Plant Biology and Production

1. Plant Biology and Production

2. Unit 4 Environmental Factors Effecting Plant Growth

3. Determining the Influence ofTemperature on Plants Lesson 2

4. Interest Approach • I would like to grow bananas so I can have fresh bananas throughout the year.

5. Interest Approach • Is there anything wrong with this idea? • Is our soil not the right type? • Is the air not appropriate? • Do we not get enough rain? • Is our temperature a problem? • How have plants become adapted to different temperature ranges?

6. Student Learning Objectives • 1. Discuss the effect of temperature on plant growth. • 2. Describe plant responses to temperature. • 3. Explain hardiness. • 4. Explain growing degree days.

7. Cool season crops Hardiness Growing degree day (GDD) Metabolism Plant heat-zone map Plant hardiness zone map Stratification Thermoperiod Thermoperiodic Vernalization Warm season crops Terms

8. How does temperature affect plant growth?

9. How does temperature affect plant growth? • A. All of the chemical reactions in a plant, including photosynthesis and respiration, fall under a term, metabolism. • The speed at which metabolism occurs is affected by temperature. • This is because the enzymes that drive the reactions are sensitive to temperature.

10. How does temperature affect plant growth? • Cool or cold temperatures slow metabolic processes, while warmer temperatures speed the processes.

11. How does temperature affect plant growth? • B. Most plants show optimum growth when night temperatures are 10 to 15 degrees cooler than day temperatures. • Under ideal conditions photosynthesis occurs at a high rate during the day. • The cooler temperatures at night slow respiration.

12. How does temperature affect plant growth? • For growth to occur, the rate of photosynthesis must exceed that of respiration. • High temperatures can speed the rate of respiration beyond that of photosynthesis.

14. How does temperature affect plant growth? • The products of photosynthesis are used more rapidly than they are produced. • In many plants, photosynthesis shuts down at temperatures above 86°F. • During hot summer days plants draw upon stored energy reserves.

15. What are some plant responses to temperature?

16. What are some plant responses to temperature? • II. Different species of plants respond differently to temperature. • Temperatures also play a role in different plants functions.

17. Thermoperiodic Plants • A. The change of daily temperatures is called thermoperiod. • When changes in daily temperatures influence plant responses, such as flowering, the plants are said to be thermoperiodic.

18. Thermoperiodic Plants • Poinsettias and chrysanthemums are thermoperiodic plants. • They initiate flowers when temperatures become cooler and days grow shorter.

19. Cool Season Crops • B. Wheat, oats, barley, rye, spinach, and lettuce are cool season crops meaning they prefer cooler growing temperatures and are tolerant of frost. • When temperatures rise in combination with longer days, spinach and lettuce initiate flower production.

20. Warm season crops • Warm season crops require warmer temperatures for best growth. • Cotton, corn, soybeans, and sorghum are an example of a warm season crop.

21. Warm season crops • Another warm season crop, tomatoes, will not flower if temperatures are cool.

22. Vernalization • C. Some plants require a cold treatment for physiological processes to occur. • This is known as vernalization.

23. Vernalization • Tulips and narcissus require vernalization to flower. • Some cereal grains, including winter wheat, also require vernalization. • Apples require 1,000 to 1,200 hours of temperatures between 32°F and 45°F to break their rest period.

24. Stratification • D. Seeds of some plants have a dormancy mechanism that is broken by a cold period. • The seeds do not germinate until the seed has undergone a cold period. • This cold requirement for seeds is known as stratification.

25. What is hardiness?

26. Hardiness • III. Plants can be classified as hardy or non-hardy depending on their ability to withstand cold temperatures. • Hardiness is a plant’s ability to tolerate cold temperatures.

27. Plant hardiness zone map • A. The USDA has established a plant hardiness zone map for the United States, that reflects the average minimum winter temperatures for given areas. • The map shows eleven zones of temperatures. • It is valuable in selecting plants adapted for growing in those areas.

29. Plant heat-zone map • B. Heat also plays a role in the performance of plant species. • Some plants are more sensitive to heat than others. • The plant heat-zone map has been developed by the American Horticultural Society to help identify areas in which landscape plants can flourish.

30. Plant heat-zone map • The map shows 12 zones. • Each zone reflects a rating of summer heat based on the average number of days above 86°F.

31. Plant heat-zone map • Eighty-six degrees is a temperature at which plants are unable to process water fast enough to maintain normal functions. • Plants also experience damage to cellular proteins.

33. What is a growing degree day?

34. Growing degree days (GDD) • IV. Growing degree days (GDD) is a measure of temperature requirements for plants and can be used to estimate growth and development. • A. The basic concept of growing degree days is that plant development will occur when temperatures exceed a base temperature.

35. Growing degree days (GDD) • For corn, the maximum temperature plus the minimum temperature in a day divided by 2 minus 50. • Fifty is selected as the constant because corn grows very little at temperatures of 50°F or below.

36. Growing degree days (GDD) • Growth is also checked when temperatures rise above 86°F, so all temperatures recorded above 86°F are counted as 86 in the formula. • Most corn hybrids have fairly specific GDD specifications.

37. Growing degree days (GDD) • Example: If a low temperature was 60°F and the high was 90°F, the GDD would be 60 + 86 = 146 divided by 2 = 73 – 50 = 23 GDD.

38. Growing degree days (GDD) • The GDD are added during the growing season. • If a variety of corn required 2,450 GDD, it would require 107 days to maturity using the figure calculated in the example.

39. Review • Discuss the effect of temperature on plant growth. • Describe plant responses to temperature. • Explain hardiness. • Explain growing degree days.