Monocotyledons, also referred to as monocots, are flowering plants bearing seeds with a single cotyledon or embryonic leaf.
- There are about 60,000 species of monocotyledonous plants found worldwide where the family Orchidaceae consisting of orchids forms the largest group in both monocots and in angiosperms with about 20,000 species.
- The second most abundant monocotyledons include grasses in the family Poaceae which are the most economically important of them all.
- Monocotyledon plants form the largest biomass within agriculture including most grains like wheat, rice, barley, along with forage grasses, sugarcane, and bamboos.
- All monocots share a common evolutionary history, making them a monophyletic group.
- The most common characteristic associated with monocotyledons is the presence of a single cotyledon in the embryo of the seed with parallel-veined leaves.
- The leaves are more slender where they are sheathed at the base without any petiole. The veins move in a parallel pattern but are smaller in size with even smaller veins connecting them.
- Besides, they have scattered vascular bundles in the stem with an adventitious root system with no cambium.
- The lack of lateral meristem or cambium limits the growth of stems in diameter with height. As a result, most monocotyledons are herbaceous plants with some arboraceous plants like agaves, palms, and bamboos.
- Typically, monocots have an epidermis with a thick cuticle, but they lack epidermal hairs. The cells in the epidermis or the hypodermis are not arranged in concentric circles
- The flowers are also different from dicots in that the parts of the flowers usually occur in the set of three.
- Commonly, the number of petals and sepals is either three of multiple of three, whereas the pistil and stamen can be numerous. There are six stamens that represent two whorls of three.
- Sometimes, there might be a single ovary with two carpels instead of three.
- The pollen grains in monocots characteristically have a single furrow or aperture in contrast to other angiosperms.
- The resulting embryo has a single embryonic leaf almost always with an endosperm.
- The most common and economically important monocots include plants like bananas, gingers, turmeric, cardamom, asparagus, along with some household plants like epiphytes and decorative flowers like lilies and tulips.
Dicotyledons, also referred to as dicots, are flowering plants bearing seeds with two cotyledons or embryonic leaves.
- It is the largest group within angiosperms consisting of about 200,000 species of flowering plants.
- Unlike monocots, dicots are not a group of plants arising from a single ancestor; rather, they are assumed to have evolved from different lineages. Thus dicots are paraphyletic.
- The types of plants in dicots range from garden plants, shrubs, and herbs to broadleaf plants like roses and geraniums.
- Some economically important plants like peas, beans, roses, daisies, and oak trees are dicots.
- The most important characteristic in all dicots is the presence of two embryonic seed leaves or cotyledons along with reticulate veined leaves.
- The leaves in dicots are broader than long and have net-like reticulate venation. The veins form a finely branched network through the leaf blade with finer veins in between the major ones.
- Dicots are capable of secondary growth due to the presence of the lateral meristem or cambium. The cambium goes on to produce new cells in concentric circles, increasing the girth of the plant.
- The stem in dicots is composed of multicellular epidermal hairs all over the epidermis with vascular tissues arranged in concentric circles.
- The vascular bundles are arranged in the order of four or eight primarily arranged towards the perimeter of the stem.
- Dicots have a tap root system with a long deep primary root growing into finer secondary roots.
- The flowers in dicots are tetramerous or pentamerous in that the parts occur in the set of four or five.
- Typically, the number of petals and sepals is either four or five or their multiples, whereas the pistil and stamen can be numerous.
- The pollen grains are tricolpate, meaning they have three ridges or furrows that go through the outer layer.
- The number of seeds in dicots will also be more than that in monocots where the endosperm may or may not be present.
- In the absence of endosperm, the two cotyledons provide the necessary nutrients to the seed.
