Download Unit 5 Lesson 3

Unit 5
Lesson 3
Understanding Temperature
Effects on Plant growth
Extreme Sport
Extreme Sport
Extreme Sport
Extreme Sport
Extreme Sport
Extreme Sport
Freeze Damage
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Freezing can cause physical damage to the plant cells.
Freeze damage occurs when the cell walls of plants break as the
contents of the cells freeze.
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Hardier plants are better able to withstand low temperatures than
less hardy plants.
Freeze damage is very important to the orchard industries in
agriculture.
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This is especially worrisome with a heavy frost around the time when
fruit trees are in flower.
Flowers can be lost from freezing, and hence an entire crop can be
lost.
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To prevent serious damage to crops, growers may choose to spray their
crops with water as this offers some protection to the flowers, leaves, and
stems.
A continuous application of water prevents the temperature of the plant
tissues from dropping below 32 degrees F.
Freeze Damage
• Landscape plants are also susceptible to freeze damage.
– If soil temperatures drop too low, roots can be killed and the plants will
die.
– Landscape plants often have stems, buds, flowers and leaves that are
marginally hardy to a frost.
– Heavy layers of mulch are often used to help protect delicate landscape
plants from damage.
• Most agricultural crops are herbaceous annual plants and are more
easily damaged by cold temperatures.
• Concern for freeze damage is greatest usually during planting
season
– before plants are well established
– before harvest.
• To assess frost damage, one must be patient!
– It often takes several days to survey the damage and the ability of a
crop to recover from the frost.
Freeze Damage
Frost Damage on Corn
Heat Damage
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The effects of heat damage may not be as evident as that of cold;
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however it can be as detrimental to crop production causing a loss of
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Yields
aesthetic appeal of crops
Heat damage is worst when it is not only hot, but also dry.
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Plants have some ability to cool themselves by transpiration through
their stomata.
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As this water evaporates, it has a cooling effect.
Stomata close if the plant roots cannot supply water quickly enough to
replace water lost from transpiration.
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Further water loss causes wilting
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a drooping condition and a lack of firmness in the plant tissues.
Wilting will result in a loss of turgidity,
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This helps the plant to conserve water.
or water pressure in the plant cells.
Severe heat conditions can cause plant tissues to dry up and die.
Heat Damage
• Excess heat usually causes
scorch symptoms on leaf tips
and interveinal areas.
• Portions of leaves shaded by
other leaves, or leaves on the
shady side of the plant, may
be undamaged.
• Frequently, heat damage will
occur uniformly over all plants
in an affected area