Chapter 14: Development and Morphogenesis

Environmental Complexity

Light

Gravity

Touch

Temperature

Water

Pests and Damage

Responding to Environmental Stimuli

Tropic Responses

Nastic Responses

Morphogenic Responses

Taxis

Communication within the Plant

Perception and Transduction

Chemical Messengers

Signal Amplification Cascades

all plant by slow mechanism

Activation and Inhibition of Shoots by Auxin

Cell Elongation

Apical Dominance

Differentiation of Vascular Tissues

Interactions of Hormones in Shoots

Hormones as Signals of Environmental Factors

Leaf Abscission

Tropisms

Flowering

Ripeness to Flower

Photoperiodic Induction to Flower

Endogenous Rhythms and Flowering

ABC Model of Flower Organization

Concepts

morphogenesis

differentiation

polarity

generation of shape of the plant

various organs

increase some cell become different from each other

formation

root

shoot axis

pattern establishment mechanism

cell location relative to epidermis cell

provides two important type of info

direction or more precisely

duration of light

gradient of light

time of year

selectively advantageous for many cell

to orient themselves

respect direction

plants do not move around

frequently grow against bojects

respond contact

fluctuates in predictable pattern

daily

yearly axis

prerequisite for life

does not act like a signal in the way other factors

plant must detect when they being attacked by

pests such as

bacteria

fungi

insects

digestive enzymes

growth response oriented with regard to stimulus

plagiotropism

growth at angle

thigomotropism

touch is stimulus

chemotropism

pollen tubes for flowering plant suspect

growing a long

probably from synergids

differential growth

contact side slowing

opposite side accelerating

both

stereotyped nongrowth

not oriented with regard to stimulus

diurnal

active during daylight

nocturnal

active at night

photonastic

opening and closing in same manner

light given artificially from

west

northsouth

above

below

sleep movement

blade elevated in the day

lowered at night

morphogenetic response

change "quality" of plant

cell swim toward

away from stimulus

statocytes

root caps

have large starch granules

statoliths

sink in response to gravity

two important factors in preception&transduction

presentation time

threshold

length of time the stimulus present for perceptive cells

to react

complete transduction

level of stimulus must present during presentation time to cause

perception

transduction

all-or-none response

after the threshold

present time requirement are met

stimulus not long important

dosage-dependent responses

amount or duration of stimulus effect

transport of hormones through plant

hormones

organic chemicals produced in one part of plant

then transported to other

thousands of messenger molecules

not just original

chances are very high will enter nucleus

encounter proper genes quickly

in young cell internodes below apical meristem

auxin triggers cell elongation

result being each shoot tip has only one

apically produced auxin induces dormancy

in axillary buds

third site of response t auxin produced in shoot tip

response is cell division

and morphogenesis

apical dominance absence of auxin

normal growth of shoot

root result in

large flows of auxin

cytokinin

environmental factor influenece

blue-light responses

blue-light stimulates other aspects of plant development

coleoptile

shows strong positive phototropic

oat seed have outermost protective leaf

oat coleoptiles are organ studied

juvenile phase

plants are incapable induced to flower

adult phase

sensitive to floral stimuli

phage change

conversion from juvenile to adult

photoperiod

short-day plants

transition to flowering is triggered

day are short

spring or fall

long-day plants

days are long

summer

day-neutral plants

do not respond to day length

phytochrome

detects the presence

absence of light

critical night length

varies from species to species

endogenous rhythms

metabolism cycle repeatedly between two states

cycle controlled by internal factor

negative feedback loop

clock is poorly understood

entrain

reset the rhythm

circadian rhythm

period approximately 24 hrs long

exactly 24 hrs long

ABC model

most flowers can explain by hypothesis

homeotic mutation

organ develop in unexpected site

image

image

image

interplay of two or three hormones