Plant systematics is the scientific study of plants and how they evolve. The past and present of a plant are studied and documented. Why? It’s because the evolutionary history of a particular plant group can be easily traced. This is the primary goal of plant systematics.
Taxonomy is a term derived from the Greek word taxis which means ‘arrangement’ and nomos which means ‘law’. Taxonomy is the methodology and principles of the systematic way plants are classified. It allows us to classify plants within the hierarchy and subordinate groups.
Plants are classified for easy identification and are divided into taxonomic groups. These are morphological, anatomical, embryological, chromosomal, and chemical data. Both living and extinct plants are studied and classified in taxonomy.
5 Taxonomic Groups
Morphology
It relates to the branch of biology that deals with the form of living organisms, and the relationships between their structures. The size, shape, and structure of a plant or one of its parts assist in the classification of that plant.
Anatomical
It studies focuses on the structure of the plant and systems that make up a plant. A typical plant body consists of three major organs: the root, the stem, and the leaf. Other anatomical plant parts that assist in the systemic classification process include the reproductive parts like flowers, fruits, and seeds.
Embryological
It studies focuses on the origin and formation of new plants. Newly formed plants lack most structures like leaves, stems, and reproductive structures. The embryological study follows the plant from formation through maturity for classification purposes.
Chromosomal
It studies focuses on the DNA of a plant. The thread-like structures located inside the nucleus of plant cells carry all of the information about how a plant cell grows, thrives, and reproduces.
Chemical data
It is used to delineate the differences between species of plants. Chemical data may either support existing plant classification or may be used to help to classify new plant species.
Classification for Plant Systemics
There are three approaches to the systematic way plants are classified: cladistics, phenetics, and phyletics.
Cladistics
It relies on the evolutionary history behind a plant to classify it into a taxonomic group. Cladograms, also known as ‘family trees’, is a method of plant classification between plants according to the proportion of measurable characteristics that they have in common. The more characteristics that two plants share, the more recently they have been propagated from a common ancestor.
The family tree will note a common ancestor and outline which species have developed from the plant ancestor. All plants which have evolved from the ancestor will be in the same plant family, sharing distinct similarities along with new characteristics.
Phenetic taxonomy
It is a system of plant classification that searches for the overall similarity of compared plants. The plant history does not play an integral role in this classification method, phenetics deals with what the plants look like right now.
Phenetics comes from the Greek word phainein which means ‘to appear’. The appearance of the plant is studied in this classification approach to determine what plant family the studied specimen looks like currently. It’s not what the parent plants may have looked like.
Phyletics
It deals with the evolutionary change in a single line of descent without branching. It’s the most natural approach and assumes new species evolve gradually as plants adapt to the ever-changing environment. Phyletics does look to the plant history to clarify ancestors and determine descendants. This approach takes into account that unrelated species in similar ecosystems may grow to resemble one another in order to adapt to their environment. Single line evolution can change a plant’s appearance and characteristics to a certain extent.
Why Plants Are Classified
Plants can and do become extinct, and to have an accurate record of all plant life the plants must be classified.
A plant that was thought to be extinct may have deposited seeds somewhere that will germinate in years to come. Should that happen, we need an accurate and complete description of all known plants to determine what the plant may be. Is it a new plant species? The re-birth of an extinct plant? Or is it an old plant that has adapted and evolved into something better suited to the environment?
Records based on the three approaches of systematic plant classification will help us now, and in the future, to determine what plant species we are looking at and where it originated from.
If you missed Part 1 of 11, “Introduction To Horticulture and Propagation Methods”, click here.
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