Text C Biology 9.4 Plant Control Systems Flashcards
(63 cards)
What is the term for environmental factors that cause reactions in organisms?
Stimuli
The singular form is ‘stimulus’.
What is phototropism?
The growth of a plant toward a light source
Phototropism helps maximize light absorption for photosynthesis.
Tropism =
1899, “tendency of an animal or plant to turn or move in response to a stimulus,” 1899, abstracted from geotropism or heliotropism, with the second element taken in an absolute sense; ultimately from Greek tropos “a turning” (from PIE root *trep- “to turn”).
How do plants bend and grow toward light?
By growing cells on one side of the stem more elongated than on the other side
This uneven growth causes the stem to curve toward the light.
What happens to the leaves of beans and other plants over the course of a day?
They change position, raising to a horizontal position in the morning and dropping to a vertical position in the evening
These movements are controlled by changes in turgor pressure in cells at the base of the leaves.
What is the benefit of phototropism for plants?
Maximizes the amount of light absorbed by the plant’s leaves
Increased light absorption enhances photosynthesis, fueling further growth.
Fill in the blank: The movement of matter in living systems includes transport at the level of the _______.
cell
True or False: Plants can move their entire bodies like animals.
False
Plants have control systems that allow them to respond to environmental changes but do not move from one location to another.
What are the responses called that make up plant control systems?
Tropisms
What controls the sleep movements of plant leaves?
Changes in turgor pressure in cells at the base of the leaves
What did Boysen-Jensen find about the signal produced by the tips of seedlings?
The signal could pass through gelatin but was blocked by mica.
What is phototropism?
Phototropism is the growth of plant cells in response to light, causing some cells to elongate.
What changes occur in the cell walls and vacuoles during phototropism?
Major changes occur that are particularly important for cell growth.
Who concluded that the tip of the seedling detects light?
Charles and Francis Darwin.
What did the Darwins speculate about the signal from the plant tip?
They speculated that a signal was sent downward from the plant tip.
What did Boysen-Jensen use to test the Darwins’ idea?
He cut away the tip of a seedling and placed a block of gelatin on the cut end.
What was the outcome when seedlings were treated with gelatin?
The seedlings behaved normally and bent toward the light.
What happened to seedlings treated with mica?
They did not respond to the light and grew straight up.
What did Frits Went confirm about plant growth chemicals?
He confirmed that a growth chemical is produced in the plant tips.
What is auxin?
Auxin is a growth chemical produced in the tips of plants.
What did Went do to extract the growth chemical?
He removed the tips from young stems and placed them on a block of agar.
What was observed when agar containing auxin was placed on one side of a cut stem?
The plant stem curved away from the side on which the agar was placed.
What was the control used by Went in his experiment?
Squares of agar that did not contain any extract from the plant tips.
What did Went conclude from his experiments?
A chemical produced in the plant tips stimulates growth.
Fill in the blank: The type of plant response to touch is called an _______.
anastic response.
