Chapter 5: Response in plnats

Question 1

5 types of nastic responses

Answer 1

1. Photonasty
   - reponse to light
   - Japanese roses open in the early morning
2. Thermonasty
   - response to changes in the surrounding temperature
   - tulips open when temperature increase while close when temperature drop
3. Thigmonasty
   - response to vibration
   - Venus flytrap clamp its leaves shut to trap the insect
4. Seismonasty
   - response to mechanical stimulus
   - mimosa plant
5. Nyctinasty
   - circadian rhythm that response to darkness
   - river tamarind closes its leave at night and unfurl during daytime

Question 2

3 characteristics of nastic responses

Answer 2

• not all are growth response
• quicker and more apparent
• intended for survival

Question 3

4 characteristics of tropism

Answer 3

• permanent and influenced by hormone
• slow and not apparent
• response direction depend on the stimulus direction
• negative and positive

Question 4

5 types of tropism

Answer 4

1. Phototropism
   - shoot grow toward light
2. Hydrotropism
   - root grow towards water
3. Geotropism
   - shoot grow against gravity
   - root grow towards gravity
4. Chemotropism
   - root grow towards mineral salts
   - root grow away from toxic substances
5. Thigmotropism
   - response to touch
   - tendrils coil and wrap around object for support

Question 5

Parthenocarpy

Answer 5

• auxin is used to produce seedless fruits
• fruits is produced without fertilisation of ovule
• auxin is sprayed on the flower to promote cell division in ovary wall
• ovary mature without fertilisation
• seedless fruits is produced

Question 6

application of auxin in agriculture

Answer 6

• parthenocarpy
• encourage growth in crops
• induce dormancy in potatoes during storage

Question 7

application of gibberellin

Answer 7

• treat mutated dwarf plants
• promote reapid elongation of flower stem
• produce larger grapes
• promote germination of seeds during low temperature and light density

Question 8

application of cytokinin

Answer 8

• used in tissue culture technique
• promote division and differentiation of cells
• used together with auxin to form plant organs
• delay leaf senescence

Question 9

application of abscisic acid

Answer 9

• stimulate abscission of mature fruits, leaves and flower
• inhibit germination and growth
• induce seed dormancy

Question 10

application of ethylene

Answer 10

• promote faster and more uniform maturation
• promote simultaneous flowering in plants
• stimulate abscission and senescence

Question 11

definition of phytohormones

Answer 11

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

Question 12

role of auxin in phototropism

Answer 12

Positive phototropism

• auxin is produced in the shoot tips
• auxin accumulate in the shaded side
• auxin concentration is higher in the shaded side
• auxin stimulate cell elongation
• the cell in shaded site elongate
• plant grow faster in the shaded site
• thus stem of plant is bend towards the light

Question 13

function of agar and mica sheet in auxin experiment

Answer 13

Agar:

• permeable to plant hormones
• auxin diffuse through it

Mica sheet

• not permeable to plant hormones
• stop the diffusion of auxin to zone of elongation

Question 14

how to overcome seed dormancy

Answer 14

• break the external coat of seed by using knife or sandpaper
• microbial action and movement through digestion tract to break the external coat
• change the surrounding environment condition
• used gibberellin to stimulate the germination of seed