There are two main types of root systems: taproot systems and fibrous root systems. A taproot system features a primary taproot that grows downward deep into the soil, with many smaller secondary roots branching out from it. A fibrous root system lacks a dominant taproot and instead comprises many similar-sized primary and secondary roots that spread close to the soil surface. Roots have several key functions: to absorb water and minerals, anchor the plant, and store food produced by the leaves. The root tip contains cells called the apical meristem where new cells are produced, and is protected by the root cap. [END SUMMARY]

1. LESSON 2 Understanding Root Anatomy

2. Vocabulary Apical meristem Epidermis Fibrous root system Primary root Root cap Root hairs Secondary roots Taproot system

3. What Are the Functions of a Plant’s Roots? A plant’s health is directly related to its roots Weak and diseased roots decrease a plant’s health Roots need to continuously grow in order to stay healthy This is why plants become pot-bound: the roots start growing out of the pot because it is too small A pot bound plant in need of transplanting Courtesy of Delmar Publishing

4. Functions of a Root System 1. Absorb water and minerals from the environment 2. Anchor the plant in the ground 3. Store food that has been made in the leaves by photosynthesis Can be used later by the plant to grow and survive Taraxacum officinale – the common dandelion Courtesy of Wm. C. Brown Publishers

5. What Are the Parts of a Root? When a seed germinates, the first structure to appear is the root, or radicle A. It becomes the primary root Usually the most important root in some plants B. Other roots branch out from the primary root; called secondary roots Cotyledon Radicle = Primary root; notice all the root hairs Courtesy of McGraw Hill

6. C. The apical meristem , found at the root tip, is where new cells develop It is covered by the root cap – protects it from damage as it passes through coarse soil particles Epidermis Vascular cylinder (xylem & phloem) Cortex (food storage ) Root Cap Apical meristem Courtesy of Dorling Kindersley, Inc .

7. D. The surface of the root is protected by skin cells called the epidermis Where water and minerals enter the root by osmosis & diffusion Can grow long, hair like projections called root hairs They greatly increase the surface area of the root to allow more water intake Epidermis Courtesy of Delmar Publishing

8. Regions of Cell Development Notice that cell division occurs at the tip of the root Older cells are found farther away from the root tip Root Cap Region of Cell Division Region of Elongation Region of Maturation Apical meristem Courtesy of McGraw Hill Publishers

9. There are several other layers of cells found within the root A. Cortex – this is where the root stores the food produced by the leaves; it is made out of parenchyma tissue B. Endodermis – the inner boundary of the cortex; one cell layer thick; controls the movement of water and minerals into the xylem and phloem C. Pericycle – a layer found inside the endodermis which may produce lateral roots; also produces vascular cambium in dicots

10. D. Vascular cylinder , or stele – forms the central cylinder of the root; it is made out of two secondary transport tissues 1. Xylem – carries the water taken in by the root hairs and epidermis up the plant to the stems and leaves 2. Phloem – carries the food produced by the leaves down to the roots to be stored in the cortex

11. Internal Layers of the Root Lateral Root Xylem Phloem Pericycle Endodermis Cortex Root Hairs Vascular Cylinder

12. What Are the Two Types of Root Systems? Plant root systems are organized in two basic ways; It has to do with primary and secondary roots A. A root system comprising one main primary root and many secondary roots branching off the primary root is called a taproot system Ex. Carrot, Parsnip, Oak Their roots reach far into the ground; they can be several feet long

13. Examples of Taproots Carrot Beet Sweet potato Courtesy of Wm. C. Brown Publishers

14. B. A system which has no dominant primary root but is made of many primary and secondary roots of similar size is called a fibrous root system Ex. Grasses, Magnolia, Rhododendron, Euonymus The roots are smaller, shorter and more compact; They usually never grow below the first 6-12 inches of soil These roots form a large network underground Fibrous root system of grass Courtesy of McGraw Hill Publishing

15. What Does a Healthy Root System Look Like? A healthy root system is white or nearly white in color and smells fresh, or earthy If roots are black, brown, or dark orange and smell rotten or sour, the root system is having some problems Watering a plant properly is one of the most important ways to keep the root system healthy

16. If the plants are grown in pots, be sure that there are drainage holes in the bottom to allow excess water to drain Soak the pot until the growing medium is saturated and water drips out of the drainage holes This encourages the roots to grow through the entire pot Allow the pot to dry out slightly between watering Watering too frequently is a common cause of root death Medium that is kept wet has limited air exchange; the root tissues die for lack of air.

17. Summary What are the three functions of a root? What is another name for a primary root? In the tip of the root, what kinds of cells are the only ones that divide? What is the epidermis and what is its function? Where do root hairs grow from?

18. Summary Why does a plant have to have numerous root hairs instead of just two or three? Pretend you are a water molecule and you need to get into the center of the root. What are all the layers you must go through before reaching the center? Describe the functions of the xylem and phloem. Where is food stored in the root?