Page 131 - Science Course 1 (Book 1)
P. 131
Mo4-L4a: How Do Plants Respond to Environmental Stimuli?
The number of hours of darkness controls flowering in many plants.
Early Summer Late Fall
Midnight Midnight
6 P.M. 6 A.M. 6 P.M. 6 A.M.
Noon Noon
Long-day Short-day Day-neutral Long-day Short-day Day-neutral
plant plant plant plant plant plant
Flowering Not Flowering Not Flowering Flowering
Flowering Flowering
Short-day Plants Long-day Plants
Critical
Night
Length
Short-day plants flower when a period of Long-day plants flower when a period of
darkness (uninterrupted) exceeds a critical darkness is less than a critical night length
night length threshold
SUMMARY
How Do Plants Respond to Environmental
Stimuli?
Plants respond to stimuli in their environments Photoperiodism occurs in long-day plants and
in many ways. short-day plants. Day- neutral plants are not
affected by the number of hours of darkness.
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