1. Roots
Section 23.2

2. What are the two different types of root systems?
Taproots – Primary roots grows long, thin and thick
Gives rise to smaller branch roots
In some cases, such as oak and hickory trees – grow so large they can reach water several meters down
Carrots, dandelions and beets – all examples of short taproots that store sugars and starches
Fibrous root systems - many equally sized branch roots
All grow separately from the base of the stem
No single root grows larger than the rest
Help prevent soil erosion

3. Anatomy of a root
Roots contain, dermal (epidermis), vascular and ground tissues
Key role in water and mineral transport
Epidermis – protection and absorption
Covered with root hairs that produce large surface area – maximizing efficiency
Ground tissue – Cortex
Material flows through the cortex and acts as storage area for products of photosynthesis
Endodermis encloses vascular cylinder
Vascular tissue – enclosed in vascular cylinder
Apical meristem – produce new cells near root tip, causing roots to grow
Protected by root cap
Cap also secretes slippery substance easing progress through the soil
Cap cells constantly destroyed and replaced

4. What are the main functions of a root?
Roots support a plant, anchor it to the ground, store food, and absorb water and dissolved nutrients from the soil
Uptake of nutrients
Soil can vary a lot from place to place – texture and composition
Determine which kinds of plants can grow in the soil
Plants require a lot of different nutrients
Main ones are Nitrogen, Phosphorus, Potassium, Magnesium and Calcium
Alongside trace elements
Possible to have too much of a good thing!

5. What nutrients does a plant need?

6. Root functions continued…
Active transport of dissolved nutrients
Cell membranes of root hairs and other epidermis cells contain active transport proteins
Energy required to move particles against a concentration gradient across a membrane
Osmosis
Due to accumulation of nutrients, water will follow nutrients into the roots
Although water is not pumped, it will accumulate
Movement into vascular cylinder
Water and minerals pass the inner boundary of the cortex and move towards the vascular cylinder
Endodermis encloses vascular cylinder
Caspian strip – waxy layer that surrounds vascular tissue
Forces water and minerals to pass through cell membrane of endodermis
Endodermis cells can filter and control the water and dissolved nutrients that enter vascular cylinder
Ensure that nutrients do not leak back out
Results in one way passage

7. Root pressure explained
The one way system in plants is very important
Allows plants to generate enough pressure to move water out of the soil and into the body of the plant
As water is contained by Caspian strip – the only way it can go is up!
But, this is just the beginning….

8. Key points questions What are the main functions of a root?
How are tissues distributed in a plant root?
How is osmosis involved in the the absorption of water and minerals?
What is the Caspian strip? What role does it play in water transport? Why is this so important?