Short Notes On Anatomy Of Dicot Stems in Plants - 12th Biology Notes

      Anatomy Of Dicot Stems In Plants 

Good Morning Students ! 

Do you know what is anatomy ? 

What is Anatomy?

Anatomy is the study of the internal structure of living organisms. When we talk about anatomy in plants, we're referring to how the different parts of the plant's body are arranged and structured. Today, we're going to focus on the anatomy of a dicot stem in plants.

1. Epidermis

The epidermis is the outermost protective layer of the stem. It's the first line of defense against external factors. The epidermis is covered by a thin layer of cuticle, which helps in reducing water loss. It may also have a few stomata, which are tiny pores responsible for gas exchange.

2. Hypodermis

Just beneath the epidermis lies the hypodermis. This layer consists of collenchymatous cells, which provide mechanical strength to the young stem. These cells are thickened at the corners, making the stem rigid and helping it to stand upright.

3. Cortex

Next, we move inward to the cortex, which is located beneath the hypodermis. The cortex is made up of parenchymatous cells that are rounded and have thin walls. These cells are loosely packed with noticeable intercellular spaces, allowing for easy exchange of gases and storage of nutrients.

4. Endodermis

The endodermis is the innermost layer of the cortex. The cells here are rich in starch grains, and this layer is sometimes called the starch sheath. The endodermis plays a key role in controlling the flow of water and nutrients from the cortex into the vascular tissue.

5. Pericycle

Inside the endodermis, we find the pericycle, which is a layer of tissue just outside the vascular bundle. In dicot stems, the pericycle is made up of sclerenchyma cells that form semi-lunar patches. These cells provide additional support and help in the formation of lateral roots.

6. Vascular Bundles

The vascular bundles in dicot stems are conjoint, collateral, and open. This means the xylem and phloem are arranged side by side in the bundle, and there is a cambium between them, allowing for growth in thickness. The xylem is endarch, meaning the xylem vessels develop from the inside out. These vascular bundles are arranged in a ring around the central pith of the stem.

7. Pith

Finally, at the center of the stem is the pith, which consists of parenchymatous cells with large intercellular spaces. The pith functions primarily in the storage of water and nutrients, and its loose structure allows for the diffusion of substances throughout the stem.

 

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Mitochondria - The Powerhouse Of The Cell

                           Mitochondria Structure                                           

 Mitochondria are filamentous or granular cytoplasmic organelles called "the powerhouse of the cell" . Under light microscope mitochondria are seen in the form of thread like structure , therefore they are named as Mitochondria. 
Mitochondria was first observed by Kolliker in 1880 & later Fleming in 1882. The term Mitochondria was given by Benda (1897). 

Distribution -

Mitochondria are uniformly distributed in the cytoplasm of all eukaryotic cells. They are absent in the prokaryotic cells. 

Shape & Size -

Saucer & Oval are two common shapes of mitochondria are found in cells. The size of mitochondria is 1-10 0.5 micrometers (µm). 

Structure -

 Mitochondria is double membrane bound organelle. These membrane is made up of lipoprtiens. These membranes is seperated by an intermembrane space called Outer Compartment . The outer mitochondrial membrane forms outer boundry of mitochondria & the innermembrane is projected into the central space in the form of fingerlike projections called Cristae. The innermembrane lines the innermost compartment which is filled with the gel like matrix .

F₀-F₁ complex (also called ATP synthase) Or Oxysomes - The innermembrane & cristae are covered with special particles , known as F₁  particles. Each F₁  particle can be divided into base piece , stalk & head piece. 

Function - 

• The mitochondria perorms most important functions like oxidation , dehydrogenation , phosphorylation.
  
  
• Mitochondria are actual respiratory centers of the cells where the carbohydrates & fats are completely oxidized into CO2​ & H2​O. Energy released during this process is stored in the mitochondria in the form of ATP. The ATP is used in vital activities . Thus , mitochondria are called as ' Power House Of the Cell ".