Plant function slides

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Plant Function

AP Biology Rapid Learning Series
Wayne Huang, PhD
Andrew Graham, PhD
Elizabeth James, PhD
Casandra Rauser, PhD
Jessica Habashi, PhD
Sara Olson, PhD
Jessica Barnes, PhD

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© Rapid Learning Inc. All rights reserved.

© Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com

1


Learning Objectives
By completing this tutorial, you will learn about:

Plant N t iti
Pl t Nutrition
Plant Hormones
Plant Defense
Plant Reproduction

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Plant Function Concept Map
Plant Growth

Soil

Air

Plant reproduction

Regulated by
Flower structure

Insects
pathogens

Plant Hormones
Seed Development

Auxin

ABAs

Cytokinins
GAS

Ethylene

Phototropism
Growth promotion
Gravitropism
Apical Dormancy
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2


Plant Nutrition
Plants obtain their nutrients from soil and air.

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Plant Nutritional Sources
The major source of plant
nutrition is fixation of
atmospheric CO2 using
photosynthesis to produce
simple sugar
sugar.

Photosynthesis is the source
of energy to make sugars.

Soil and water are
also sources of
nutrition. They
provide an
anchorage as well as
minerals and
nutrients.
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3


Nutrient Classes
Nonmineral nutrients from
air and water, carbon,
hydrogen and oxygen.
oxygen

Mineral nutrients from soil
include macronutrients
which are required in large
quantities.

Micronutrients are
required in small
quantities.
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Macronutrients
Primary macronutrients
include: nitrogen,
phosphorus and
potassium.

Secondary macronutrients
include: calcium, magnesium
and sulfur.

Potassium

Calcium
Nitrogen

Magnesium

Sulfur

Phosphorus

Secondary
Primary

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4


7 Micronutrients
There are 7 micronutrients. These
are needed in small amounts.

Copper (Cu)

Iron (Fe)

Zinc (Zn)

Boron (B)
Molybdenum (Mo)

Chloride (Cl)
Manganese (Mn)

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Obtaining Nutrients
Macronutrients are
usually not sufficient in
cultivated soil and need
to be added as fertilizer.

Plants get nutrients
from soil (roots) or air
(leaves and stems).

Natural plant communities
recycle nutrients for use
by other organisms.

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•
•
•
•

Other ways to get nutrients include:
Nitrogen fixation by bacteria.
Carnivorous feeding.
Symbiotic association with fungi.
Parasitic plants.


5


Transpiration
Transpiration is the evaporation of
excess water from aerial parts of a
plant. This is done by leaves,
stems, flowers and fruits.
Root absorbs minerals
and water from soil
Water and solute are
transported up through
plants via xylem
The driving force is the
evaporation from leaves
via guard cells
This process is called
transpiration
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Transportation of Carbohydrates
Leaves make
y
carbohydrates to
support plant life –
sugar source
Carbohydrates are
transported down via
phloem in vascular
tissue to where they
can b used –sugar
be
d
sink

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6


Plant Hormones
Plant Growth and Development

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Plant Hormones
Five major types of hormones that control plant growth and
development.

1. Auxin
2. Gibberellins
(GA)
3. Cytokinins
4. Ethylene
5. Abscisic
Acid (ABA)

A hormone is a chemical
messenger between
cells. They signal target
cells to change a
physiological activity.

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7


Auxin
Auxins are produced by apical
tissues and developing leaves
and they stimulates downward
growth.

Auxins function at the cell
level by stimulating cell
elongation and cell division.

The most important auxin
is indole-3-acetic acid
(IAA).

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Auxin Functions
Auxins are plant hormones that are
Auxin
involved in the coordination of many
growth and behavior processes in
the plant s life cycle.
plant’s
cycle
Auxins are used to promote
the growth of roots as
well as flowering, setting
fruits and preventing
p
premature fruit drop.
p

Auxins act by stimulating or
inhibiting the expression
of specific genes.
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8


Apical Dominance
Apical dominance is
the inhibition of
lateral buds by auxin
from the apical bud.

Dormant
lateral bud

Auxin is broken
down as it moves
down stem, so its
concentration
decreases.

Apical bud removed

Removal of apical
bud releases apical
dominance

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Phototropism
Phototropism: when
illuminated from one
direction, the shoot
proceeds to grow in that
direction.
When illuminated, Auxin
accumulates on the shady
side of a plant
g
This stimulate elongation of
cells from the shady side
and bend the plant to the
light

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9


Gravitropism
Plant growth and its movements
respond to gravity. This is
known as gravitropism.

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When a plant is put into a
horizontal position plant
shoots will bend upward
because auxin accumulates
on the lower part of the stem
called negative gravitropism.

Plant roots will respond by
bending down which is known
as positive gravitropism. This
is because of the accumulation
of starch granules in the root
caps.

Cytokinins – Adenine Derivatives
Cytokinins stimulate plant cell
differentiation. Notice the
difference in these two plants of
treated versus untreated.

•
•
•

•
•

Cytokinin Function
Stimulate cell division
Major source: roots
and apical meritstem
Opposite to auxin:
1)Move up a d; 2)
) o e upward; )
promote growth of
lateral buds
Prevents leaf
senescence
Essential for plant cell
culture.

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10


Gibberellins
Gibberellins promote stem elongation, as
well as in “bolting” which is sudden stem
elongation. It breaks the dormancy of seeds
and stimulates flowering mature plants.
plants

There are more than
30 structurally
related compounds.
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Abscisic Acid
It is a major plant stress
hormone. Abscisic acid is a
plant hormone involved in
adscission (shedding) of plant
y
parts and in bud dormancy.

