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Question 1

Some environmental signals? 6•

Answer 1

•Light intensity / spectral quality
•Water potential/ nutrients
•Temperature
•Day length/ photo period
•Herbivores / pathogens
•Gravity ( are u up or down)

Question 2

PAR (photosynthetic active radiation)?

Answer 2

Daily variability of sunlight availability.

Question 3

Plants can sense daily variability, but how about seasonal variability (PAR)?

Answer 3

Plants sense differences in the average PAR between seasons.

Question 4

Why do plants sense average PAR for season variability?

Answer 4

It is dangerous to have an unexpected different day within a season, and to induce morphological or chemical change based on that unexpected day.

Question 5

Do Sensing and responding systems in plants and animals similar?

Answer 5

Yes AT the cellular level.

Question 6

Receptors detect signals. How does this work and what happens next?

Answer 6

Phosphorylation cascades and second messengers (largely ions). This translate signals into a chemical language and relay the information to the target. This can lead to a regulation process that relates to DNA, such as activation/inactivation of certain proteins by being involved in transcription/translation alteration.

Question 7

phototrophism?

Answer 7

Response in plants that requires blue light. There is a specific receptor that recognizes the blue light.

Question 8

Phototropins? 4•

Answer 8

The •receptor that causes •phototropism, •stomata opening, and •shade avoidance.

Question 9

Phytochrome system?

Answer 9

The light switch of plants in which the chromophore switches between the Pr or Pfr conformation.

Question 10

Stomatal conductance?

Answer 10

How open the stomata are and how much water is lost through them.

Question 11

When increasing light intensity, what happens?

Answer 11

Stomata are open, and water is lost through them by transpiration.

Question 12

Are stomata opening (aperture) and chlorophyll absorption linked processes?

Answer 12

Yes

Question 13

Combination of dual blue/red light are most effect in?

Answer 13

Opening stomata.

Question 14

Out of blue/red right, which light is most important for stomatal opening, photosynthesis, and flowering?

Answer 14

Blue light since it initially opens the stomata, but only needs a little red light for the combination.

Question 15

How is blue light sensed?

Answer 15

By phototropins PHOT1 and PHOT2 receptors which are protein kinases. They are activated by interactions with Flavin mononucleotide (FMN) chromophore (a light absorbing molecule).

Question 16

In the absence of light, what does FMN bond to and with what bond?

Answer 16

Bonds to each LOV (oxygen voltage domain) via non-covalent bonds. No phosphorylation will occur, and no signal amplification. Stomata thus closes.

Question 17

In the presence of light, what does FMN bond to and what type of bond?

Answer 17

Each LOV domain binds covalently to the FMN chromophore, and allows auto phosphorylation to occur, which results in signal amplification. Stomata will thus be open.

Question 18

What allows auto phosphorlylation to occur after the receptor accepts a signal?

Answer 18

The receptor changes shape and reveals an area for ATP to stick to phosphorylate the phosphate group.

Question 19

Phosphorylated PHOT1/PHOT2 does what to the stomata to ensure opening?

Answer 19

Activates H+ -ATPases. Protons leave guard cells, and a concentration gradient occurs. Potassium and chlorine will enter the guard cells using K+ channels and H+/Cl- cotransporters, decrease solute potential, and attract water into the guard cells.

Question 20

Chloroplast distribution?

Answer 20

The movement of chloroplasts depending on the direction and intensity of light. If weak light, chloroplasts will move into the top, but if strong light, chloroplasts will move into the sides.

Question 21

Far Red light is poorly/largely and red light is poorly/largely absorbed by chlorophyll a?

Answer 21

Poorly, largely.

Question 22

Does red light or far red light go through leaves?

Answer 22

Far red light.

Question 23

Why is the FR:R ratio important?

Answer 23

Determines germination since it signals sunlight availability.

Question 24

Dormancy?

Answer 24

Ow metabolic activity.

Question 25

The FR:R ratio is sensed by?

Answer 25

A SINGLE photochrome receptor that moves between two conformations.

Question 26

P_r?

Answer 26

A receptor that absorbs red light and changes to Pfr, and the other way around for Pfr. The helix in one of the alpha complexes changes shape.

Question 27

Is Pfr activated or inactivated?

Answer 27

Activated.

Question 28

Is Pr activated or inactivated?

Answer 28

Inactivated.

Question 29

If there are a lot of red light, Pr becomes?

Answer 29

Pfr. Thus, there is a high Pfr:Pr ratio so more will be in its activated conformation to accept more far red light.

Question 30

If there is a high Pfr:Pr conformation, then?

Answer 30

Germination occurs.

Question 31

In shade, ratios?

Answer 31

•High Fr:R light ratio
•Low Pfr:Pr phytochrome ratio.

Low seed germination.

Question 32

In sun, ratios?

Answer 32

•Low FR:R light ratio
•High Pfr:Pr phytochrome ratio.

High seed germination

Question 33

Germination depends ONLY on the ______ intensity of R:FR ratio?

Answer 33

Last one ONLY!!

Question 34

What environmental condition can be used as a calendar for plants?

Answer 34

Plants use the phytochrome system to measure the night length.

Question 35

Sensing between presence to absence of light is fast/slow process?

Answer 35

Slow! During the night, Pfr reverts SLOWLY into Pr.

Question 36

In the absence of light, the ratio between Pfr:Pr?

Answer 36

Pfr:Pr ratio decreases in the absence of light.

Question 37

The lower the Pfr:Pr ratio detected at sunrise?

Answer 37

The longer the night length.

Question 38

What is primarily controlled by night length?

Answer 38

Flowering.

Question 39

Short night plants?

Answer 39

Plants that flower if there are short nights.

Question 40

What does short night plants require at sunrise to flower?

Answer 40

High Pfr:Pr ratio.