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Ch 14 Development and Morphogenesis (Environmental Complexity (Gravity…
Ch 14 Development and Morphogenesis
Environmental Complexity
Light
provides 2 important types of info about environment
direction
gradient of light
duration of light
length of day
Gravity
weight of stem
roots grow downward more likely to encounter water and minerals
shoots grow upward grow above other plants and encounter better conditions
Touch
venus fly trap
roots cannot grow against stone
some touch is good, some is bad
Temperature
metabolism does not occur above 1oC to 7oC
vernalization
cold treatment necessary for biennials to initiate flowering
low temps are required for trees and shrubs to induce deep dormancy
Water
without water plants wilt
roots that grow away from water grow slowly
they grow towards gravity
Pests and Damage
have two ways to detect damage
physical damage
digestive enzymes
Responding to Environmental Stimuli
Tropic Responses
a growth response oriented with regard to stimulus
plagiotropism
growth at an angle
thigmotropism
when touch is the stimulus
chemotropism
growing along the style to the ovary
differential growth
changing directions
growth on the contact side slowing
growth on opposite side accelerating
both
Nastic Responses
stereotyped nongrowth response that is not oriented with regard to the stimulus
diurnal species
active during the day
nocturnal species
active at night
photonastic
opening and closing always happens in same manner
Morphogenic Responses
causes a change in the quality of the plant
occurs in the metabolism
Taxis
is a response in which a cell swims toward or away from the stimulus
Communication Within the Plant
Perception and Transduction
statocytes
do have large granules
statoliths
sink in response to gravity
Presentation Time
length of time the stimulus must be present for the perceptive cells to react and complete transduction
Threshold
level of stimulus that must be present during the presentation time to cause perception and transduction
all-or-none response
after the threshold and presentation time requirement are met the stimulus is no longer important
dosage-dependent responses
amount of stimulus affects the amount of the response
Chemical Messengers
Hormones
organic chemicals produced in one part of the plant and transported to another where a response is initiated
Auxin
first plant hormone
cytokinins
named for the fact their addition to tissue culture
gibberellins
numbered
defined by structure
complex
ethylene
only gaseous plant hormone
climacteric
sudden burst of ethylene and rapid completion of maturation of fruit
brassinosteroids
leaf morphogenesis
root and stem growth
vascular differentiation
Jasmonic acid
defense against animals and fungi
salicyclic acid
resistance to pathogens and viruses
Signal Amplification Cascades
Activation and Inhibition of Shoot by Auxin
Cell Elongation
auxin trigger elongation
cells grow
Apical Dominance
suppression of auxiliary buds by the growing active apical bud of a shoot
Differentiation of Vascular Tissues
cell division and morphogenesis
three separate target tissues give three separate responses
Hormones as Signals of Environmental Factors
Leaf Abscission
fruits cannot
abscission
shedding of an organism
Tropisms
blue light responses
plant developmental responses triggered by blue light
coleoptile
shows a strong positive phototropic response
Flowering
Ripeness to Flower
juvenile phase
plants are incapable of being induced to flower
adult phase
sensitive to floral stimuli
phase change
conversion of juvenile to adult
Photoperiodic Induction to Flower
photoperiod
day length
short day plants
fall/spring
long day plants
summer
day neutral
doesn't depend on day length
phytochrome
detects presence or absence of light
Endogenous Rhythms and Flowering
certain aspects of their metabolism cycle repeatedly between two states
ABC Model of Flower Organization
hypothesis that three genes A, B, & C, interact to control the basic aspect of flower organization
gene A
outer most, lowest region of shoot apical meristem
gene B
partially over laps A & C
gene C
upper most, central region
