plant responses Flashcards
1
Q
abiotic
A
non-living components
2
Q
biotic
A
living components
3
Q
why do plants need to defend themselves?
A
- avoid predation
- avoid abiotic stress
- survive
4
Q
why do plants need to respond to their environment?
A
- to cope with changing environmental conditions
- avoid abiotic stress
- to maximise photosynthesis
- to obtain more, light/water/minerals
- avoid, herbivory
- to ensure, germination / pollination in suitable conditions
- seed dispersal
5
Q
physical plant defences
A
- thorns
- hairy leaves
- leaf folding
- bark
- waxy cuticle
6
Q
chemical responses to herbivory
A
- tannins
- alkaloids
- pheromones
7
Q
Tannins
A
- part of group of compounds called phenols produced by plants.
- make up 50% of the dry weight of leaves.
- found in the upper epidermis of the leaf.
- have a very bitter taste.
- are toxic to microorganisms and insects.
- tannins bind to digestive enzymes produced in the saliva and inactivate them.
- tea and red wine are rich in plant tannins.
- in some herbivores (e.g. cattle, sheep) they can bind to proteins in the gut, making the plant hard to digest.
8
Q
Alkaloids
A
- large group of compounds derived from amino acids.
- very bitter tasting.
- these are chemicals with bitter tastes, noxious smells or poisonous characteristics that deter or kill herbivores, e.g. tobacco plants produce the alkaloid nicotine in response to tissue damage. nicotine it highly poisonous to many insects.
- many act as drugs which affect metabolism of the animals that injests it, sometimes poisoning them.
- they are located in growing tips and flowers, and peripheral cell layers of stems and roots.
9
Q
chemical defences against herbivores: Pheromones
A
- pheromones are chamicals which are released by one individual, which can affect the behaviour and physiology of another member of the same species.
- the chemicals are capable f acting like hormones outside of the body of the secreting individual.
- there are alarm pheromones, food trail pheromones, sex pheromones, trail pheromones and many others that affect behaviour or physiology.
10
Q
pheromones example
A
- maple trees release a pheromone in response to being attacked by insects. - - - this pheromone is absorbed by leaves on other branches.
- these leaves then make chemicals to help protect them if they are attacked.
- it has been observed that leaves on nearby trees also prepare for attack in response to the pheromones.
11
Q
responses to abiotic stress
A
- abiotic stress for plants can occur in various forms, including:
- freezing
- drought
- increased soil water salinity
- presence of heavy metals
- plants can responf to drought by shutting their stomata (reducing water loss through transpiration) or by dropping their leaves.
- some plants can respond to temperatures below freezing by producing antifreeze chemical in their cells that decreases the formation of ice crystals. that can destroy plant cells if allowd to form within them.
12
Q
nastic responses
A
a non-directional response to stimuli, e.g. thigmonasty. e.g. mimosa pundicaplant responds to touch by folding its leaves.
13
Q
plant tropisms
A
a tropism is a directional growth response in which the direction of the response is determined by the direction of the external stimulus.
14
Q
positive tropism
A
a growth response towards the stimulus e.g. light
15
Q
negative tropism
A
a growth response away from the stimulus e.g. gravity
