Download Plant Responses to Stimuli

Plant Responses to Stimuli
Tropism – movement toward or away
from a stimuli
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Phototropism – growth
toward light
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Gravitropism – growth
against or with gravity
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Thigmotropism –
growth toward touch
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Plant Hormones – Chemicals that control the
growth, development, and responses to stimuli
Auxin
phototropism
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Gibberelin
growth
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Abscisic Acid
environment stress
Cytokinin
cell division
Ethylene
ripening
Photoperiodisms – the physiological reaction to the
length of day or night. They are sensitive to UV light.
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Long-day plants: will
only flower if the night
is short enough. They
will flower in the late
Spring early Summer.
Short-day plants: Need
a long night to flower.
Day-neutral plants:
These are sensitive to
temperature
Biological Clocks
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Circadian rhythms – (“circa” approximately
“dies” day) physiological cycles based on 24
hour periods.
The leaves of plants will rise and fall every 24
hours, even in constant light or darkness.
Other cycles
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Ultradian cycle - Many in one day. Seconds
to minutes
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Infradian cycle – longer than a day – months
and years
Time Cycles
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Annuals – complete life
cycle in one year (zinnia)
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Biennials –
life cycle in 2 years (foxglove)
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Perennials –
live many years (tulips)