Plant Biology and Production

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Plant Biology and Production
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Unit 4

• Environmental Factors Effecting Plant Growth

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Determining the Influence ofTemperature on Plants

• Lesson 2

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Interest Approach

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

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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?

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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.

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Terms

• Cool season crops
• Hardiness
• Growing degree day (GDD)
• Metabolism
• Plant heat-zone map
• Plant hardiness zone map

• Stratification
• Thermoperiod
• Thermoperiodic
• Vernalization
• Warm season crops

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How does temperature affect plant growth?
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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.

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How does temperature affect plant growth?

• Cool or cold temperatures slow metabolic
  processes, while warmer temperatures speed the
  processes.

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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.

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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.

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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 86F.
• During hot summer days plants draw upon stored
  energy reserves.

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What are some plant responses to temperature?
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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.

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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.

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Thermoperiodic Plants

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

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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.

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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.

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Warm season crops

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

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Vernalization

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

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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 32F and 45F to break their
  rest period.

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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.

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What is hardiness?
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Hardiness

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

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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.

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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.

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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 86F.

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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.

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What is a growing degree day?
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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.

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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 50F or
  below.

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Growing degree days (GDD)

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

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Growing degree days (GDD)

• Example If a low temperature was 60F and the
  high was 90F, the GDD would be 60 86 146
  divided by 2 73 50 23 GDD.

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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.

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Review

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