Unit 4: Agricultural Botany

Module 1: Plant Structure, Function and Growth

Learning Objectives: 1.7, 1.8

Lesson 1: The Leaf, Stem, and Root

Lesson Objectives:

  • To study the three major structures of a plant which include the root, stem and leaf along with their locations and functions.
  • To identify the major tissue areas found in a plant.

Evaluation:

  • Activity: Structure and Function of the Leaf
  • Activity: Structure and Function of the Stem
  • Activity: Structure and Function of the Root

Major Plant Organs and Their Functions

1. The Leaf

The leaf of a plant serves two basic functions: i) photosynthesis, and ii) cellular respiration.

i) Photosynthesis

Photosynthesis is a chemical reaction in which plants convert radiant energy (light energy) into chemical energy (food energy or more specifically, glucose).

STOP

&

THINK

Can you list the reactants and products for the process of photosynthesis? In other words, what is needed for the reaction to take place, and what is produced as a result of the reaction?

ii) Cellular Respiration

Cellular respiration is the chemical reaction in which chemical energy (glucose) is converted into usable energy for the plant.

Activity: Structure and Function of the Leaf

By completing the activity below, you will learn about the different cells and tissue types that make up the main structure of the leaf.

1. Diagram and label the cross section of a typical leaf, and describe the function of each of the structures that you label.

Note: If the required materials are not available, you may view an image of a typical leaf cross section at the link below.

Plants cross sections

2.      Sketch a diagram of a 'stomate' and describe how a stomate functions. Why might the ability of the stomate to close be beneficial to the plant?

3.      Many leaves are covered in tiny hairs called tricomes. What purpose might these tricomes serve?


2.      The Stem

The stem plants exist in a variety of sizes and forms. However, all stems provide a few important functions:

  • i) provide support for the plant
  • ii) provide transportation between roots and leaves
  • iii) act as a site for food storage

Activity: Structure and Function of the Stem

1.      Listed below are the main tissue types found in both monocot and dicot stems. Describe the location and function of each of the tissues.

  • epidermis
  • cortex
  • pith
  • Vascular Tissue (vascular bundle includes two tissue types)
    • xylem
    • phloem

2.      Use a prepared slide and a compound microscope to view a cross section (x.s) of a monocot stem. Note the arrangement of vascular bundles, which distinguishes it from a dicot stem. Corn, Zea mays, is commonly used to produce stem cross sections.

Produce a diagram of the stem cross section and label each of the tissues from question #1 above. You may need to use a textbook diagram to assist you with the identification of the different tissue types.

Note: If the required materials are not available, you may view an image of a monocot stem x.s at the link below.

Plants cross sections

3.      Use a prepared slide and a compound microscope to view a cross section (x.s) of a dicot stem. Note the arrangement of vascular bundles which distinguish it from a monocot stem. Alfalfa, Medicago sativa is commonly used to produce stem cross sections.

Produce a diagram of the stem cross section and label each of the tissues from question #1 above. You may need to use a textbook diagram to assist you with the identification of the different tissue types.

Note: If the required materials are not available, you may view an image of a dicot stem cross section at the link below.)

Plants cross sections

4.      Recall from are previous study of the angiosperms that there are two types of plant stems, herbaceous stems and woody stems. Describe the differences between these two stems after the first year of growth.


3.      The Root

The roots of a plant serve three important functions:

  • i) anchor the plant
  • ii) absorb water and mineral from the soil
  • iii) act as a site for food storage

Activity: Structure and Functions of the Root

1.      The root contains many of the same tissue types and functions that are found in the stem. Describe the location and function of the following additional tissues found in the root of the plant.

  • cortex
  • pericycle
  • cambium

2. Use a prepared slide and a compound microscope to view a cross section (x.s) of a root . Produce a diagram of the root cross section and label the epidermis, cortex, endodermis, pericycle, xylem and phloem. You may need to use a textbook diagram to assist you with the identification of the different tissue types.

Note: If the required materials are not available, you may view an image of a root at the link below.

Plants cross sections

3. What purpose do root hairs serve?

4. Recall from your previous studies that there are two main types of roots, tap-roots and fibrous roots. Describe the differences in growth of these two types of roots and provide common examples of each type.

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