8.1.8 - Phytochrome

Question 1

How Do Plants Detect Light?

Answer 1

Using photoreceptors, called phytochromes.

Question 2

What Are Phytochromes?

Answer 2

Molecules, which absorb light.

Question 3

What 2 Pigments Do Phytochromes Posses?

Answer 3

~ Pr.

~ Pfr.

Question 4

Describe Pr
(3 Points)

Answer 4

~ Inactive form of phytochrome.

~ Absorbs red light.

~ At a wavelength of 660nm.

Question 5

Describe Pfr
(3 Points)

Answer 5

~ Active form of phytochrome.

~ Absorbs far-red light.

~ At a wavelength of 730nm.

Question 6

Describe The Process Of Phytochromes Changing State, When Exposed To Light
(3 Points)

Answer 6

~ Pr absorbs red light -> forms Pfr.

~ Pfr absorbs far-red light -> forms Pr.

~ Darkness, Pfr is gradually converted into Pr.

Question 7

What Happens During The Day, With Regards To The Phytochrome State?
(3 Points)

Answer 7

~ Daylight contains more red light, then far-red light.

~ Pr -> Pfr, happens at a quicker rate.

~ Levels of Pfr rise.

Question 8

What Happens At Night, With Regards To The Phytochrome State?
(3 Points)

Answer 8

~ At night there is no light.

~ Pfr -> Pr, happens gradually.

~ Levels of Pr rise.

Question 9

What Occurs, If There Are High Levels Of Pfr Present?
(3 Points)

Answer 9

~ Pfr activates expression of genes, which stimulate flowering.

~ Activated gene, is then transcribed and translated.

~ Producing a polypeptide, causing flowering.