CHAPTER 31 PLANT RESPONSE TO INTERNAL AND EXTERNAL SIGNALS Flashcards
what are plant hormones?
chemical signals that modify or control one or more specific physiological process within a plant.
what is tropism?
any response resulting in curvature of organs toward or away from a stimulus
what is phototropism?
plant response to light observed that the grass seedling could bend toward light only if the tip of the shoot was present and exposed to light
what are the main plant hormones?
auxin, cytokinins, gibberellins, abscisic acids, ethylene
what is auxin?
produces in shoot tips and is transported down the stem, cell elongation, increasing the activity of proton pumps to loosen the cell walls including a lower ph activating expansions loosening the cell walls to grow longer
what is cytokinins
stimulate cytokinesis, working together with auxin to control cell division and differentiation
what is gibberellins?
many effects, seed germination and fruit growth
what is abscisic acid?
contributes to seed dormancy, drought tolerance
what is ethylene?
associated with apoptosis, triggers ripening fruit producers can control ripening by picking green fruit and controlling ethylene
what is photomorphogenesis?
light triggering many key events in plant growth and development
what is an example of a light receptor?
photochromes
what is photochrome receptors?
exist in two reversible states with the conversion of Pr (photo red light) to Pfr )photo triggering many development responses
red light
the conversation of Pr to Pfr sunlight increases the ratio of Pfr to Pr.
helps to flower, promote growth
what is far-red light?
triggers the conversion of Pfr to Pr, Pfr reverts Pr in the dark.
captures more sunlight increase growth
what is photoperiod?
the relative lengths of night and day, is the environmental stimulus plants use most often to detect the time of year
short-day plant
plants that flower when a light period is shorter than a critical length. are governed by whether the critical night light sets a minimum number of hours of darkness.
long-day plants
plants that flower when a light period is longer than a certain number of hours
day-neutral plants
is controlled by plant maturity, not photoperiod
critical night length
responses to photoperiod are actually controlled by the night length, not day length
what is gravitropism
environmental stress due to gravity, shoots show negative gravitropism by growing upward
- plants may detect gravity by settling of STATOLTHS dense cytoplasmic components
mechanism stimuli
gravity,light, movement, sun, touch
thigmotropism
is the growth in response to touch
environmental stress
stress can be abiotic (nonliving) flooding heat or biotic (living) pathogens
