Download Interactions of Vascular Plants with Their Environment Tropisms

Interactions of Vascular Plants with
Their Environment
By
Ashley Nunez
Tropisms
 Tropism: is an invariable
growth response to an
environmental stimulus
occurring in plants and
primitive invertebrates.
 Irritable Reaction: is the
capacity to respond in a
characteristic way to
changes in the
environment.
 “Positive”
 “Negative”
http://cccmkc.edu.hk/~sbjbiology/AL%20BIO/Continuity%20of%20life%20growth%
20and%20development/Tropism_hydrotropism%20and%
20geotropism%20competing.htm
Geotropism
 A.B. Franck, 1869
(introduced geotropism
as a term).
 Statolith Theory:
postulates that plant
organs perceive gravity
through the movement
of starch grains (not
universally accepted).
 Centrifugal force,
mutant plants, and
golgi bodies.
Environmental Changes
 Vascular Plants (tracheophytes): Have evolved
an apparatus of conducting tubules.
 The link between animals (heterotrophs) and
plants (autotrophs).
 Plants do detect changes in their environment
and react to these changes in a specific way.
 Types of Responses:
Movement (but not usually locomotion).
Alteration of growth patterns.
Developmental phenomena.

Change in the state of particular plant structures.
Hydrotropism
http://www.studentsguide.in/biology/growth-development-angiosperms/paratonicgrowth-movements.html
Phototropism
http://botit.botany.wisc.edu/images/130/Tropisms/Phototropism/P
hototropism_MC_.html
http://www.cartage.org.lb/en/themes/Sciences/BotanicalScienc
es/PlantHormones/Nutrition/Nutrition.htm
Thigmotropism
http://www.science-projects-resources.com/simple-science-fairprojects.html
Plant Hormones
 Tropisms, as well as other phenomena occurring
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in the plant, are probably mediated by plant
hormones.
One of the first hormones to be discovered in
plants was auxin, by Fritz Went in 1926.
Hormone: is a substance produced in one part of
a living organism that has profound metabolic
effects throughout the organism as it travels
through the vascular system.
Hormones are chemical mediators of function and
behavior.
Relatively slow responses compared to faster
neural responses (found only in animals).
Auxin
Auxin effects:
The suppression of the
lateral buds along the stem.
The development of the
root and shoot system.
The growth of the fruit.

Dropping off of the leaves
and fruit (abscission).

Division of cells in the
cambium.
Auxin Continued..
 Auxin-like
substances were
produced as
weed killers.
 Acted primarily
on broad-leaved
varieties of
weeds.
 Agent Orange
Cytotoxins
 First discovered in the
tissue cultures
laboratories of Folke
Skoog et al. at the
University of
Wisconsin.
 Isolated as breakdown
products from plant
nucleic acids.
 Dr. D.S. Letham of
New Zealand isolated
zeatin from corn seeds
(active cytotoxin).
 Work in conjunction
with auxins.
 Cytotoxins Effects:
Focused effects on
cell division.
http://www.mesoblast.com/images/imagesmesoblast_cell_division_still.jpg
Gibberellins
 Originally associated with a fungus named


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
Gibberella fujikuroi (caused rice plants to be
abnormally high) .
Various gibberellins have also been found in plant
tissues themselves.
Termed “Foolish-seeding disease” by the
Japanese.
Increase of stem length in various dwarf plants.
The green revolution and its effect on dwarf
strains of rice and other agricultural staples.
May also increase plant height and alter both
vigor and nutritional yield.
Gibberellins Continued….
 The effects of
gibberellins is not
confined to
increasing plant
height.
 Gibberellins also:
Influence the
formation of enzymes
(hydrolyze starch).
May break down the
dormancy of seeds.
Bring about flowering
under certain
conditions.

