Roland-StoryHigh School

Agriculture Technology Class

Lesson 6.2 --All Wet

Preface:

Water is one of the four major requirements for plant growth and health. Plants, like all living organisms, require water to carry out important metabolic processes. Plants use water for translocation and transpiration. Translocation is the movement of water and dissolved nutrients throughout the plant system. Water carries dissolved nutrients from the roots to the rest of the plant by means of the xylem. Once raw materials are converted by photosynthesis to food sources, the phloem carries these sugars from the leaves to growth and storage areas throughout the plant structure.

Transpiration is the release of water vapor through the plant stomata located in the leaf structure. Transpiration assists in cooling the plant when exposed to hot temperatures and allows the exchange of oxygen and carbon dioxide from the atmosphere. The use of water during transpiration creates a negative osmotic pressure in plants. This pressure difference, called transpiration pull, increases as the temperature increases largely because of a higher rate of photosynthesis and transpiration. As a result, the translocation rate will increase to supply plant parts with enough water.

Concepts:

  1. Different substances that plant containers are made from will affect the rate of water loss by evaporation in potted plants.
  2. Water is used by plants for the translocation of materials within the vascular systems of plants and used to complete the photosynthesis process.
  3. Water is used to help cool the plant during periods of above optimal temperature conditions through the process of transpiration.
  4. Water requirements and tolerances vary among plant species.
  5. The wilting point is a critical physiological stage that if exceeded can cause permanent damage to the health and physical appearance of plants.

Essential Questions:

1. How does the substance a pot is made from influence water loss?

2. How do stomata influence a plant? What is transpiration and why do plants transpire?

3. How do transpiration, evaporation, and runoff differ?

4. What affects the rate of transpiration in plants?

5. How is transpiration related to temperature?

6. What is translocation?

7. How are the xylem and phloem involved in the process of translocation?

8. Why should the wilting of a plant be prevented?

9. How can too much water be harmful to the growing environment of a plant?

10. What determines the water requirements of plants?

11. How is soil moisture monitored to prevent plant wilting?

Key Terms:

Evaporation / Evapotranspiration / Humidity
Osmotic pressure / Phloem / Photosynthesis
Stomata (stomate) / Translocate / Transpiration
Transpiration pull / Turgor / Vascular system
Wilting point / Xylem