f5 chap 5: response in plants Flashcards
whats the definition of tropism responses?
(i)responses of certain parts of a plants
(ii) such as roots and shoots
(iii) that respond towards or away from a stimulus
characteristics of tropism
(i) slow response, not apparent
(ii) positive tropism: growth towards direction of stimulus
(iii) negative tropism: growth away from stimulus
which plant response is permanent and influenced by plant hormones
tropism
what are the types of tropism?
thigmotropism, geotropism, chemotropism, hydrotropism, phototropism
explain chemotropism
chemotropism is the response of plants towards chemicals. for example, roots show positive chemotropism when they grow towards mineral salts and negqative chemotropism when the grow away from poison
what response is it when a plant grows towards light?
phototropism
what are the types of nastic responses?
photonasty, seismonasty, nyctinasty, thermonasty, thigmonasty
characteristics of nastic responses
(i) response is quicker, more apparent than tropism
(ii) not all nastic responses are growth responses
(iii) some nastic responses are intended for survival
whats hydrotropism
plant response to water
whats phototropism
plant response to light
whats thigmotropism
plant response to touch
whats geotropism
plant response to gravity
whats nyctinasty
circadian rhythm that responds to onset of darkness
whats thermonasty
plant response to change in temperature
whats thigmonasty
plant response towards vibration
whats seismonasty
plant response that occur due to mechanical stimulus like shock, wind, touch and raindrops
in which plant can photonasty be observed?
japanese roses. it opens when it receives maximum sunlight and closes at night
whats photonasty
plant response to light
in which plant can seismonasty be observed?
mimosa plant
which part of the plant can seismonasty response be seen?
leaves, stigma and stamens
in which plant can nyctinasty be observed? explain.
river tamarind. it closes its leaves at night and unfurls them during daytime
in which plant can thermonasty be observed?. explain
tulips. it opens when theres an increase in temperature, closes when temperature drops
what response can be seen in venus flytrap?
thigmonasty
what response can be seen in tulip?
thermonasty
what response can be seen in river tamarind?
nyctinasty
what are phytohormones?
chemical substances that stimulate and coordinate responses in plants, at low concentration
state 5 types of phytohormones
auxin, ethylene, abscisic acid, gibberellin and cytokinin
state 2 functions of auxin
(i)stimulates growth and elongation in root and shoot cells
(ii) inhibits growth of lateral buds
state 2 functions of gibberellin
(i) stimulates growth of flowers in dwarf plants
(ii) inhibits development of roots
state 2 functions of cytokinin
(i) stimulates seed germination
(ii) delays leaf senescence
state 2 functions of abscisic acid
(i) induces seed dormancy
(ii) inhibits growth of plants
state 2 functions of ethylene
(i) stimulates ripening in fruits
(ii) stimulates abscission of leaves and fruits
which phytohormone inhibits abscission of fruits and young leaves?
auxin
which phytohormone stimulates cell division in cambium during secondary growth?
auxin
in which tropisms is auxin functional in?
phototropism and geotropism
which phytohormone stimulates development of apical dominance in shoots and roots?
auxin
which phytohormone stimulates development of adventitious roots at the end of stem cuttings?
auxin
which phytohormone stimulates growth and elongation in the stem cell?
gibberellin
which phytohormone stimulates development of leaves, flowers and fruits?
gibberellin
which phytohormone stimulates development and germination of seeds?
gibberellin
which phytohormone stimulates division and elongation of root and stem cells when auxin is present?
cytokinin
which phytohormone stimulates seed germination?
cytokinin
which phytohormone inhibits development of apical dominance?
cytokinin
which phytohormone delays leaf senescence?
cytokinin
which phytohormone stimulates growth of lateral buds?
cytokinin
which phytohormone inhibits growth of plant?
abscisic acid
which phytohormone induces seed dormancy?
abscisic acid
which phytohormone stimulates abscission of mature fruits, leaves and flowers?
abscisic acid
which phytohormone induces stomatal closing during drought season?
abscisic acid
which phytohormone inhibits growth of buds and seed germination?
abscisic acid
which phytohormone stimulates ripening in fruits?
ethylene
which phytohormone stimulates senescence process in plants?
ethylene
which phytohormone stimulates abscission of leaves and fruits?
ethylene
what phytohormone controls growth response in plants?
auxin
explain the effect of auxin on growth response
- auxin synthesised at coleptile tips stimulate ** cell elongation**
- auxin distribution influences direction of shoot growth
3.uniform distribution auxin cause coleptile to grow upwards - area which receives more auxin will grow faster and cause coleptile to curve to side that receives less or none auxin
explain the role of auxin in phototropism
- distribution of auxin in shoots is uniform if shoots are exposed to light from all direction
- causes shoots to grow up
- shoots are exposed to light from one direction, auxin will move away from light
- auxin concentration is higher on shaded side 5. cells in shaded side elongate more than cells in bright side
6 so, shoot bends towards light
role of auxin in geotropism
- seeds germinate horizontally, gravity cause auxin pool at bottom side of tip and roots
- high auxin concentration cause cells at bottom to grow faster and also allow shoot to bend up)
- high auxin concentration at bottom of roots prevent root elongation and cause root to go down