Triggering of events

Question 1

Why do plants respond?

Answer 1

To increase evolutionary fitness as this maximises number of successful offspring

Question 2

Why are plant responses needed?

Answer 2

The environment is uneven and variable both biotically and abiotically

Question 3

How are plant responses coordinated?

Answer 3

By hormones which are released by cells

Question 4

How are plant hormones released?

Answer 4

By the whole organism so are decentralised

Question 5

How do plant hormones move?

Answer 5

By diffusion, active transport as mass flow so need to be small

Question 6

What are the types of triggering events?

Answer 6

Timed events through life and protecting against biotic and abiotic factors

Question 7

What are examples of time events through life?

Answer 7

Fruit ripening, seed germination, responding to abiotic stress and leaf loss

Question 8

What are examples of protecting against biotic and abiotic stress?

Answer 8

Responding to abiotic stress and producing defences against herbivory

Question 9

What controls fruit ripening?

Answer 9

Ethene

Question 10

What is a climacteric fruit?

Answer 10

It needs ethylene for ripening and continues to ripen after being picked

Question 11

What are examples of climacteric fruits?

Answer 11

Apples, bananas, mango, peach, pears, avocado and melon

Question 12

What is non-climacteric fruit?

Answer 12

Fruit that does not need ethylene to ripen

Question 13

What are examples of non-climacteric fruit?

Answer 13

Citrus, grapes, watermelon and strawberries

Question 14

How do supermarkets deal with ripening fruit?

Answer 14

They pick before ripe and keep cold so they can spend longe before becoming ripe and fruit is firm to reduce damage during transport

Question 15

What controls seed germination?

Answer 15

Gibberellins

Question 16

What inhibits germination?

Answer 16

Light, other than in certain plants such as poppies

Question 17

What is experimental evidence for the role of giberellins?

Answer 17

If mutant plants which lack to gene to produce gibberellins are produced, they will not germinate, but if gibberellins are applied, they will germinate.

Question 18

How do plants deal with abiotic stress when born into darkness?

Answer 18

Grow pale, as no chlorophyll and long and thin to maximise resources before reaching light

Question 19

How do plants cope with reeling?

Answer 19

Leaf loss, cytoplasm and vacuole contain solutes with lower freezing point and production of sugar, polysaccharides, amino acids or proteins to act as anti freeze

Question 20

Why do leaves fall off?

Answer 20

Reduce the chance of storm damage, nutrients can be re absorbed, little photosynthesis, minimise water loss and can use resources to prevent freezing

Question 21

What is senescence and abcission?

Answer 21

Growing brown and falling off

Question 22

What inhibits senescence?

Answer 22

Cytokines

Question 23

What inhibits abscission?

Answer 23

Auxins

Question 24

What happens when there is a drop in cytokines?

Answer 24

Senescence is initiated

Question 25

What is the result of senescence initiation?

Answer 25

A reduction in auxin production

Question 26

What is the result of a reduction of auxin?

Answer 26

Cells in the abscission zone become sensitive to ethene and this initiates cellulose production with digest cell walls, causing abscission

Question 27

What is synergism?

Answer 27

The interaction of 2 factors where the outcome is greater than the sum of the individual effects of either of them

Question 28

What is antagonism?

Answer 28

The interaction of 2 factors that are driving the outcome in opposite directions

Question 29

What are the environmental triggers for freezing response?

Answer 29

Sustained fall in temperature and reduction is day length

Question 30

What controls stomatal closure?

Answer 30

Absicic acid?

Question 31

When do stomata close?

Answer 31

When water is in short supply or in the dark

Question 32

When do leaf cells release ABA?

Answer 32

When under stress

Question 33

When do roots release ABA?

Answer 33

When soil water levels are low

Question 34

What happens when ABA is released?

Answer 34

Guard cells swell, stomata opens so ions move out of guard cells and water follows by osmosis, then guard cells become flaccid and stomata closes

Question 35

What are physical defences?

Answer 35

Hairs, thorns and spikes

Question 36

Wha is a movement defence?

Answer 36

Leaf folding of mimosa pudica

Question 37

What are volatile organic compounds?

Answer 37

Parasitoid attractants and inducers of defence

Question 38

What are examples of chemical defences?

Answer 38

Citronellal (an insect repellant), caffeine (toxic to fungi and insects) and tannin (bitter taste and toxic to insects)