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Abscisic acid is involved in the
closing of stomata. It inhibits
fruit ripening and encourages
seed dormancy by inhibiting cell
growth.

In winter preparation
abscisic acid is produced in
the terminal buds and slows
growth and protects buds
during the cold.


11


Ethylene
The only gas form of plant hormone, produced by fruit.

Function
Promote fruit ripening
Stimulates senescence
and abscission in leaves
and fruits
Minor functions:

H2C=CH2

Ethylene

Sprouting of potato buds;
p
g p
;
Seed germination;
Flower formation in some
species

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What Plant Hormone Trigger Growth?
Do you know what plant
hormone is involved in
p
promoting growth?
gg

If you said auxin,
cytokinin and
gibberellins you are
right.

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12


Plant Defense
How plants cope with stress and insects

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Plant Defense
There are two basic
strategies of plant
defense: physical and
chemical barrier.

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Physical barriers against
herbivores include:
• Cuticle: a layer of wax on
the surface of leaves
• Trichomes: extension of
plant cells
• Spines which are modified
leaves.
• Bark

Chemical barriers: secondary metabolites or chemical
toxins that could cause problems for the predator.
These chemicals include isoprenes, phenolic
compounds and alkaloids.


13


Systemin Response
Plant response to wound: systemin

Synthesis f
S th i of
Systemin

Synthesis f
S th i of
Proteinase inhibitors

Plants under attack

Systemin is a signal molecule for plants to sense the wound and
triggers a series of biochemical reaction to release proteinase
inhibitors which are toxic to insects.

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Plant Defense to Pathogens
Virus
Infection
Cell Death
Hypersensitive
Response (HR)

■ Gene-for-Gene Theory
To every pathogen avirulence (avr) gene, there is a
corresponding R gene (resistance gene) in plant to trigger
HR
HR is commonly followed by a slower response that leads
to systemin acquired resistance (SAR). SAR occurs when a
hormone, which may be salicylic acid, travels from the
infection site to nearby tissues and triggers the expression
of a specific set of genes.
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14


How Does a Plant Respond to Injury?
How do plants
respond to being
wounded?

It mounts a systemin
response involving
signaling from
systemin.

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Plant Reproduction

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15


Sexual and Asexual Reproduction
Plants can reproduce
asexually and sexually.

Yes, sexual reproduction involves
male gametes (sperms) and female
gametes (eggs) which combine to
create a zygote.

In asexual reproduction
offspring are produced
by mitosis and are
genetically identical to
the parent.

Female structures
house the embryo
during development.
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Life Cycle of a Flowering Plant

Seed production
Seeds

Seed germination

Adult plant
with flowers
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Pea plant


Seedling

16


Flowers are Reproductive Organs
Stigma

Pedal

Ovary

Carpel
(female organs)

Anther
Filament

Steman
(male organs)

Sepal

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Formation of Gametes
Microspores -->
Pollens

Mother Cell (2N)
Meiosis

Megaspores --> Eggs
Pollen
Mother Cell

1N
2N

Meiosis
Pollen
Grain

Pollen
Grain

Pollen
Grain

Pollen
Grain

1N
Pollen grain in anther

3
megaspores
degenerate, 1
survives
3 times mitosis
then cell dividing
1N egg cell
2N central cell
t l ll
1N egg cell
Embryo sac in ovary

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17


Pollination
Pollination: Pollen from male organs are transferred to
surface of stigma
Sperms meet megaspores (eggs)
1

Self-pollination
Self-pollination,
same plant but
different flower

2

3

p
Cross-pollination
Different plants

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Formation of Zygotes
Pollen tube grows, two sperm cells are delivered into ovary
One sperm fertilize one of the 6 eggs, one fertilizes the central
cell
Fertilized egg develops into 2N zygotes and fertilized central
cell develop into endosperm (3N)
Zygotes attach to parental plant to acquire nutrients which is to
be stored in cotyledons
Ovary
3N
1N

1N
1N

Central cell (2N)

1N

1N

Egg cell (1N)

3N

1N

3N
3N

Endosperm
(3N)
Embryo (2N)

2 sperm nuclei
Pollen tube

Double pollination
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18


Seed Structure
Zygotes grow and differentiate, acquiring and
store food in cotyledons and seed forms.

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How are Seeds Developed?
Double pollination.
Pollination of eggs forms
the embryo.

How does a seed
develop?

Acorn

Pollination of the central cell
forms the endosperm
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19


Question: Review
____ is the evaporation of
excess water from aerial parts
of a plant.
Auxins ti l t
A i stimulate _____
growth.

Transpiration
___________
Downward
D
d
___________

_______ is the inhibition of
lateral buds by auxin from
the apical bud.

___________
Apical dominance

_____ stimulate plant cell
differentiation.

Cytokinins
___________

____ promote stem
elongation and bolting.

___________
Gibberellins

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Learning Summary
Plant defense

Plant nutrients

Natural barrier
Macronutrients
micronutrients

Against wound
Against pathogen

Plant reproduction
Flowers
Zygotes

Plant
Pl t growth and
th d
development
Plant hormones

Seeds
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20


Congratulations
You have successfully completed the
core tutorial

Plant Function

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Chemistry :: Biology :: Physics :: Math

What’s N t
Wh t’ Next …

Step 1: Concepts – Core Tutorial (Just Completed)
Step 2: Practice – Interactive Problem Drill
Step 3: Recap – Super Review Cheat Sheet

Go for it!

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