plant responses 2

Question 1

what are the three types of plant responses

Answer 1

1. chemical responses
2. tropisms vs nastic responses
   3.positive and negative tropisms

Question 2

what are the chemical defences of plants under stress

Answer 2

• tannins make leaves taste bad
• alkaloids make leaves tastes better
• Pheromones released by one organism that can affect the behaviour of other plants

Question 3

what are tropisms and nastic responses

Answer 3

• tropisms are directional (eg plant growing towards the light)

• nastic responses are non directional (eg closing of a venus fly trap due to touch)

Question 4

what is phototropism

Answer 4

1. shoots grow towards light
2. flowers turn towards light source
3. enables them to photosynthesise more

Question 5

what is geotropism

Answer 5

•roots grow towards the pull of gravity

• anchors them into soils

•helps to take up water

Question 6

what is chemotropism

Answer 6

1.occurs on flowers
2. pollen tubes grow down the style towards ovaries
3.they are attracted by chemicals.

Question 7

what is thigmotropism

Answer 7

shoots out of climbing plants wind around other plants for support

Question 8

How to plant responses come about?

Answer 8

•hormones (produced in a variety of cells) co ordinate plant response.
(knows as plant growth regulators)
• move around the plant by:
1. diffusion
2. Active transport
3. mass flow

Question 9

what is meant by synergic and antagonistic

Answer 9

synergic - hormones amplify each others effects.

antagonistic - oppose each others effects

Question 10

what is the role of auxin (as a plant hormone)

Answer 10

• regulating plant growth
• inhibits growth of side shoots
• inhibits leaf abscission

ACTION :
•causes cell elongation
•increases stretchiness of cell wall (increasing the AT of hydrogen ions)
• ATPase enzyme moves more ions through the plasma membrane, into the cell wall
• Low pH allows wall loosening enzymes to work
• These break bonds in the cellulose, allowing the cells to expand

Question 11

What is the role of Cytokinins

Answer 11

• Promotes cell division
• Delay leaf senescence (aging)
• Overcome apical dominance
• Promote cell expansion

Question 12

role of giberellinns

Answer 12

• Promote seed germination and growth of stems

Question 13

role of ethene

Answer 13

• Promotes fruit ripening

Question 14

role of abscisic acid

Answer 14

• Inhibits seed germination and growth
• Causes stomatal closure when plant stress by low water availability.

Question 15

where is auxin produced

Answer 15

at the apex of meristematic tissue

Question 16

what is apical dominance

Answer 16

the inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of the plant shoot

Question 17

what is IAA

Answer 17

indol-3-acetic acid (IAA) is the first auxin to be identified.