Transcript Ch 38 and 39 Plant Hormones

Fragmentation: Pieces develop into a whole
offspring
Vegetative Reproduction: New plants come
from mature fragments, tough
Apomixis: (Dandelions) Produce seeds w/o
fertilization or pollination – makes mature
seeds
Benefits
-
No need for a pollinator
(sparsely distributed)
-
Identical offspring
-
Typically stronger
offspring (come from
mature fragments)
Disadvantages
- Identical offspring
Benefits
-
Large number of
offspring to overcome
odds of fragile seeds
-
Varied offspring to
withstand env. Changes
-
Further seed dispersal
-
Dormant seeds until
favorable conditions
avail.
Disadvantages
- Fragile seeds (disease,
predators)
 You

can be anything you want to be!
Especially in meristems
 House

Creates a mass of dividing, undifferentiated,
totipotent cells at the cut end
 Can

plants, shoot cuttings
also be grafted onto a new plant!
Might both have their own beneficial features

Resist pathogens, quality of fruit
Asexual
propagation
 Transgenic:
Engineered to express a gene
from another species
BT Corn?!?
Figure 38.14
 Increasing
quality of the rice, malnutrition
Genetically modified rice
Has helped children
with Vitamin A
deficiency
(blindness) –
Increased beta
carotene
Ordinary rice
Figure 38.15
Figure 38.16

May transfer allergens from a gene source to a
plant used for food

Effect nontarget organisms – Monarch
Butterflies

Transgene Escape – Crop/Weed hybridization,
creating superweeds
A look at hormones and
plant response



Vampire Plant: Parasitic,
non-flowering
Attaches to and feeds off
of host (Tomato)
Attracted by the scent of
the host (chemical signals)
 Etiolation:
Growth in complete/partial
darkness



Weak stems
Pale Leaves
Yellow Color
 Benefit
for underground plants that don’t
need expanded leaves or extensive root
system to combat transpiration
 De-etiolation
 The
plant undergoes profound
change
 Stem
elongation
 Leaves and roots expand
 Producing chlorophyll
1) Reception- signals are detected by receptors

Proteins that change in response to specific stimuli



Phytochrome, Cytoplasm, Functions in light detection (deetiolation)
Other: Hormone Signals
Other: Environmental Triggers
2) Transduction- secondary messengers

Transfer and amplify signals that cause specific
responses

Ca2+ and cGMP
 Leads
to a regulation of one or more
cellular or enzymatic activities
Post-Translational modification
 Transcriptional regulation

Ultimately
switch genes
on and off to
regulate
proteins
 Phototropism:
Directs shoot growth towards
sunlight

Dark side elongates faster than the light side to
allow the plant to bend
Location:
Accumulates in
meristem region
(shoot tips),
Developing seeds
and fruits
 Carries
information
about development,
size and environment

How does my branch
look?
 Dormant
plant
reduces auxin
transport capacity and
the expression of
genes
 Location:
Meristems and Seeds
 Stimulate stem elongation and leaf growth
 Fruit growth

Work with Auxin
Spray used
commercially,
seedless grapes
Larger
More spacing at
notes
 Signals
seed to break dormancy
 Stimulates synthesis of amylase to
breakdown stored sugars
 SLOWS
GROWTH!!!!

High levels of ABA
during seed dormancy

Closes stomata during
drought
Affects calcium
messengers causing
Location: All
parts of the
plant
K channels of guard cells
to open…
Water is lost…. Turgor
pressure is lost…
Stomata close
Response to stress (drought, pressure, injury,
infection)
 A change in the balance of auxin and ethylene
controls leaf abscission


The process that occurs in autumn when a leaf falls
 Attract
animals, Seed dispersal
 Done commercially, transporting produce
Many legumes

Lower their leaves in the evening and raise them in the
morning
Noon
Figure 39.21
Midnight
 Roots
Down
 Shoots Up
See Growth in response to
touch, Vines
 Result
from mechanical perturbation
 Ex: Rubbing the stems of young plants a couple of
times daily, Results in plants that are shorter than
controls
(a) Unstimulated
(b) Stimulated
Side of pulvinus with
flaccid cells
Leaflets
after
stimulation
Side of pulvinus with
turgid cells
Pulvinus
(motor
organ)
(c) Motor organs
Vein
0.5 m
 Environmental
stresses adversely effect plant’s
survival, growth, and reproduction

Crop yields in agriculture
 Luckily




equipped with many natural defenses
Toxins
Needle shaped cells crystals in cells, irritant
Hard to chew
Recruit predatory animals defend against herbivores