chapter 39- plant response

plant response

ability of plants to detect envionmental signals and respond altering growth and development

example of plant reponse to environment

dodder plant bending toward a host due to chemical signals

3 stages of signal transduction

reception, transduction and response

A conformational change in a substance called phytochrome __________.

leads to de-etiolation

What happens immediately after a phytochrome is activated by light?

Ca²⁺ channels are opened, and guanylyl cyclase is activated.

reception

a signal binds to a receptor

transduction

signal is relayed through molecules like second messengers and proteins

response

activation of cellular responses (gene expression, growth changes)

etiolation

growth in darkness leads to pale stems, small leaves and weak roots

de-etiolation

normal growth in light (greening, leaf expansion, stronger roots)

what pigment is involved in light detection

phytochrome

plant hormones

chemical signlas that regulate growth and development

auxin

promotes cell eleongation and phototropism (growth towards light)

how does auxin move

polar (from tip downward)

function of cytokins

stimulate cell division and delay aging

apical dominance

main shoot suppresses side shoots (controlled by hormones)

function of gibberellins

stem elongation, fruit growth and seed germination

bolting

rapid stem growth before flowering

ABA

inhibits growth, and promotes seed dormancy

how does ABA help in drought

closes stomata to reduce water loss

function of ethylene

fruit ripening, leaf drop and stress responses

triple responses

slowed stem elongation, thickened stem and horizontal growth

photomorphogeneisis

growth and development in response to light

what can plants detect about light

direction, intensity and color (wavelength)

2 forms of phytochrome

Pr and Pfr

which form of phytochrome is active

Pfr which is triggered by light

what does Pfr control

germination, flowering, branching and biological clocks

circadian rhythyms

interal 24 hour cycles independent of environment

phototoperiodism

repsonse to length of day and night

what controls flowering

night length (critical night length)

short day plants

flower when days are shorter and nights are longer

long day plants

flower when days are long and nights are short

day neutral plants

flower regardless of light cycle

gravitropism

growth in response to gravity

root vs shoot response to gravitropism

root is positive and shoot is negative

what detects gravity

statoliths

thigmotropism

growth in response to touch (vines wrapping around objects)

thigmomorphogenesis

changes shape due to mechanical disturbance (rubbing of stems of younger plants result in them being shorter)

first line of defense againsr pathogens

epidermis and periderm

hypersensitive response

local cell death to stop infection

systemic acquired resistance

whole plant immunity after injection

molecular defense

chemical toxinsstrucu

structural defense

thorns, spines, and thick leaves

community level defenses

releasin chemicals to warn near by plants

cellulr defense

cells form trichomes, or irritants

tissue level defense

leaves thicken

organ level defense

leaves modifed to spines and stems to stems