Plant and animal responses. Flashcards
Name the 3 chemical defences in plants
- Tannins
- Alkaloids
- Pheromones
What is meant by a tropism?
A directional growth response of plants
What are tannins, where are they found and what do they do?
- Chemicals toxic to micro-organisms and larger herbivores.
- They are found in the upper epidermis
- They impact herbivore digestion
- They prevent infiltration in roots
What are alkaloids, where are they located and what do they do?
- Chemical defences that are derived from amino acids
- Located in growing tips and flowers as well as peripheral layers (stem and roots)
- Act as a feeding deterrent by making plants taste bitter
What are pheromones?
Chemicals released by one individual plant that can affect the behaviour and physiology of another.
What is meant by tropism?
A directional growth response towards or away from a stimulus
Name 4 different tropisms?
- Phototropism
- Geotropism
- Chemotropism
- Thigmotropism
Are shoots negatively or positively phototropic
Positively phototropic
Are roots positively or negatively phototropic?
Negatively phototropic
Are roots positively or negatively geotropic?
Positively gravitropic (they grow with the pull of gravity)
What is meant by chemotropism and give an example
- Growth towards/away from chemical stimulus
- On a flower, pollen tubes grow down the style, attracted by chemicals towards the ovary for fertilisation
What is meant by thigmotropism and what is an example?
Directional response towards physical contact.
Shoots of climbing plants (such as ivy) wind around other plants or structures to gain support.
What decides whether a plant is positively tropic or negatively tropic?
- If a plant responds towards a stimulus it is positively tropic
- If a plant responds away from a stimulus it is negatively tropic
What is a non-directional plant response called?
Nastic response/movement
What plant exhibits a nastic movement
Mimosa pudica
