Coordination

Question 1

What is the control of flowering a result of?

Answer 1

The photoperiod - the relative length of days and nights

Question 2

What type of plants are short day plants (SDP)?

Answer 2

Plants that flower when day is short and night length is longer

Question 3

What type of plants are long day plants (LDP)?

Answer 3

Plants that flower when days are long and nights are short

Question 4

What is phytochrome?

Answer 4

A chemical in charge of the control of flowering

Question 5

What happens to P730 at night?

Answer 5

SLOWLY converts to P660

Question 6

What is the physiologically active form of phytochrome?

Answer 6

P730

Question 7

Is P730 inhibitory or stimulatory?

Answer 7

In LDPs P730 stimulates flowering, in SDPs it is inhibitory

Question 8

What does there need to be for a SDP to flower?

Answer 8

A long period of uninterrupted darkness, this allows enough time for the P730 to be converted back into P660 removing the inhibitory effect of P730

Question 9

What does there need to be for LDP to flower?

Answer 9

A short enough night length to prevent too much P730 being converted back into P660 - the concentration of P730 needs to be high enough to stimulate flowering

Question 10

What happens to LDP in a short day and long night?

Answer 10

P660 is converted to P730 during the day but the night is long enough for sufficient P730 to be slowly converted back to P660 to prevent the P730 reaching crucial level for flowering - NO FLOWERING

Question 11

What happens to LDP in long day and short night?

Answer 11

Long day length allows P660 to be converted to P730 in high concentration. The night is too short for enough P730 to be converted to P660. P730 builds up to critical length

Question 12

What happens to SDP in short day and long night

Answer 12

P660 is converted to P730 during day. Dark period is long enough for a sufficient level of P730 to be converted to P660 to remove inhibitory effect of P730.

Question 13

What happens to SDP in long day and short night?

Answer 13

P660 is converted to P730 during day but dark period is not long enough for sufficient level of P730 to be converted to P660 to remove inhibition of P730 - NO FLOWERING

Question 14

How do we match the supply and demand of flowers?

Answer 14

By manipulating their photoperiod.

Question 15

What is a hormone?

Answer 15

An organic compound produced in 1 part of an organism and transported to other parts to cause a response

Question 16

What plant hormones are there?

Answer 16

• Auxins
• Gibberellins
• Cytokinins

Question 17

What are auxins involved in?

Answer 17

Phototropism

Question 18

What direction does auxin travel in?

Answer 18

Away from the tip

Question 19

What do auxins do?

Answer 19

Cause cell elongation and are responsible for maintaining the structure of cell walls and if in high concentration can inhibit growth

Question 20

What do gibberellins do?

Answer 20

Elongate the internodal distance. This increases overall length of stem.

Question 21

What do cytokinins do?

Answer 21

Promote cell division in presence of auxin. They have also been shown to prevent the process of aging and breakdown of chlorophyll in older leaves

Question 22

What is a coleoptile

Answer 22

a baby plant <3

Question 23

How do auxins cause plants to grow towards light?

Answer 23

• Auxins produced in cells of apical meristems
• Diffuse down the shoot to zone of elongation
• Auxin binds to receptors in the cell membranes of newly formed cells in zone of elongation
• Cells pump H+ ions into the cellulose cell walls
• This acidification loosens the cross links in the cellulose microfibrils making the cell wall more flexible
• As the cells absorb water by osmosis the cell walls stretch more readily due to the hydrostatic pressure exerted
• The greater the concentration of auxin, the more flexible walls become