In their absence,
produce no flowers at
all.
http://belladia.typepad.com/photos/uncategorized
/2007/08/13/flowermosaic.jpg
Gibberellins Continued….
 Negative effect on plant
vigor because it limits
their application on
agriculture.
 Synthesized in a manner
similar to steroid
hormones in vertebrates.
 Resemble sex steroids in
structure.
 They transverse cell
membranes rapidly.
http://4e.plantphys.net/images/ch20/wt2002b_s.jpg
Ethylene
 A unique hormone,
because it exists as
a gas rather than a
liquid.
 Associated with
rapid ripening of
fruit.
 Produced by the
plant itself, usually
when the fruit has
reached its
maximum size.
 Also added
externally by
handlers to bring
about ripening.
http://www.iesnz.co.nz/webfiles/IES/webpages/im
ages/2185/ethylene.jpg
Ethylene Continued…
 Senescence (aging and
degradation): is the
change in the biology of
an organism as it ages
after its maturity
(http://en.wikipedia.org/
wiki/Senescence).
 Leaf abscission is
mediated by ethylene.
 Termed “chief
messenger of death” by
botanists.
 Marks the end of each
growing season
http://www.biologyreference.com/images/biol_04_img0409.jpg
http://botit.botany.wisc.edu/images/130/Leaf/Leaf_abscission_M
C.low.jpg
Inhibitors
 A variety of inhibitors, which are not primary
hormones, may also play a role in maintaining
dormancy and resisting growth.
 Inhibitor hormones complement the influence of
ethylene.
http://wwwmgs.bionet.nsc.ru/mgs/papers/goryachkovsky/plant-trrd/image6.gif
Abscisic Acid (ABA)
 Synthesized by chloroplasts, but small amounts

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

are also synthesized by apical meristems in the
root and shoot.
A single compound unlike auxins, gibberellins,
and cytotoxins.
Induces dormancy in seeds, buds, and cambial
layers.
Stress hormone.
Leaf abscission and adverse conditions.
High concentrations of ABA: protective scales,
watertight resins increase, and stomata closes.
Photoperiodism
 The ability to respond to
relative periods of light and
darkness (not confined to
plants).
 Flowering is a specific
example of photoperiodism.
 Flowering response (three
separate groups):
Long-day plants (e.g., beet
and clover).
Short-day plants (e.g.,
chrysanthemum and
ragweed).
Neutral plants (e.g.,
sunflower and tomato)
http://ashoutinthestreet.files.wordpress.com/2009/06/beet.j
pg
http://wendyusuallywanders.files.wordp
ress.com/2009/07/4-leaf-clover.jpg
http://www.discoverplants.com/planttypes/flowers/chrysanthemum/pictures/chrysanthe
mum-01.jpg
http://weeds.cropsci.illinois.edu/images/Commo
n%20ragweed/images/Common%20ragweed%
20vegetative%20plants.jpg
Photoperiodism Continued…
 Span of continuous
darkness is crucial.
 Short-day plants
should be exposed to a
minimum period of
darkness.
 Long-day plants have a
maximum limit on the
period of darkness
consistent with
flowering.
http://image.tutorvista.com/content/plant-growth-movements/photoperiodismlong-day-short-day-plants.jpeg
H.A. Borthwick and S.B.
Hendricks
 Discovered that red light (660 nm) and far-red light ( 730 nm)
were most effective in mediating photoperiodicity.
 Red light effects:
Most effective in interrupting the minimal period of darkness
required for short-day plants.
Most effective component in inducing light exposure in long-day
plants.
 Far-red light has the exact opposite effects as red light.
Phytochrome
 Borthwick and Hendricks hypothesized that this could be
best explained by the existence of a single pigment that
acts as a light receptor.
 This pigment, which they named phytochrome, must
exist in two forms.
Pr: absorbs red light.
Pfr: absorbs far-red light.
 Recent research suggests that phytochrome is a
conjugated protein.
Initial Synthesis of Phytochrome
 When Pr absorbs red light, it is converted to Pfr form.
 Pfr will absorb light in the far-red to reconstitute the
more stable Pr molecule.
 Pfr will revert to Pr in the dark.
 Most of the phytochrome exists as Pfr in the light.
 At night, Pfr levels are low.
 Two forms of pigment enable the plant to distinguish
between day and night.
Duration of Night or Day Periods
 The determination of the duration of night or day
periods in plants by the plant is more complex.
 Likely involves an interaction between
phytochrome and an internal clock mechanism.
 Biological clocks: exist as endogenous (internal)
rhythms of fairly intense activity and usually follow
a circadian (24-hour) cycle.
 The phyochrome system functions to mark dark
and light period, but does not provide the
measure of duration.
Biological Clock
 Biological clock effects:
Membrane function.
Permeability
characteristics of the
membrane.
Metabolism.

