lecture 8 Flashcards
(27 cards)
what is photomorphogenesis?
effects of light on plant morphology
what are the 2 major classes of light receptors?
blue-light receptors and phytochromes
what do blue-light photoreceptors control?
hypocotyl elongation, stomatal opening and phototropism
what do phytochromes do?
regulate many of a plants responses to light throughout its life, including seed germination and shade avoidance
what is photoperiod?
the relative lengths of night and day that plants use to detect the time of year. photoperiodism is a physiological response to photoperiod.
what are short-day plants?
plants that flower when a light period is shorter than a critical length.
what are long-day plants?
plants that flower when a light period is longer than a certain number of hours
flowering in day-neutral plants is controlled by:
plant maturity
where is photoperiod detected
leaves
iclicker question: a short-day plant will flower only when:
NIGHTS are LONGER than a certain critical value
how do sprouting plants know to grow toward the surface? (gravitropism)
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.
what is the messenger in gravitropism?
auxin
what is thigmotropism?
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.
what are the 3 tropisms?
- phototropism
- gravitropism
- thigmotropism
what are some abiotic stresses (environmental)?
drought, flooding, salt stress, heat stress, cold stress
what are some biotic stresses (environmental)?
herbivores and pathogens
what is a plants first line of defense against pathogens?
the barrier presented by epidermis and periderm
what are effectors
pathogen-encoded proteins that cripple the hosts innate immune system
what is the second level of plants immune defense? (against pathogens)
effector-triggered immunity
what are R genes
disease resistant gene. R gene codes for an R protein.
what are R proteins?
R proteins activate plant defenses by triggering signal transduction pathways. the defenses include the hypersensitive response and systemic acquired resistance.
what does the hypersensitive response (pathogens) do?
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
what is the systemic acquired resistance? (pathogens)
causes systemic expression of defense genes and is a long-lasting response.
how does the systemic acquired resistance work?
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.
