Monocots and dicots Difference (common and distinctive features)

Monocots and dicots Difference (common and distinctive features)

Angiosperms (flowering plants) are currently the dominant plants on Earth and number about 300,000 species, exceeding in this respect all other subdivisions of the plant world combined.

Angiosperms are divided into two classes – monocots and dicot plants. The differences between these classes can be summarized in a table.

Most monocotyledonous and dicotyledonous plants can easily be delimited from each other on these grounds. But in some representatives there is a combination of signs of monocotyledonous and dicotyledonous plants.

SignsMonocotsDicots
No. of cotyledonsOne cotyledons Two cotyledons
The usual number of members in flower circles3 + 3 A  3 + 3 G (3)5 C 5 A 5 + 5 G (5 )
VenationParallelCirrus (reticular)
Leaf structureWithout stipuleswith stipules
Arrangement of vascular bundlesScattered across the cross-section of the stemCyclic on the cross section of the stem
Vascular bundleClosedOpen
Table. Signs of monocots and dicots

Let’s consider the listed differences.

1. The number of cotyledons. Many typically dicotyledonous plants have a single cotyledon, such as buttercups. So in the cleaver ( Ficaria ), by all indications, it is a dicotyledonous plant, only one cotyledon.

Some mnogo plotnikov, such as the family of Nymphaeales ( Nymphaeaceae ), this feature – odnosemyadodnost – so constant that some taxonomists attributed them to monocots.

Studies in the middle of the 20th century established that the nymphaea have two cotyledons, but the first leaf of the bud occupies an apical (terminal) position, like the cotyledons in monocotyledons. One cotyledon is found in many other, more organized families of dicotyledonous plants (among umbellatus, poppies, etc.).

Thus, on the basis of only one trait – the number of cotyledons – we cannot classify the plant as monocotyledonous or dicotyledonous plants.

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2. Number of members in flower circles. Monocots are characterized by flowers of the three-membered type, dicots – flowers of the five-membered (sometimes four-membered) type.

In many dicotyledonous plants, flowers have large and indefinite pure members (families of buttercups, beech and birch ). The three-membered type of flower is also often found among dicotyledonous plants, for example, in the same cleaver ( Ficaria ranunculoides), but among monocots there are forms with four-membered flowers, for example, the raven eye ( lily family ). Thus, this feature, taken separately, cannot be decisive in clarifying the question of whether a plant belongs to monocotyledonous or dicotyledonous plants.

3. Venation. The reticulate venation, typical of dicots, occurs in many monocots, for example, in the lily family at the raven’s eye. On the other hand, in the plantain ( Plantago) , a dicotyledonous plant, the leaf venation is arched, like in monocots.

4. Location of vascular bundles. The vascular bundles in the stem of monocots are scattered without any order (on the transverse section of the stem in dicots, they are located in circles). 

However, in the cleaver ( Ficaria ) and in many other buttercups, in the nymphaeum, clove and other families of dicotyledonous, the bundles are scattered.

Consequently, this feature does not have an absolute meaning.

5. The structure of the vascular bundle. Botanical research has shown that many monocotyledonous plants with closed bundles (without cambium) in the adult state have primary cambium in the bundles in the early stages of development. This leads us to believe that monocots lost their cambium during their phylogenetic development.

Each of the listed characteristics, taken separately, therefore, does not give us the opportunity in many cases to classify plants as monocotyledonous or dicotyledonous plants. To resolve the issue, we must take into account a set of signs. Consequently, the relationship between monocotyledonous and dicotyledonous is not such that they can be considered independent, independent in origin. There is a certain genetic link between them.

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