Plant Root Morphology Lecture Notes PDF

# Plant Root Morphology ## Root Types - **Taproot:** This is the main root that grows straight down and is usually larger than the other roots. It acts as an anchor for the plant and absorbs water and nutrients. - **Root cap:** This is a protective layer that covers the tip of the taproot. It...

# Plant Root Morphology ## Root Types - **Taproot:** This is the main root that grows straight down and is usually larger than the other roots. It acts as an anchor for the plant and absorbs water and nutrients. - **Root cap:** This is a protective layer that covers the tip of the taproot. It helps to protect the root as it pushes through the soil. - **Main root:** This is the main body of the taproot. It is responsible for absorbing water and nutrients from the soil. - **Fibrous Root:** These are a network of thin roots that grow from the base of the stem. They are more shallow than taproots and help to hold the plant in place. - **Lateral roots:** A fibrous root system is characterized by the absence of a single primary root. - **Adventitious Root:** These are roots that arise from unusual places, such as the stem or leaves. They can help to support the plant or can help to absorb water and nutrients in dry conditions. ## Parts of a Root - **Root hair:** These are tiny extensions of the root that increase the surface area for absorption - **Piliferous layer:** The outer layer of the root that contains the root hairs - **Cortex:** The layer lying beneath the piliferous layer which helps in the storage of food and water. - **Endodermis:** The innermost layer of the cortex - **Pericycle:** The layer that lies beneath the endodermis and forms the lateral roots - **Stele:** The central core of the root that contains the xylem and phloem ## Primary Root - The primary root or taproot has an **arch Cambium** and a **Stellate Cambium** - **Circular Cambium:** This forms a circular ring - **Collapsed Xylem:** This is formed by the breakdown of old cells. - The circular cambium grows outwardly to produce additional cell layers of xylem. - **2nd Phloem:** This phloem forms on the **outside** of the circular cambium from old xylem. - **2nd Xylem:** This xylem forms on the **inside** of the circular cambium from old phloem ## Root Tissues - **Parenchyma:** This is the most common type of plant tissue. It is made up of thin-walled cells and is responsible for storage, photosynthesis, and respiration. - **Collenchyma:** This tissue is made up of cells with thickened walls and is responsible for providing support to the plant. - **Sclerenchyma:** This tissue is made up of cells with very thick walls and is responsible for providing strength and support to the plant. ## Root Structure - **Primary growth** results in an increase in length of the root - **Secondary growth** results in an increase in girth of the root and involves formation of **vascular cambium** (**cambium**) - **Vascular cambium** forms between the xylem and phloem and produces secondary xylem (wood) and phloem (bark). ## Types of Root Systems - **Taproot system:** This system is characterized by the presence of a large, primary root that grows straight down. - **Fibrous root system:** This system is characterized by a network of thin, adventitious roots that grow from the base of the stem. - **Adventitious root system:** This system is characterized by roots that grow from unusual places, such as the stem or leaves. ## Functions of Roots - **Anchorage:** Roots help to anchor the plant in the soil, preventing it from being blown over by wind or washed away by rain. - **Absorption:** Roots absorb water and nutrients from the soil. - **Storage:** Roots can store food and water for the plant. - **Conduction:** Roots conduct water and nutrients from the soil to the rest of the plant. ## Epidermis - Epidermis forms the outermost layer of the root. - Epidermis has root hairs which help in absorption and protect the root from damage. ## Pericyle - Pericycle is a layer of cells that is located just inside the endodermis. - Pericycle is responsible for the development of the lateral roots. ## Stele - Stele is the central core of the root - It contains the xylem, phloem, and cambium - Xylem and phloem are responsible for the transport of water and nutrients throughout the plant. ## Notes - **Lork:** Cork is a protective tissue that covers the outside of the root. - **Calyptra:** This refers to a cap that covers the root tip. - **Plumale:** This refers to the **shoot apical meristem** which is located at the tip of the stem. - **Radical:** This refers to the **root apical meristem** which is located at the tip of the root.