Dicotyledonous plants | Definition, Characteristics, Examples And Evolution

Dicotyledonous plants, also known as dicots, are one of the two groups into which all the flowering plants or angiosperms were formerly divided. The name refers to one of the typical characteristics of the group, namely that the seed has two embryonic leaves or cotyledons.

There are about 175,000 known species of dicots. Most common garden plants, shrubs and trees, and broad-leafed flowering plants such as magnolias, roses, geraniums, and hollyhocks are dicots.

Definition of dicotyledonous plants

Dicotyledonous plants can be defined as a major group of flowering plants whose members typically have two cotyledons, or embryonic leaves, in their seeds, and whose flowers generally have parts in fours or fives, or multiplies thereof. Flowering plants that are not dicotyledons are known to be monocotyledons, a flowering plant group whose seed typically contains one cotyledon.

Dicots typically also have flower parts (sepals, petals, stamens, and pistils) based on a plan of four or five, or multiples thereof, although there are exceptions. The leaves are net-veined in most, which means the vessels that conduct water and food show a mesh-like pattern. In the stems the vessels are usually arranged in a continuous ring near the stem surface.

About 50 percent of all dicot species are woody; they show an annual increase in stem diameter as a result of the production of new tissue by the cambium, a layer of cells that remain capable of division throughout the life of these plants. Branching of stems is common, as are taproots.

The microscopic pores (stomates) on the leaf surfaces are usually scattered and are in various orientations. The pollen grains typically have three furrows or pores (tricolpate condition), except in the more primitive families.

History of dicotyledonous plants

Traditionally, the dicots have been called the Dicotyledones (or Dicotyledoneae), at any rank. If treated as a class, as they are within the Cronquist system, they could be called the Magnoliopsida after the type genus Magnolia.

In some schemes, the eudicots were either treated as a separate class, the Rosopsida (type genus Rosa), or as several separate classes. The remaining dicots (palaeodicots or basal angiosperms) may be kept in a single paraphyletic class, called Magnoliopsida, or further divided. Some botanists prefer to retain the dicotyledons as a valid class, arguing its practicality and that it makes evolutionary sense.

Read also: Difference between monocotyledons and dicotyledons

Characteristics of dicotyledonous plants

The characteristics include;

1. The seeds are divided into two halves.
2. They have two seed leaves or cotyledon.
3. Flower plants are in multiples of four or five.
4. Major leaf veins are reticulated.
5. They have (3) three furrows or pores in it’s pollen (triporate).
6. The root of the dicots is usually primary tap root system
7. The dicot plant show secondary growth in the stem and root so as to increase the girth of the plant body.
8. The vascular cambium is present which later give rise to the secondary xylem and phloem.
9. The floral whorls are found as four or five or a multiple of it.
10. The stem possesses the vascular bundle arranged in a ring pattern.
11. Limited number of vascular bundles or xylem and phloem groups is seen.
12. The pith is absent in the root.

Read also: Meaning and importance of agriculture

Examples of dicotyledons

Some examples of dicotyledonous plants include;

1. Legumes (pea, beans, lentils, peanuts)
2. Daisies
3. Mint
4. Lettuce
5. Tomato
6. Oak
7. Pea
8. Tamarind
9. Mango
10. Rose
11. Neem
12. And so on

The bottom line

Dicotyledonous plants are a group of flowering plants belonging to the class Magnoliopsida of Angiospermae (angiosperms), characterized by having two photosynthetic cotyledons in the seed that may emerge from the ground when the seed germinates. Examples include;  beans, buttercups, oaks, sunflowers, etc.

Read also: Classification of crops