f5 chap 5: response in plants

Question 1

whats the definition of tropism responses?

Answer 1

(i)responses of certain parts of a plants
(ii) such as roots and shoots
(iii) that respond towards or away from a stimulus

Question 2

characteristics of tropism

Answer 2

(i) slow response, not apparent
(ii) positive tropism: growth towards direction of stimulus
(iii) negative tropism: growth away from stimulus

Question 3

which plant response is permanent and influenced by plant hormones

Answer 3

tropism

Question 4

what are the types of tropism?

Answer 4

thigmotropism, geotropism, chemotropism, hydrotropism, phototropism

Question 5

explain chemotropism

Answer 5

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

Question 6

what response is it when a plant grows towards light?

Answer 6

phototropism

Question 7

what are the types of nastic responses?

Answer 7

photonasty, seismonasty, nyctinasty, thermonasty, thigmonasty

Question 8

characteristics of nastic responses

Answer 8

(i) response is quicker, more apparent than tropism
(ii) not all nastic responses are growth responses
(iii) some nastic responses are intended for survival

Question 9

whats hydrotropism

Answer 9

plant response to water

Question 10

whats phototropism

Answer 10

plant response to light

Question 11

whats thigmotropism

Answer 11

plant response to touch

Question 12

whats geotropism

Answer 12

plant response to gravity

Question 13

whats nyctinasty

Answer 13

circadian rhythm that responds to onset of darkness

Question 14

whats thermonasty

Answer 14

plant response to change in temperature

Question 15

whats thigmonasty

Answer 15

plant response towards vibration

Question 16

whats seismonasty

Answer 16

plant response that occur due to mechanical stimulus like shock, wind, touch and raindrops

Question 17

in which plant can photonasty be observed?

Answer 17

japanese roses. it opens when it receives maximum sunlight and closes at night

Question 17

whats photonasty

Answer 17

plant response to light

Question 18

in which plant can seismonasty be observed?

Answer 18

mimosa plant

Question 19

which part of the plant can seismonasty response be seen?

Answer 19

leaves, stigma and stamens

Question 20

in which plant can nyctinasty be observed? explain.

Answer 20

river tamarind. it closes its leaves at night and unfurls them during daytime

Question 21

in which plant can thermonasty be observed?. explain

Answer 21

tulips. it opens when theres an increase in temperature, closes when temperature drops

Question 22

what response can be seen in venus flytrap?

Answer 22

thigmonasty

Question 23

what response can be seen in tulip?

Answer 23

thermonasty

Question 24

what response can be seen in river tamarind?

Answer 24

nyctinasty

Question 25

what are phytohormones?

Answer 25

chemical substances that stimulate and coordinate responses in plants, at low concentration

Question 26

state 5 types of phytohormones

Answer 26

auxin, ethylene, abscisic acid, gibberellin and cytokinin

Question 27

state 2 functions of auxin

Answer 27

(i)stimulates **growth and elongation** in root and shoot cells (ii) inhibits growth of **lateral buds**

Question 28

state 2 functions of gibberellin

Answer 28

(i) stimulates growth of flowers in dwarf plants (ii) inhibits development of roots

Question 29

state 2 functions of cytokinin

Answer 29

(i) stimulates **seed germination** (ii) delays leaf senescence

Question 30

state 2 functions of abscisic acid

Answer 30

(i) induces seed dormancy (ii) inhibits growth of plants

Question 31

state 2 functions of ethylene

Answer 31

(i) stimulates ripening in fruits (ii) stimulates abscission of leaves and fruits

Question 32

which phytohormone inhibits abscission of fruits and young leaves?

Answer 32

auxin

Question 33

which phytohormone stimulates cell division in cambium during secondary growth?

Answer 33

auxin

Question 34

in which tropisms is auxin functional in?

Answer 34

phototropism and geotropism

Question 35

which phytohormone stimulates development of apical dominance in shoots and roots?

Answer 35

auxin

Question 36

which phytohormone stimulates development of adventitious roots at the end of stem cuttings?

Answer 36

auxin

Question 37

which phytohormone stimulates growth and elongation in the stem cell?

Answer 37

gibberellin

Question 38

which phytohormone stimulates development of leaves, flowers and fruits?

Answer 38

gibberellin

Question 39

which phytohormone stimulates development and germination of seeds?

Answer 39

gibberellin

Question 40

which phytohormone stimulates division and elongation of root and stem cells when auxin is present?

Answer 40

cytokinin

Question 41

which phytohormone stimulates seed germination?

Answer 41

cytokinin

Question 42

which phytohormone inhibits development of apical dominance?

Answer 42

cytokinin

Question 43

which phytohormone delays leaf senescence?

Answer 43

cytokinin

Question 44

which phytohormone stimulates growth of lateral buds?

Answer 44

cytokinin

Question 45

which phytohormone inhibits growth of plant?

Answer 45

abscisic acid

Question 46

which phytohormone induces seed dormancy?

Answer 46

abscisic acid

Question 47

which phytohormone stimulates abscission of mature fruits, leaves and flowers?

Answer 47

abscisic acid

Question 48

which phytohormone induces stomatal closing during drought season?

Answer 48

abscisic acid

Question 49

which phytohormone inhibits growth of buds and seed germination?

Answer 49

abscisic acid

Question 50

which phytohormone stimulates ripening in fruits?

Answer 50

ethylene

Question 51

which phytohormone stimulates senescence process in plants?

Answer 51

ethylene

Question 52

which phytohormone stimulates abscission of leaves and fruits?

Answer 52

ethylene

Question 53

what phytohormone controls growth response in plants?

Answer 53

auxin

Question 54

explain the effect of auxin on growth response

Answer 54

1. **auxin synthesised** at coleptile tips stimulate ** cell elongation** 2. auxin distribution influences direction of shoot growth 3.**uniform distribution** auxin cause coleptile to **grow upwards** 4. area which receives **more auxin** will **grow faster** and cause coleptile to curve to side that receives less or none auxin

Question 54

explain the role of auxin in phototropism

Answer 54

1. distribution of auxin in shoots is uniform if shoots are exposed to light from all direction 2. causes shoots to grow up 3. shoots are exposed to light from one direction, auxin will move away from light 4. 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

Question 54

role of auxin in geotropism

Answer 54

1. seeds germinate horizontally, gravity cause auxin pool at bottom side of tip and roots 2. high auxin concentration cause cells at bottom to grow faster and also allow shoot to bend up) 3. high auxin concentration at bottom of roots prevent root elongation and cause root to go down