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Difference Between Monocot and Dicot Stem

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What are Monocotyledons and Dicotyledons?

IVSAT 2024

All flowering plants can broadly be divided into two divisions. They are monocots or monocotyledons and dicot or dicotyledons. Cotyledons are a very important segment of the embryo that lies within the plant’s seed. The structure of the monocot and dicot stem is quite different from each other. 

 

The plants having seeds with two cotyledons are known as dicots, whereas monocots are the plants whose seeds have a single cotyledon. Legumes (like peanuts, beans, lentils), lettuce, mint, tomato, and the like are typical examples of dicots. Again, pulses (including millet, corn, and rice), sugarcane, palm, banana, grass, and the like are an example of monocots. The ‘cot’ of the plants is actually an embryonic leaf. The cots work to feed the germinating seedlings. This is because the root system of the young plants remains underdeveloped. There are certain differences between the anatomy of monocot and dicot plants. There are differences between monocot stem and dicot stem, as well.

 

Monocot Stems

In the case of monocot stems, they come with scattered vascular bundles. When the monocot plants mature, they slowly start generating fresh vascular bundles. The bundles are closed and conjoint in structure. They do not come with piths, or the food-transporting tissues in the stalks of young vascular plants. So the vascular bundle’s stores nutrients within the vascular bundles. Tulips, onions, lilies, and garlic are examples of monocot stems. However:

  • The stems in monocot plants have sclerenchymatous hypodermis or layers of sclerenchyma tissues. 

  • They work to check water loss from leaves. 

  • The layers of the tissues are guarded by bundle sheath and noticeable parenchymatous tissues. 

  • The thick parenchymatous layers transport plant nutrients. 

 

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Dicot Stems

There is a pith zone in the dicot stem. It works as the core around which the intricate vascular bundles are arranged to form a ring. In every bundle of the vascular bundle of a dicot stem, the nutrient-bearing xylem and phloem tissues are kept apart by means of the vascular cambium. Sunflower and Cucurbita are examples of dicot stems. As the plants mature, the older plant cells are pushed to the edges of the stem. This elongates the vascular bundles. Some more structural features make monocot and dicot stem unique in their own ways. For example:

  • The stems have an outer protective layer, called Epidermis.

  • The innermost part is called the pericycle.

  • The cells in a dicot stem are arranged in different layers. They can be sub-divided into three zones, namely Hypodermis, Cortical Layers, and Endodermis.

  • The hypodermis, containing collenchyma cells, strengthens the new stems.

  • Cortical layers, with thin layers of parenchymatous cells, help in the absorption of nutrients and water.

  • The ‘starch sheath,’ or endodermis regulates hormone movement, as well as the movement of ions and water in and out of the plant’s vascular system. It also aids in storing plant starch.

  • The pericycle present within the inner Endodermis offers optimum support and protection to the young plant.

 

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Structure of Monocot and Dicot Stem

Epidermis

  • The epidermis is the stem's outermost covering, made up of a single layer of thin-walled cells packed tightly together with no intercellular gaps.

  • The epidermis cells lack chlorophyll, but some of them have been changed to form multicellular hairs or trichomes. Monocot stems are devoid of trichomes.

  • Because monocots do not go through secondary growth, their epidermis stays the same throughout their lives. Dicots' epidermis may be replaced during secondary growth.


Cortex

  • The existence of different sections and the quantity and type of cells in the cortex of monocot and dicot stems differ greatly.

  • The cortex of the dicot stem is divided into three sections: hypodermis, general cortex, and endodermis.

  • The hypodermis is the only component of the cortex in monocot stems. Sclerenchymatous cells make up the hypodermis, which is made up of 2-3 layers.

  • The monocot stem's hypodermis is stiffer, while the dicot stem's hypodermis is more flexible.


Ground Tissue

  • Ground tissue in monocot stems is not divided into units such as pericycles and medullary rays.

  • The ground tissue is a mass of parenchymatous cells that extends up to the center of the hypodermis.

  • The cells are spherical, thin-walled, and loosely organized with intercellular gaps. The arterial bundles stuck in this location use the ground tissue as a matrix.

  • The ground tissue of the dicot stem is divided into three categories: pericycle, medullary rays, and pith.


Pericycle

  • The tissue that occurs between the endodermis and the vascular bundles is known as the pericycle. The pericycle in the dicot stem is multilayered and serves to protect the underlying tissues.

  • Because the pericycle's cells are sclerenchymatous, it's sometimes referred to as hardback. The pericycle's sclerenchymatous cells appear in the shape of semilunar patches above the vascular bundles.