Key Differences (Monocotyledons vs Dicotyledons)
Basis for Comparison
|Definition||Monocotyledons are flowering plants or angiosperms bearing seeds with a single cotyledon or embryonic leaf.||Dicotyledons are flowering plants or angiosperms bearing seeds with two cotyledons or embryonic leaves.|
|Also called||Monocotyledonous plants are also referred to as monocots.||Dicotyledonous plants are also referred to as dicots.|
|Species||Monocotyledon is a smaller group of flowering plants with 60,000 species of plants.||Dicotyledon is a larger group of flowering plants with about 200,000 species of plants.|
|Root||Monocots have an adventitious or fibrous root system.||Most dicots have a tap root system. However, some dicots have an adventitious root system.|
|Vascular bundles||In monocots, the root has about 8-10 vascular bundles.||In dicots, the root has about 2-4 vascular bundles.|
|Stem||The stem in most monocots is herbaceous. But, some plants have arboraceous stems.||The stems in dicots are either herbaceous or arboraceous.|
|The Monocot stem is unbranched and fleshy.||Dicot stem is branched and hard.|
|Within the stem of monocots, the vascular bundles are scattered in no particular pattern.||Within the stem of dicots, the vascular bundles are arranged in concentric circles.|
|Most monocot stems lack a lateral meristem or cambium.||A lateral meristem or cambium is present in the stems of dicot plants.|
|Cambium, if present, is not differentiated into cortex or stellar regions.||The cambium is differentiated into the cortex and stellar regions.|
|Epidermal hairs are absent.||Epidermal hairs are present.|
|Secondary growth||Monocots do not undergo secondary growth due to the absence of cambium.||Secondary growth occurs in dicots as the cambium is present.|
|The leaf in monocots is isobilateral in symmetry.||The leaf in dicots is dorsoventrally flattened.|
|Monocots usually have long, narrow, and slender leaves.||Dicots usually have broad leaves, but the shape and size of the leaves vary according to the species.|
|Monocot leaves have stomata on both upper and lower surfaces and thus are termed amphistomatous.||Dicot leaves have stomata only on one of the surfaces of the leaf and thus, are termed epistomatous.|
|Venation||The leaves have a parallel venation system.||The leaves have a reticulate venation system.|
|Flowers||Monocot flowers are usually trimerous, meaning the number of parts of the flowers is either three or it’s multiple.||Dicot flowers are usually tetramerous or pentamerous, meaning the number of the flower parts is either five or four or their multiple.|
|In some monocot plants, calyx and corolla are undifferentiated, and a perianth is present instead of them.||The calyx and corolla in dicot plants are differentiated completely.|
|The flowers in monocots are usually wind-pollinated.||The flowers in dicot plants are usually insect-pollinated.|
|Pollen grains||The pollen grain is monocolpate with a single furrow or ridge on the pollen tube.||The pollen grain is tricolpate with three or more furrows or ridges on the pollen tube.|
|Germination||The seed germination in the monocot embryo is hypogeal.||The seed germination in the dicot embryo is either hypogeal or epigeal.|
|Embryo||The embryo in monocots contains only one cotyledon or seed leaves.||The embryo in dicots contains two cotyledons or seed leaves.|
|Embryo produces a single leaf that grows as a long and narrow structure during germination.||Embryo produces two seeds that develop into different shapes than their true leaf.|
|Endosperm||The endosperm is always present and is usually large.||The endosperm may or may not be present and is usually small.|
|Fruit||Trilocular fruit is found in monocotyledons.||Pentalocular fruit is found in dicotyledons.|
|Examples||Bamboos, bananas, asparagus, ginger, tulips, lilies, palms are some examples of monocots.||Roses, oak trees, daisies, peas, beans, cactus are some examples of dicots.|
Examples of Monocots
- Grasses are a group of flowering plants that form small flowers and have monocotyledonous seeds.
- Grasses are one of the most economically important groups of flowering plants consisting of cash crops like wheat, barley, and rice.
- The seeds in these plants have a single cotyledon or embryonic leaves.
- Grasses have all the characteristics of monocotyledonous plants with long narrow leaves and fibrous root systems.
- The flowers in grasses are not the most obvious as the flowers lack petals and sepals. However, these are flowering plants with small flowers.
- Grasses belong to the Poaceae family, which is the second-largest group of flowering plants among all monocots.
- Lilies are flowering plants that are monocotyledonous with a single cotyledon in their embryo or seed.
- Lilies have all the characteristics of monocots with leaves with parallel venation and an adventitious root system.
- Additionally, the flowers in lilies are trimerous with the number of petals and sepals in the multiple of three.
- The plant is small and herbaceous, which is characteristic of all monocots.
- Some lilies, however, have different flowers making it difficult to distinguish them from other dicots.
- Sometimes, it looks as the flower is formed of a single petal. The petal is a modified leaf termed spathe, underneath which are the real petals.
Examples of Dicots
- Legumes are one of the most important groups of dicotyledonous plants. These belong to the Leguminosae family of flowering plants where the seeds of the plants act as the fruit.
- Dry legumes are also termed pulses.
- Legumes are mostly grown for human consumption, for livestock, or as soil-enhancing fertilizers.
- These plants, like most dicots, have a tap root system where the roots exist in a symbiotic relationship with nitrogen-fixing bacteria in the form of root nodules.
- The symbiotic relation allows an important agricultural phenomenon called crop rotation.
- The fruit in legumes is biologically unique where a simple dry fruit is developed from a single carpel.
- The most common legumes include peas, beans, lentils, soybeans, chickpeas, clover, etc.
- Cactus is also dicotyledons with small pentamerous flowers that exist for a short period of time during their lifecycle.
- Cactus, plural cacti, is a desert plant that is capable of surviving on a limited supply of water.
- The flowers in cacti may not always be the same as some flowers are known to have numerous petals and stamens.
- However, when examined carefully, some cacti have pentamerous flowers with five petals and sepals.
- Besides, the root system in the cactus is a tap root system with a primary root divided into numerous secondary and tertiary roots. This branching allows the plants to absorb some water that might be present deep under the earth’s surface.
- The venation in the leaves is no distinguishable as the leaves are modified to reduce and prevent water loss.
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