Response Flashcards
5 things animals respond to
light sound hunger pain presence of foreign cells
3 ways in which animals respond
movement
production of chemicals (enzymes, hormones)
production of cells eg. lymphohocytes
4 things that animals need to carry out a response
sense organs and a nervous system
hormonal system
muscular and skeletal system
immune system
5 stimuli that plants respond to
light, gravity, touch, H2O or chemicals
2 ways in which plants respond
changing their pattern of growth (growth regulation)
germinating, flowering, becoming dormant
what are plant responses due to?
the action of chemicals called growth regulators
speed of plant responses
much slower than animal responses
4 external factors that regulate the growth in plants
light intensity
day length
gravity
temperature
how does light intensity act as a growth regulator
affects the rate of photosynthesis and growth
how does day light act as a growth regulator
it varies with the seasons, has major effects on seed germination, flowering, seed dormancy and leaf fall
how does gravity act as a growth regulator
it ensures that roots grow downwards and shoots grow upwards
how does temperature act as a growth regulator
heat (high temperatures) promotes growth by increasing the rate of enzyme activity
main internal factor of growth regulation in plants
the production of chemicals called growth regulators in the meristems
Growth regulators
chemicals produced by a plant that control its growth and development
how do growth regulators get to where they need to be
they are produced in one part of the plant eg. meristems and they are transported to another part of the plant where they cause a response in vascular tissues
comment on the speed of growth regulators
slow acting but with a long-lasting effect
what does their effect depend on?
their concentration and the location in the plant in which they act
higher concentration of auxin
stimulate growth in shoots and inhibit growth in roots
lower concentration of auxin
cause more growth in rots and no effect on shoot growth
how do growth regulators interact with each other and give an example
interact with each other in controlling growth and development eg. auxins and gibberellins together promote cell elongation in stem
5 commercial uses of plant regulators
rooting powders tissue culturing selective weed killers formation of seedless fruits ripening of fruit
explain rooting powders as a commercial use of plant regulators
horticulturists use NAA to promote rooting of stem cuttings
explain tissue culturing as a commercial use of plant regulators
small pieces of tissue cut off and grown in an artificial medium. form a callous, treated with a high concentration of auxin, it will form shoots and roots
explain selective weed killers as a commercial use of plant regulators
2,4-D a synthetic auxin is used as a selective weed killer. It disrupts normal growth of dicots and doesnt affect monocots
explain formation of seedless fruit as a commercial use of plant regulators
auxin is applied to flowers before fertilisation occurs so that the ovary enlarges and develops in a fruit without seeds eg. tomatoes
explain ripening of fruit as a commercial use of plant regulators
fruits such as bananas are picked when green. Before they are needed in a shop they are exposed to ethene so they all ripen at the same time
IAA
Indoleacetic acid
explain IAA
a naturally-occurring auxin often found in plants
3 places in the plant in which auxin is produced
apical meristems (shoot tip and root tip)
developing seed embryos and fruits
young developing leaves
5 functions of auxin
Controls:
- root and stem growth
- cell elongation and differentiation
- development of flowers and fruit
- apical dominance
- responses to external stimuli (tropisms)
explain cell elongation as an effect of auxins
weakens cell walls, links between cellulose fibres are broken, can take in H2O by osmosis and elongate
basis for tropisms
explain fruit developing as an effect of auxins
promotes setting and growth of fruit
produces seedless fruits when sprayed on artificially
explain apical dominance as an effect of auxins
auxin diffuses down the stem and inhibits growth of side branches
stem grows in length with very few side branches
abscisic acid
a plant growth regulator that inhibits growth
where is abscisic acid produced
stems leaves and green fruit
3 functions of abscisic acid
promotes bud and seed dormancy by slowing down growth
inhibits cell division
promotes leaf fall
tropism
growth response of a plant due to an external stimulus
positive tropism
growth towards a stimulus
negative tropism
growth away from a stimulus
importance of tropisms
to allow plants to have a favourable conditions for growth
5 types of tropisms
phototropism geotropism thigmotropism hydrotropism chemotropism
phototropism
growth response of a plant to light from a particular direction
stem grows towards light, positively phototrophic
geotropism
growth response of a plant to gravity
roots grow downwards, positively geotropic
thigmotropism
growth response of a plant to touch
hydrotropism
growth response of a plant to water
chemotropism
growth response of a plant to chemicals
role of auxin in phototropism 3
- auxin is produced in stem tip and diffuses down the stem
- if light comes from one direction, the auxin moves away from it
- unequal growth and bending towards the light
4 things that plants must protect themselves against
loss of water
overheating
being infected by microorganisms
being eaten
2 ways in which a plant can protect itself
structural or chemical adaptations
4 structural adaptations
thick cuticle
thorns
stinging cells
deep roots
thick cuticle
reduces water loss
thorns
to not be eaten
stinging cells
to not be eaten
deep roots
to absorb water from deep down in the ground
3 chemical adaptations
production of toxic chemicals
production of heat-shock proteins
production of antimicrobial chemicals