Vascular Bundles

  • The quantity, arrangement, and components of vascular bundles change greatly between monocot and dicot stems.

  • The dicot stem's vascular bundles form a ring around the central pith beneath the pericycle.

  • Wedge-shaped, conjoint, collateral, and open vascular bundles. The dicot stem's stele is of the eustele type.

  • The monocot stem has multiple vascular bundles that are dispersed throughout the ground tissue and cortex. The monocot stem's stele is of the atactostele type.


Pith

  • The pith is the cell's centre mass, which in dicot plants is well developed, but in monocot stems is smaller and less distinct.

  • The cells are parenchymatous and appear in the form of medullary rays around the arterial bundles.

  • The cells might be spherical or polygonal, and they can have or not have intercellular gaps. The pith region's cells store food and aid in the transport of food and water between the bundles.


There are a number of differences between monocot and dicot stem. They can be discussed as the following:

 

Difference Between Monocot Stems and Dicot Stems

Monocot Stems 

Dicot Stems

The vascular bundles are present in a scattered manner, without a specific arrangement. 

The vascular bundles have a specific shape. They are also arranged in the form of one or two rings.

The vascular bundles of the stem are seen in the periphery. These bundles remain guarded by a thick parenchymal layer. However, they have no definite shape.

The wedge-shaped vascular bundles form a ring-like arrangement. They surround a layer of parenchymal tissues. 

Pith is never present.

There are pith regions.

Bundle sheath is present.

Bundle sheath is absent.

The hypodermis region is composed of sclerenchyma cells.

The hypodermis region comprises collenchymas cells.

Do not generate secondary thickening. So the stems do not widen much.  There are, however, exceptions like palm and bamboo trees.

Many of the dicot plants can undergo secondary thickening. So all flowering plants with rather thick and woody stems are dicots. 

Plants cannot form radicals. Hence, the roots crop up from the stem’s nodes. 

The lower portion of the seedling’s embryo creates a radical. The roots of the plants are produced from there. 

Pericycle and phloem parenchyma is not present.


Pericycle and phloem parenchyma there.

The vessels have a round or oval shape. They are arranged in a Y-shaped pattern.

The vessels are polygonal in shape. They are arranged in a row or chain shape.

Medullary rays are not present.

Medullary rays are seen between the vascular bundles. They help in radial conduction.


Functions of Monocot and Dicot Stem:

  • The stem is a plant's central shaft, supporting many parts and appendages such as leaves, branches, flowers, and fruits.

  • Food is transported from the leaves to various parts of the plant via the stem, while water is transported from the roots to various sections of the plant via the stem.

  • Some plants' young stems are photosynthetic and can help the plant prepare nourishment.

  • A huge number of food particles, such as starch and other nutrients, are stored in the stem cells.

  • Stems in some plants are designed for specific activities such as climbing and food storage.

  • The stem's meristem tissue continues to expand, generating new live tissue each year to ensure the plant's continued growth.

  • The stomata in the stem play a role in transpiration and aid in the removal of surplus water.

  • To prevent water loss, plants with a modified stem, similar to cactus, store a huge amount of water and food in the stem.

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FAQs on Difference Between Monocot and Dicot Stem

1. What are the Medullary Rays? 

They are vertical rows of parenchymal cells. They run through the vascular tissues of stems and roots in the plants. They work to transport and store plant nutrients.

2. What is radical in plants?

It is the very first part of a maturing plant embryo or seedling. During germination, radicals are the first elements to come out of the seeds.

3. What are Xylem and Phloem?

They are present in the roots and the stems of plants. Typically, Xylem lies within the interior of the stem, while the phloem is present on the exterior. Xylem is responsible for carrying minerals and water to the leaves from the roots. Phloem takes the organic nutrients and glucose from the leaves and transports the nutrients to the other parts of the plant. 

4. What is Parenchyma?

These thin-walled plant tissues are primarily seen in the cortex, pith, or pericycle of the stems and roots. They conduct most of the metabolic activities in a plant.

5. What is Sclerenchyma? 

They are relatively thick and have strong plant tissue. They give optimum support to the plant.

6. What is Collenchyma? 

They are primarily present in the ‘growing parts’ of a plant, such as shoots and leaves. They give additional support to the plants. There is a fundamental difference between sclerenchyma and collenchyma. Unlike sclerenchyma, these tissues generally consist of thin walls, with irregular, thick patches in the spots where secondary growth is feasible.


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