tropisms Flashcards
What is a tropism?
A directional growth response to a stimulus
How are taxis and tropisms similar?
They are both directional
How are taxis and tropisms different?
Taxis is a response using movement, and tropism is growth
Plant shoots are negatively gravitropic, what does this mean?
They grow against/away from the pull of gravity
What part of a plant produces growth factors such as auxin?
he meristem – growing tips in roots and shoots
How do plant growth factors such as auxins affect plant growth?
They are produced in the meristem tissue and diffuse back from the growing tip and increase plant growth of shoots by making cell walls stretchy so the cells can become longer (elongate). It inhibits elongation of root cells.
What is indoleacetic acid (IAA)?
An important growth factor, a type of auxin, produced in the growing tips of roots and shoots in flowering plants.
. How is IAA moved from the tips to other tissues?
diffusion
How does the distribution of IAA affect the growth of shoots in response to light?
The IAA moves to shaded parts of the shoot and elongates cells there, causing uneven growth and bending towards the light
How does the distribution of IAA affect the growth of roots in response to gravity
IAA moves to the lower side of the root and inhibits growth there, causing uneven growth bending downwards
Why is gravitropism important for newly planted seeds in the soil?
It ensures shoots grow upwards towards light (by being negatively gravitropic) and roots grown downwards (positively gravitropic).
why is phototropism important for plants?
It ensures shoots grow towards light to maximise light absorption for photosynthesis.
