EduNinjaDescribe the geotropic and phototropic responses of roots and stems.
Which of these is an example of positive phototropism?
a plant root growing away from light
a plant root growing downwards due to gravity
a plant stem growing towards light
a plant stem growing upwards due to gravity
Scientists investigate the effect of salt (NaCl) concentration on the germination of maize seeds.
Batches of seeds are watered with different concentrations of salt solution.
They count the number of seeds that germinate in each batch 12 days after sowing. They then determined the percentage germination.
As plants grow, they produce roots and stems.
Compare the responses of roots and stems to gravity.
Compare the responses of roots and stems to light.
Plants respond to stimuli.
Some of these responses are called tropic responses.
State what is meant by the term tropic response.
Auxin is also involved in a plant's response to gravity.
A student uses this method to study plant responses to gravity.
- put similar plants in three identical pots, A, B and C
- place pot A upright
- place pot B on its side
- place pot C on a device called a clinostat that slowly rotates
- place the pots in evenly illuminated conditions
- leave the pots for six days
The diagram shows the plants after six days.
Pot A
Pot B
Pot C
Explain the differences in appearance of the plants in pots A , B and C after six days.
Use information from the diagram and your own knowledge in your answer.
Describe how the student could modify this experiment to investigate the effect of gravity on plant roots.
The body has a hormonal control system that coordinates some of the body's responses.
Plants also respond to changes in their environment.
Explain how plants benefit from the responses of their roots and stems to the direction of light they receive.