Plants and Environment

Question 1

What do plants sophisticated mechanisms do?

Answer 1

collect information about their environment and respond in ways that maximize fitness

Question 2

what happens when a sensory cell receives a stimulus?

Answer 2

it transduces the signal via receptors and produces hormones that carry information to target cells elsewhere in the body

Question 3

how do target cells respond to hormones?

Answer 3

via other receptors with changes in cell function

Question 4

how does a single plant hormone affect the plant

Answer 4

affect many different target tissues or processes

Question 5

how do several plant hormones affect the plant

Answer 5

can affect the same response: hormones don’t work independently

Question 6

how and where are plant hormones transported

Answer 6

transported in xylem, phloem, by diffusion or cytoplasmic streaming

Question 7

How do plants mainly respond to the environment

Answer 7

by changing growth and morphology

Question 8

what is positive phototropism

Answer 8

growth of plant tip towards light

Question 9

what is positive phototropism caused by

Answer 9

differential growth of cells on opposite sides of coleoptile

Question 10

if a shoot has a permeable barrier, what can it do?

Answer 10

it can still bend

Question 11

hypothesized hormone on agar block can be used to do what?

Answer 11

to bend the shoot either way depending on how the block is placed

Question 12

what way does the shoot bend?

Answer 12

it bends away from the side with more hormone

Question 13

what was the first plant hormone discovered

Answer 13

Auxin (the phototropic hormones)

Question 14

photoreceptors allow plants to do what?

Answer 14

detect the presence direction, intensity, and wavelength of light

Question 15

what colour light does a phototropic response occur with?

Answer 15

blue light (or full light)

Question 16

why do phototropic responses only occur with blue light?

Answer 16

because it is mediated by the light receptor phototropin that is specifically sensitive to the blue part of the light spectrum

Question 17

what lights are photosynthesis most effective with and why?

Answer 17

blue and red light because chlorophyll is most sensitive to these wavelengths

Question 18

what are phototropins?

Answer 18

blue light photoreceptors

Question 19

characteristics of phototropins

Answer 19

• proteins encoded by PHOT1/2 genes
• involved in phototropic response
• involved in light-dependent opening and closing of stomata

Question 20

what are cryptochromes involved in?

Answer 20

the timing of flowering

Question 20

phytochrome photoreceptors characteristics

Answer 20

• absorbs mainly red/far red light
• switches between two different confirmations
• involved in seed germination and shade avoidance

Question 21

what does red light do?

Answer 21

drives photosynthesis

Question 22

what does far-red light do?

Answer 22

indicates shade

Question 23

first stage of signal transduction

Answer 23

increases number of proton pumps in plasma membrane

Question 24

second stage of signal transduction

Answer 24

lowers pH in cell wall activating expansin enzymes that unzip cell wall structure

Question 25

third stage of signal transduction

Answer 25

H+ -ATPases also establish electrochemical gradient
-> ion/solute uptake in to cell

Question 26

fourth stage of signal transduction

Answer 26

turgor pressure increases expanding the loosened cell wall; cell get longer

Question 27

Role of hormone gibberellin in seed germination

Answer 27

promote growth, and abscisic acid inhibits growth (on and off signals)

Question 28

decreased auxin leads to…

Answer 28

increased ethylene sensitivity

Question 29

increased ethylene sensitivity leads to…

Answer 29

weakness of the cell walls at the base of leaf

Question 30

what are leaves and flowers response to light

Answer 30

they track the sun - daily movements

Question 31

what is spring flowering response to light

Answer 31

a seasonal response to changing day length

Question 32

what does photoperiod mean?

Answer 32

the relative length of day and night

Question 33

what does the plants response to the length of day and night involve?

Answer 33

involves photo-reversible phytochrome pigment, time measurement and a flowering hormone