Related to alterations in
protein structure.

Change
concentration/characteri
s-tics of phospholipids
of the membrane.
http://www.cartoonstock.com/newscartoons/cartoonists/rma/lowres/rman5560l.jp
g
Plant Diseases
 All plants require water,
light, and a variety of
nutrients optimum
growth and
development.
 The short supply or
absence of any of these
factors challenges the
survival of the plant.
 If plants are grown
without light, they are
said to be etiolated.
http://www.uwsp.edu/biology/courses/botlab/images/Lab12Growth/12D%20
etiolate.jpg
Chlorosis
http://plantpath.wsu.edu/whatsnew/images/Pre%202006%20images/IW000032.jpg
 Take on a yellowish hue when the fail to form
chlorophyll in sufficient amounts.
 Arises from short supplies of mineral nutrients in
the soil.
 Iron shortages are a major cause as well.
Ergot
 A bizarre social
phenomenon is sometime
elicited by a fungus (ergot)
that attacks such monocot
crops as wheat, rye, barley,
and malt.
 Produces mind-altering
products if ingested by
humans.
 Mass waves of psychosis
(ergotism) swept through
Europe during the Middle
Ages and have occurred
more recently.
 Ergotate (a derivative of
ergot) is used as a
vasoconstrictor to control
bleeding, help treat
migraine headaches, and
stimulate uterine
contractions.
http://www.botany.hawaii.edu/faculty/wong/BOT135/ErgotonRye.gif
Wheat Rust
http://www.sciencedaily.com/images/2007/11/071126151723.jpg
http://www1.fccj.cc.fl.us/dbyres/images/rust100.jpg
 Puccinia graminis
 Affects wheat crops worldwide.
Mosaic Disease
 Mosaic virus is caused by a
variety of viruses which
attack and can destroy many
vegetable and fruit crops.
 If infected plants are not
cleared from the garden the
disease will spread.
 Aphids and cucumber beetles
spread the disease as they
feed going from infected plant
to healthy plant.
 Spraying has been
reasonably successful in
stopping the spread of some
of these infectious diseases.
http://www.aragriculture.org/images/diseases/image_library/
Tomato_Vegetables/squash/V20b_Squash.jpg
Developmental Abnormalities
 Plants exhibit
developmental
abnormalities.
 Are particularly evident in
tissue cultures.
 When plants are wounded,
they often develop masses
of amorphous material with
very poor cellular
differentiation known as
calluses.
 Plant tumors and cancers.
http://mbbnet.umn.edu/firsts/plant-gen.jpeg
http://www.rense.com/general82/agrobacterium.jpg
Galls
http://www.plantanswers.com/Oak_leaf_galls2.j
pglg.jpg
http://www.elkhornslough.org/journal/jour
nalpix/050908wasp-galls1.jpg
http://www.wildliferanger.com/users/www.w
ildliferanger.com/upload/Silk%20Button%2
0Spangle%20Galls%20001%20249.JPG
 Growth on a plant that are
induced by parasites and are
usually highly organized.
Crown Galls
 Are tumors caused by
bacteria.
 They are usually less well
differentiated than other
types of galls.
http://www.sactorose.org/ipm/22bacteria/2
2bacterialcrowngall-stem.jpg
Infectious Diseases
 Infectious diseases of plants may arise from
infestation from viruses, bacteria, or fungi.
 Serious economic effects.
 Large-scale death and starvation.
 Ireland mid-1840s fungal blight that destroyed
that potato crop (~1 million people died).
 Mainly responsible for the mass emigration of
Irish people to the United States.
References
 Fried, George and Hademenos, George.
Schaum’s Outline to Biology. New York: McGrawHill, 2009>