CH28: External factors Flashcards
Phototopism of a shoot is caused by ____ of cell ____ on the shaded side of the tip.
stimulation; elongation
The statoliths in roots and stems are:
amyloplasts
Thigmotropism is the response to:
contact with a solid
A plant’s photoperiodic response depends on ____.
Temperature
The number of required _____ cycles varies with the species.
induction
Some plant spacies can measure period durations of only ____ minutes
20 minutes
The plant’s photoperiodic response may vary with ____.
Age
Lettuce seeds will germinate if exposed to:
red light followed by far-red light followed by red light
Phytochrome can be detected only with a ______ __________.
sensitive spectrophotometer
Maryland mammoth tobacco flowers in the field by:
covering the plants in the afternoon to produce short days
To induce germination, some seeds are soaked in alcohol in order to:
remove substances that impede the entry of water
In the potato, bud dormancy is broken by:
dry storage
Thigmonastic movements are responses to:
marchanical stimulation
Define tropism
A growth response involving bending or curving of a plant part toward or away from an external stimulus that determines the direction of movement.
Define phototropism
Curving or growing shoot tips toward light
What hormone is involved in phototropism?
Auxin
What wavelength triggers phototropic respnonse?
blue wavelengths (400-500 nanometers)
What mediates the redistribution of auxin in response to light?
A photoreceptor
What is a photoreceptor?
A pigment-containing protein that absorbs light and converts the signal into a biochemical response
Define gravitropism
Response to gravity
Define positive gravitropism
If seedling placed on side, root will grow downward (with gravity)
Define negaitve gravitropism
If a seedling is placed on side, shoot will grow upward (against gravity)
How many hours do circadian rhythms tend to be on?
24
What type of plant grows mostly in the summer?
Long-day
What type of plant grows during the early spring?
Short-day
Define etiolation
Prolonged growth in the absence of light in search of light
- often leads to lack of pigment
Define thigmonastic
A response to a stimulus (not really directionally)
Heliotropism
Solar tracking
Thigmo-morphogenesis movement
Growing away from a stimulus (dog rubs agsinst it every time it walks by)
