9.1 5 Phytochrome and flowering

Question 1

Why is light vital for plants

Answer 1

no chlorophyll is formed
no photosynthesis
the plant will die

Question 2

Day length

Answer 2

determines bud development,flowering ,fruit ripening and leaf fall

Question 3

Photomorphogenesis

Answer 3

the process by which the form and development of a plant is controlled by the levels and type of light

Question 4

red light

Answer 4

stimulates germination - produces biologically active Pfr

Question 5

far red light

Answer 5

inhibits germination (has a larger wave length than red light)

Question 6

if seeds exposed to a flash of red light

Answer 6

will germinate

Question 7

flash of red light then far red

Answer 7

will not germinate

Question 8

what determine if a seed will germinate or not

Answer 8

the final flash

Question 9

Phytochrome

Answer 9

a plant pigment that reacts with different types of light and in turn affects the responses of the plant

Question 10

different types of phytochrome

Answer 10

Pfr absorbs far red light

Pr absorbs red light

Question 11

when one form of the pigment absorbs light

Answer 11

it is reversibly converted into the other form

Question 12

as seedling breaks through soil

Answer 12

when germinating produces Pr

when exposed begins to convert

Question 13

in dark

Answer 13

Pfr converted to Pr very slowly but no Pr converted back.–Pr more stable but Pfr more biologoically active

Question 14

Balance between the two pigments

Answer 14

affected by varying periods of light and dark affects plant metabolism

Question 15

in daylight hours

Answer 15

sunlight contains more red light than far red light so most is a Pfr

Question 16

24 hour period

Answer 16

photoperiod

Question 17

short-day plants

Answer 17

plants that flower when the day is short and the night is long e.g. strawberries and tobacco plant
temperate regions flower in spring and autumn when canopy that blocks light has not developed or has fallen off

Question 18

long-day plants

Answer 18

plants that flower in relatively long days and short nights
e.g.cabbages
in temperate regions in summer or futher from equator where there may be very long days

Question 19

day-neutral plants

Answer 19

flowering unaffected by length of day e.g.cucumbers -evolved in tropical regions where day length the same all year round -will have different cues such as available water

Question 20

environmental cue

Answer 20

is length of darkness -if night interrupted by flashes of light will not flower

Question 21

in short day plants

Answer 21

Pfr inhibits flowering and lack of Pfr allows to occur -in darkness converted to Pr so flowering occurs

Question 22

in long day plants

Answer 22

high levels of Pfr stimulate flowering

Question 23

in day neutral plants

Answer 23

levels of Pr and Pfr are similar so flowering not triggered by this factor

Question 24

Florigen

Answer 24

hypothetical plant horomone which is involved in the photoperiodic response

• thought to produced due to changing levels of phytochromes and transported to flowering buds
• look at experiment
• thought to be a form of mRNA called FTmRNA shown to be able to travel through the plasmodesmata
• goes to leaves then apex of shoot where other genes associated with flowering are activated