5.1.5 Plant Responces Flashcards
What do plants react to?
Chemicals.
Gravity.
Pressure.
Light.
Moisture.
Infection.
Temperature.
Oxygen.
Carbon Dioxide Concentration.
Disease.
Physical Disruption.
Sound.
Touch.
What happens when a plant detects a change?
They pick up electrochemical signals from the environment.
What is a Tropism?
Directional growth response of plants in response to a stimuli.
What is phototropism?
Response to light
What is an example of phototropism?
Plants grow towards the light to maximise photosynthesis.
What is geotropism?
Response to gravity
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What is an example of geotropism?
Roots grow towards the pull of gravity - positive geotropism.
Shoots grow away from the pull of gravity - negative geotropism.
What is chemotropism?
Response to chemicals
What is an example of chemotropism?
Pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertialisation takes place.
What is Thigatropism?
Response to touch
What is an example of thigmatropism?
Climbing plants detect support and wrap around it.
What is hydrotropism?
Responce to water/moisture
What is an example of hydrotropism?
Roots grow towards water
What is a positive tropic responce?
If the plant responds towards the stimulus
What is a negitive tropic responce?
if a plant responds away from a stimulus
What is an advantage of positive and negative tropism?
Roots grow towards gravity - positive geotropism.
Shoots grow away from gravity - negative geotropism.
When is a response not a tropism?
When the response is immediate. As it is not a growth response
What are non directional responses known as?
Nastic responses/movements.
or Trigomonasty
What is the difference between nastic movements and tropisms?
nastic responses are more rapid and are caused by local biochemical signals
What are the plant responces to biotic stresses?
Tannins.
Alkaloids.
Pheromones.
What are tannins?
Chemicals stored within the vacuole. They are fatal to insects and deters herbiovores.
They are toxic and have a bitter taste.
Where are tannins used?
In roots they prevent infiltration by pathogenic microorganisms
What are alkaloids?
Nitrogenous compounds derived from amino acids.
How do alkaloids protect against biotic stress?
Have a bitter taste to deter animals from eating the plant. Some can be toxic.
What is an example of where alkaloids are used?
In growing tips and flowers and peritoneal cell layers of stems and roots.
What are pheromones?
Chemicals released by an individual to affect another
What do pheromones do?
Can control other chemical defenses in plants by switching genes on and off that produce chemicals that deter insects. So they act as hormones
What are examples of the use of pheromones?
Ethene released by plants causes ripening of fruit in nearby plants and causes leaf loss. Oxides of ethene are toxic to insects.
What is a plants responce to freezing?
Some plants produce a chemical that prevents ice crystals forming inside it.
What is a plants response to drought?
Closing stomata or loosing leafs to prevent water loss by transpiration
What are some abiotic stresses experianced by plants?
Freezing.
Drought.
Salinity of soil water.
Presence of heavy metals.
What are plant hormones?
Hormones that act within plants. They work in the same way as animal hormones but are made by cells in a variety of cells rather than specific endocrine glands.
How are hormones moved in plants?
Active transport.
Diffusion.
Mass Flow.
How do hormones interact with the target cell?
The target cell has receptors that are specific to that hormone.
What do cytokinins do?
Promote cell division.
Delay leaf senescence.
Overcome apical dominance.
Promote cell expansion.
What does abscisic acid do?
Inhibit seed germination and growth.
Causes stomatal closure when the plant is stressed by low water availability.
Produced in the roots in response to low water potential and gets translocated to the leaves.
What does auxin do?
Promotes cell elongation.
Inhibits the growth of side shoots.
Inhibits leaf abscission.
What do gibberellins do?
Promote seed germination and growth of stems
What does ethene do?
Promotes fruit ripening
What are deciduous plants?
Plants that loose leaves when very hot or dry (in order to reduce water loss), when the soil water is frozen, or no photosynthesis is taking place.
What is abscission?
The shedding of an old or mature organ from a plant.