cell is the functional and structural unit of an organism or plant. In plants, there might be one cell or many cells depending on the type and species. Whatever the number of cells present, plant cells exhibit the presence of protoplasm as the physical, functional basis of life in the plant. It is considered the physical basis of heredity, with characteristic features passed down from parent(s) to offspring.
Anatomical studies of the plant cell wall will also highlight details of the type of cell wall, thickening, layers, secondary wall (if present), pits and pit formations, the plasma membrane, ribosomes, Golgi-bodies, plastids, chloroplast, mitochondria, the nucleus, and non living inclusions in the cell. These studies are also supported by cytological studies which shows how the cells divide; mitotic or meiotic divisions.
2. Plant Tissue:
Plant tissue may vary from lower forms of plants as being simple to very complex tissue forms in higher plants. The most basic types of tissues studied are parenchyma, collenchyma and sclerenchyma. Parenchyma act as a protective layer, and also provides storage os starch, proteins oils, etc. Collenchyma not only improves the turgidity of the plant, but is rich in cellulose and also performs the function of water storage. Sclerenchyma acts as the structural support for the plant giving the plant the necessary strength to stand upright and also to withstand external pressure of rain, wind and applied external forces.
In addition to these tissues, anotomical studies of plants alao gives details of tissue like the xylem and phloem of higher plants, namely the vascular plants. Meristems, another kind of tissue dealing with the growth and multiplication of cells in particular areas of the plant, are also easily studied. With the help of anatomical studies, one can observe the areas of meristematic tissue; lateral, apical, etc.
3. The Primary Plant Body:
Cross sections and lateral sections for microscope studies reveal the formation of tissue growth, positions of different tissues in the plant organ, layers and types of tissues seen in different levels such as epidermis, cortex, endodermis, pericycle, and pith, and also the position of the vascular tissue in the plant organ, such as where the phloem and xylem are located.
4. The Stem:
Lower order of plants do not have a well differentiated stem, but in higher plants especially seen in monocotyledons and dicotyledons, there is a well differentiated stem observed. Anatomical plant studies of the stem reveal details such as the epidermis, cortex, endodermis, stele, xylem, phloem and cambium. The parenchyma, collenchyma and sclerenchyma may be observed at specific areas of the plant in the different stem layers.
5. The Root:
Tissues in the roots are similar to those found in the stem, except that in the way it is positioned for its respective purposes. Root hairs may be observed, air sacs may be present and the vascular tissues may not be in the form of bundles as seen in stems, but scattered with the phloem and xylem separate. In monocotyledons, the vascular tissue may also be seen as meta-xylem and meta-phloem.
6. The Leaf:
Leaves vary from one plant to another not only in their external appearance, but also in the way the leaf tissues are organized. the various layers and tissues present may be the epidermis, stomata, cuticle, air spaces, palisade tissue, spongy parenchyma, lower epidermis and vascular tissues.
In order to identify a plant by way of anatomical studies, the above mentioned features have to be observed and studied in detail. Depending on the type of plant and the function its organs serve, the features / organs / tissues will show degrees of differences or comparisons.