1What does plant survival depend on, similar to animals?
Their ability to respond to changes in the environment
2What type of responses do plants carry out to directional stimuli?
Growth responses
3What is a tropism?
A directional growth response of a plant to a stimulus
4What is phototropism?
A growth response to light
5What is gravitropism?
A growth response to gravity
6What does positive tropism mean?
Growth towards a stimulus
7What does negative tropism mean?
Growth away from a stimulus
8What causes growth responses in plants?
Chemical growth factors released by plant cells
9How do plant growth factors act compared to animals?
They act in a similar way to hormones in animals
10What does it mean that growth factors are specific?
Different growth factors bring about different plant responses
11Where are growth factors often produced in plants?
In the growing parts of plants
12What happens to growth factors after they are produced?
They move to other tissues where they regulate growth in response to a stimulus
13Where is IAA synthesised in plants?
At the tips of roots and shoots
14Where does IAA mainly affect growth?
In the region adjacent to the tip
15What is indoleacetic acid (IAA)?
A plant growth factor
16What group of growth factors does IAA belong to?
Auxins
17How does IAA move between plant cells?
By diffusion and active transport
18How can IAA move over longer distances in plants?
Via the phloem
19How does IAA influence plant growth?
By controlling elongation of plant cells
20What determines the rate of cell elongation in plants?
The concentration of IAA
21What does an uneven concentration of IAA cause?
Uneven growth
22What is gravitropism?
A directional response to gravity
23What is positive gravitropism?
Growth towards gravity
24Where is IAA produced in roots during gravitropism?
In the root tip
25Where does IAA move in a root during gravitropism?
Toward the lower side of the root
26What structure indicates the lower side of the root?
Amyloplasts
27Why do amyloplasts gather at the bottom of root cells?
Because of their density
28What effect does IAA have on root cell elongation?
It inhibits cell elongation
29How does unequal cell elongation cause roots to bend?
Cells on the lower side elongate more slowly than those on the upper side
30What is phototropism?
A directional response to light
31What is positive phototropism?
Growth towards light
32Where is IAA produced in shoots during phototropism?
In the shoot tip
33Where does IAA move in a shoot during phototropism?
Toward the shaded side of the shoot
34What effect does IAA have on shoot cells?
It causes cell elongation
35Why does a shoot bend toward light?
Cells on the shaded side elongate faster than those on the light side
36What effect does IAA have on root cells?
It inhibits elongation
37What effect does IAA have on shoot cells?
It causes elongation
38What are taxes and kineses?
Simple innate responses that help mobile organisms stay in favourable environments
39What stimuli can taxes and kineses respond to?
Light, temperature and humidity
40What are kineses?
Non-directional responses to a stimulus involving random movement
41What is an example of photokinesis?
Flatworms moving faster and changing direction more often in bright light
42Why do flatworms move faster in bright light?
To increase the chance of leaving unfavourable conditions and avoid predation
43What are taxes?
Directional responses to a stimulus involving movement toward or away from it
44What is positive phototaxis?
Movement toward a light source
45Which organism shows positive phototaxis using a flagellum?
Euglena
46Why do Euglena move toward light?
To carry out photosynthesis
47What is an example of positive phototaxis in animals?
Moths moving towards light
48What is an example of negative chemotaxis?
A mosquito moving away from an aerosol spray
49How do kineses differ from taxes?
Kineses are non-directional random movements, while taxes are directional movements toward or away from a stimulus