Responses [5] Flashcards
What is a tropism?
How plants respond to a directional stimulus
Tropism Categories?
Tropism can be positive (Move towards) or negative (Move away from)
Examples include geotropism, phototropism, hydrotropism, chemotropism and thigmotropism (touch)
What is an Indoleacetic Acid (IAA)?
IAA is a plant hormone that stimulates cell elongation, and is moved around the plant to the shaded areas.
It STIMULATES growth in shoots and INHIBITS growth in roots. It is a type of auxin.
What is an alkaloid?
A bitter, noxious, poisonous compound released from tissues in response to herbivory.
Nicotine is an example of an alkaloid that is released from tobacco plants.
What are pheromones?
A chemical that produces a response in other organisms, usually drawing predators towards the plant in response to herbivory.
When corn plants are eaten by caterpillars, they releases pheromones for parasitic wasps.
What are tannins?
A bitter-tasting chemical that reduces herbivory through poor flavour
Auxin function
- Control Apical Dominance (Auxin’s in shoot inhibit lateral side shoots)
- Inhibits Abscission
- Controls growth in response to tropisms
Ethene Function
- Triggers fruit ripening
- Stimulates Abscission (Triggered by shortening day length)
Gibberellin Function
- Triggers stem elongation
- Stimulates seed germination
(Released from embryo and causes the aleurone layer to release amylase, which breaks glucose into maltose for seed growth).
» Triggered by increasing water/light levels
Abscisic acid function
- Inhibits seed germination
- Regulates stomatal closure
(Low water causes binding to guard cells and opening of K⁺ channels. K⁺ move out of cell, lowering WP and going flaccid)
Ethene commercial use?
For fruit ripening
- Breaks down chlorophyll, cell walls and converts starch to sugar
IAA commercial use?
Low levels of IAA can be used as a rooting powder, causing a plant cutting to rapidly grow new roots.
High levels of IAA can be used as a selective weed-killer. It causes broad-leaved plants like dandelions to grow rapidly, exhausting themselves to death
Nervous system categories
Central - Brain & Spinal Cord
Peripheral - All others
Sympathetic - Body becomes stimulated
Parasympathetic - Body becomes relaxed
Autonomic - Unconscious control
Somatic - Conscious control
What is the hypothalamus?
Found beneath the middle of the brain
- Maintains body temp and homeostasis
- Controls pituitary gland
What is the pituitary gland?
Found beneath the hypothalamus
- Releases master hormones that stimulate other glands
Posterior - ADH
Anterior - ACTH
What is the cerebrum?
Largest part, synonymous with cortex
- Involved in hearing, vision, thinking & learning
What is the cerebellum?
Found beneath the cerebrum at the rear
- Controls muscle co-ordination, posture and balance
What is the medulla oblongata?
At the top of the brain stem
- Controls automatic breathing and heart rate
