lecture 8

Question 1

what is photomorphogenesis?

Answer 1

effects of light on plant morphology

Question 2

what are the 2 major classes of light receptors?

Answer 2

blue-light receptors and phytochromes

Question 3

what do blue-light photoreceptors control?

Answer 3

hypocotyl elongation, stomatal opening and phototropism

Question 4

what do phytochromes do?

Answer 4

regulate many of a plants responses to light throughout its life, including seed germination and shade avoidance

Question 5

what is photoperiod?

Answer 5

the relative lengths of night and day that plants use to detect the time of year. photoperiodism is a physiological response to photoperiod.

Question 6

what are short-day plants?

Answer 6

plants that flower when a light period is shorter than a critical length.

Question 7

what are long-day plants?

Answer 7

plants that flower when a light period is longer than a certain number of hours

Question 8

flowering in day-neutral plants is controlled by:

Answer 8

plant maturity

Question 9

where is photoperiod detected

Answer 9

leaves

Question 10

iclicker question: a short-day plant will flower only when:

Answer 10

NIGHTS are LONGER than a certain critical value

Question 11

how do sprouting plants know to grow toward the surface? (gravitropism)

Answer 11

it involves the sedimentation of starch-filled plastids (STATOLITHS) within the columella cells of the root cap (statocytes), which triggers a relocalization of plasma memb. associated auxin efflux facilitators to the lower side of the cell.

Question 12

what is the messenger in gravitropism?

Answer 12

auxin

Question 13

what is thigmotropism?

Answer 13

response to touch; it refers to changes in form that result from mechanical disturbance. also defined as the turning of all or part of an organism in a particular direction is response to external stimuli.

Question 14

what are the 3 tropisms?

Answer 14

1. phototropism
2. gravitropism
3. thigmotropism

Question 15

what are some abiotic stresses (environmental)?

Answer 15

drought, flooding, salt stress, heat stress, cold stress

Question 16

what are some biotic stresses (environmental)?

Answer 16

herbivores and pathogens

Question 17

what is a plants first line of defense against pathogens?

Answer 17

the barrier presented by epidermis and periderm

Question 18

what are effectors

Answer 18

pathogen-encoded proteins that cripple the hosts innate immune system

Question 19

what is the second level of plants immune defense? (against pathogens)

Answer 19

effector-triggered immunity

Question 20

what are R genes

Answer 20

disease resistant gene. R gene codes for an R protein.

Question 21

what are R proteins?

Answer 21

R proteins activate plant defenses by triggering signal transduction pathways. the defenses include the hypersensitive response and systemic acquired resistance.

Question 22

what does the hypersensitive response (pathogens) do?

Answer 22

causes cell and tissue death near the infection site.
induces production of enzymes that attack pathogens.
stimulates changes in the cell wall that confine the pathogen and then destroy themselves.
deprive the pathogen of nutrients

Question 23

what is the systemic acquired resistance? (pathogens)

Answer 23

causes systemic expression of defense genes and is a long-lasting response.

Question 24

how does the systemic acquired resistance work?

Answer 24

before infected cells die, they release signal molecules called methylsalicylic acid, it is synthesized around infection site and carried to phloem to other remote sites to be converted to salicylic acid, which triggers the defense system to respond rapidly to another infection.

Question 25

what are some physical defenses against herbivory?

Answer 25

thorns and trichomes

Question 26

what are some chemical defenses of herbivory?

Answer 26

distasteful or toxic compounds, such as an unusual amino acid called canavanine, that kills insects if they eat it.

Question 27

iclicker question: the transduction pathway that activates systemic acquired resistance in plants is initially signalled by____

Answer 27

salicylic acid