Plant Responses Flashcards
What is stimulus and response?
A stimulus is somthing that causes a reaction in an organism or in part of an organism
A response the the activity of a cell, organism or part of an organism in reaction to a stimulus
Structures needed for response:
- A chemical or hormonal system
- Sense organs and a nervous system
- Ability to move and grow, plants move by growing slowly in particular direction
- An immune system that allows organisms to respond to infection
What are the responses in flowering plants?
Respond by a combination of internal and external factors
Normally external factors stimulate the production of internal factors called growth regulators
External factors:
- light intensity( shoots grow twords light)
- Day length (changes in day length cause flowering, seed and fruit formation)
- Gravity ( Shoots grow away from gravity, roots grow twords gravity)
- Temperature ( enzymes respond to changes in temperature that in turn affect rate of growth)
Internal factors (Stimuli) :
- main internal factors are growth regulators
- Produced in the growing tips (meristems) of roots and shoots
What are topisms? 🌱
A tropism is the change in growth of a plant in response to an external stimulus
Positive topisms occur when the plant growth in the direction of the stimulus
Negative topisms occur when plants grow away from the stimulus
The advantage of topisms is that they allow the plant to obtain better growing conditions
What is phototropism? ☉🌿
Phototropism is the change in growth of a plant in response to light from a given direction
The shoots of a plant are positively phototropic ie: they grow twords the light
The roots are negatively phototropic ie: they grow away from light allowing them to grow into soil
What is geotropism? 🏔🌲
Geotropism is the change in growth of a plant in response to gravity
The shoots are negatively geotrophic allowing them to grow away from gravity and up twords the light
The roots are positively geotropic causing them to grow down into the soil to improve anchorage and absorption
What are growth regulators?
Growth regulators are chemicals that control the growth of plants
Produced in the meristems and carried to the site of action in the vascular system
Similar to the way in humans hormones are produced in one location but carried in the blood to where they act
Growth regulators are often compare to hormones
It is difficult to identify the precise function of growth regulators for the following reasons:
- They are active in tiny amounts
- They have different effects depending on concentrations
- They have different effects depending on where they act
- They interact with each other, may increase the effect but can also cancel each other out decreasing effect
What are growth regulators?
Growth regulators are chemicals that control the growth of plants
Produced in the meristems and carried to the site of action in the vascular system
Similar to the way in humans hormones are produced in one location but carried in the blood to where they act
Growth regulators are often compare to hormones
It is difficult to identify the precise function of growth regulators for the following reasons:
- They are active in tiny amounts
- They have different effects depending on concentrations
- They have different effects depending on where they act
- They interact with each other, may increase the effect but can also cancel each other out decreasing effect
What are growth inhibitors and promoters?
Growth inhibitors reduce the growth of plants
- Abscisic acid (ABA) inhibits growth in seeds
- ethene is a gas that inhibits growth in petioles, results in leaf fall in autumn
Growth promoters increase the growth of plants eg: IAA
