Plants (Tropism) Flashcards
What is the survival of plants dependent on?
Their ability to respond to changes in their environment
How do some plants defend against herbivore damage?
By producing poisonous substances
Why do trees in forests grow very tall?
To reach a light source
What adaptation do some flowers have to reduce water loss?
They can close up at night
Do plants possess a nervous system?
No
What type of growth responses occur due to uneven growth?
Responses that involve plants growing against gravity or towards light
What is the term for the growth response of a seedling bending towards light?
Tropism
What is phototropism?
A growth response to light
What is gravitropism?
A growth response to gravity
What can tropisms cause plants to do?
Grow towards or away from the stimulus
What do plants rely on for growth responses?
Chemical substances released in response to a stimulus
How do specific growth factors in plants compare to hormones in animals?
They act in a similar way
How quickly do phototropic responses occur in plant shoots?
Within minutes of being exposed to light
Where do specific growth factors move in flowering plants?
From the growing regions to other tissues
What was the first specific growth factor discovered in plants?
Indoleacetic acid (IAA)
Where is IAA synthesized in plants?
At the tips of roots and shoots
What does IAA mainly affect?
The elongating region of a plant
What happens when IAA binds to protein receptors on cell membranes?
It lowers the pH by releasing hydrogen bonds
What effect does a lowered pH have on cellulose cell walls?
It breaks some of the bonds between the microfibrils
What does the loosening of cell walls allow?
Cells to be more easily stretched when turgor increases
How does IAA influence plant growth towards a stimulus?
By affecting cell elongation
What is an example of phototropism in plants?
The parsley plant growing towards the light source
