A dicotyledonous plant, commonly shortened to dicot, is one of the two major groups of flowering plants (angiosperms). The term “dicotyledon” literally means “two seed leaves,” derived from the trait present in the seed embryo. This characteristic was the original basis for classifying these plants, which comprise the majority of familiar flowering species.
The dicots are scientifically recognized as the eudicots in modern classifications, a group that includes over 175,000 established species, ranging from tiny herbs to massive trees. These plants develop a set of distinguishing anatomical features that allow botanists to classify them accurately throughout their life cycle. These structural differences affect how the plant grows, transports nutrients, and reproduces.
The Five Defining Structural Traits
The number of cotyledons, or embryonic leaves, is the feature that gives the plant its name, as dicots consistently possess two inside their seed. These paired leaves are the first structures to emerge upon germination, supplying initial nourishment to the seedling before its true leaves develop and begin photosynthesis.
Examining a mature leaf reveals a net-like or reticulate venation pattern, which is the branching arrangement of the veins. These veins diverge from a prominent central midrib, creating an intricate, interconnected network that efficiently distributes water and nutrients across the leaf surface.
The stem’s internal architecture is defined by its vascular bundles, the tissues responsible for transporting water and food. In a dicot stem, these bundles are organized in a distinct ring formation just beneath the outer layers. This arrangement includes a layer of cambium tissue, which allows for secondary growth, enabling the stem to increase in girth and often develop into woody structures like tree trunks.
Underground, dicots typically establish a taproot system, which develops from the primary root structure (radicle) of the embryo. This system is characterized by a single, thick, dominant root that grows deep into the soil, with smaller lateral roots branching off to the sides. The taproot provides firm anchorage and allows the plant to access deeper water reserves.
Flower structures in dicots are typically arranged in multiples of four or five. Flowers with five parts, such as the rose or apple blossom, are particularly common within this group. This specific numerical pattern aids in quickly identifying a plant as a dicotyledon.
Dicotyledons Versus Monocotyledons
The structural differences between dicots and the other major class of flowering plants, monocotyledons, are consistent across all five major features. While dicots start with two cotyledons, monocots begin with only a single embryonic leaf in their seed.
In contrast to the dicot’s branching, net-like venation, monocot leaves exhibit parallel venation, where the main veins run alongside each other from the base to the tip of the leaf. The internal stem structure also varies significantly, as monocot vascular bundles are scattered seemingly at random throughout the stem tissue, lacking the organized ring formation seen in dicots.
The root systems of the two groups are also functionally different, with monocots forming a fibrous root system composed of many thin, equal-sized roots that spread out close to the soil surface. This is unlike the singular, deep taproot that characterizes most dicots. Finally, a monocot flower will almost always have its parts arranged in multiples of three, a stark contrast to the multiples of four or five found in dicot flowers.
Where We Find Dicots
Dicotyledonous plants dominate much of the terrestrial flora. Most of the world’s familiar broad-leaf trees, such as oaks, maples, and walnuts, are dicots, capable of increasing their trunk width thanks to the ringed vascular structure. This group also includes many cultivated food crops, making them economically significant across the globe.
Common examples encountered daily include vegetables like beans, peas, and carrots, as well as fruits such as apples, grapes, and mangoes. Many popular ornamental plants, including roses, sunflowers, and geraniums, also fall into the dicot category.