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Leaves and the
Use of
Microscopes
Unit 1 - Biology
What is Biology?
Biology – 2 Greek words
Bios = life
-logy = study of
So biology means….
Study of life
Three Major Fields of
Biology
Botany – study of plants
Human Anatomy and Physiology –
study of the structure and function of
the human body
Zoology – study of animals
Why Study Biology?
You
are living
The food you eat is/was living
You are surrounded by living
things
BOTANY
Vascular Plants
Why Study Botany?
All
of our food comes from
plants (~2/3 directly from plants
and ~1/3 from animals who eat
plants)
Many drugs and antibiotics
used in medicines come from
plants
Many plants and plant
products are vital to industry
Parts of a Plant
Flowers – the reproductive part of
the plant.
1.

Not all plants have showy flowers
and some plants don’t have any
flowers at all. Most plants with
flowers will produce fruit and seeds.
Parts of a Plant
Flowers
Leaves – the food factory of
most plants.
1.
2.


Leaves go through
photosynthesis to produce
sugar for the plant.
There are many different types
of leaves.
Parts of a Plant
Flowers
Leaves
Stems
1.
2.
3.


Holds up the leaves and
flowers.
It also transports substances
and can transport food.
Parts of a Plant
There are four main groups of
plants based on the type of
stem:
1.
Tree – single, tall, woody stem
Parts of a Plant
There are four main groups of
plants based on the type of
stem:
1.
2.
Tree
Shrub – several low woody stems
Parts of a Plant
There are four main groups of
plants based on the type of
stem:
1.
2.
3.
Tree
Shrub
Herb – non-woody plant
(herbaceous stem)
Parts of a Plant
There are four main groups of
plants based on the type of
stem:
1.
2.
3.
4.
Tree
Shrub
Herb
Vine – woody or herbaceous;
grows along the ground or has
tendrils that help it climb
Parts of a Plant
Flowers
Leaves
Stems
Roots –
1.
2.
3.
4.



Anchors the plant into the ground.
It absorbs water and nutrients for
plant growth
Stores food.
Parts of a Plant
There are two types of root systems:
Taproot system – the primary root
grows straight down and
stays larger than secondary
roots (ex: carrot, dandelion)
1.
Parts of a Plant
There are two types of root systems:
2. Fibrous root system –
the primary root remains
small and many
secondary roots grow
out in all directions
(ex: grass)
Special Leaves
Special
leaves have a special design
for a specific task. These are
considered leaves because buds
appear by them and they have the
same tissue structure of leaves.
 Tendrils
– special leaves that
coil around support structures
Special Leaves
Spines
– on cacti; lack chlorophyll
Leaves of Venus flytrap, sundew,
pitcher plant, bladderwort –
designed to trap and digest insects
Special Stems
Some stems are mistaken for roots because
of their location.
 Stolons – runners that aid in asexual
reproduction (strawberries)
Special Stems
Some stems are mistaken for roots because
of their location.
 Rhizomes – horizontal stems that grow
underground (ginger, iris)
Special Stems
Some stems are mistaken for roots because
of their location.
 Tubers – swollen ends of rhizomes that
store food (potatoes)
Special Stems
Some stems are mistaken for roots because
of their location.
 Bulbs – vertical underground shoots that
store food (onions)
The External
Structure and
Function of
Leaves
Organism Hierarchy
Molecules
Cells
Tissues
Organs
Systems
Organism
Plant Hierarchy
 Molecules
– C, H, N, O + others
 Cells – Plant cells with differing
organelles
 Tissues – Structural, vascular,
meristematic
 Organs – Leaf, stem, flower, root
 Systems – Root and Shoot
 Organism – Plant
Plant Systems
What is a system?
A group of structures designed
to function together as a unit to
perform a particular job for the
organism.
Plant Systems
2 types of systems:
1. Root system – the part of the
plant ordinarily under ground;
organ involved - roots
2. Shoot system – the part of the
plant which is usually found
above the ground; organs
involved – stem, leaves, flower
Leaf Parts
 Blade
– flat, green
portion of the leaf
 Petiole – leaf stalk
(leaves that lack a
petiole are sessile
leaves)
 Margin – edge of a
leaf
 Vein – carry sap
through a plant
 Stipule – small leaflike structure that
covers a leaf as it is
growing
Three Basic Leaf Types
1.
2.
3.
Broad, flat leaves: roses,
dandelions, maples, lilacs
Long, narrow leaves: grasses,
lilies, onions, palms
Needle-like or scale-like
leaves: pines, firs, cedars,
spruces
Variety in Leaf Shapes
 Broadleaf
leaves
can be oval,
elliptical, heartshaped, arrowshaped, oblong,
ovate, and many
other types
 Needle-like leaves
can be singular or in
bundles. This is an
important feature to
use to identify them.
Variety in Leaf Margins
Three main types of
leaf margins are:
1. Entire – smooth
and unbroken
2. Toothed – small
or large “teeth”
3. Lobed –
extensions that
stick out
Simple vs. Compound Leaves
 Simple
leaves have
one blade on every
petiole
 Compound leaves
have more than
one blade on every
petiole
 Compound
leaves
can have a variety
of arrangements
Leaf Arrangements
Leaves
are arranged so that all
leaves on a stem will have
maximum exposure to sunlight
Leaves have many different
arrangements.
(Vocab– a node is the point where a leaf
grows from the stem)
Opposite
Opposite – when 2
leaves grow from
the same node
Attach at right angles
to the leaves
directly above and
below them
Ex: maple, mint,
coleus
Alternate
Alternate – only 1 leaf
grows from each
node
The leaves alternate
sides as they go up
the branch.
Ex: apple, oak, birch
Whorled
Whorled – three or
more leaves grow
from each node
Ex: loosestrife, Easter
lily
Rosette (Basal)
Rosette – cluster of
leaves grow around
the base of the
plant
Usually a plant with a
rosette
arrangement
doesn’t have a
stem
Ex: dandelion
Leaf Venation
Venation = pattern of veins in a
leaf
1.
Parallel – veins are parallel to
each other
Leaf Venation
Venation = pattern of veins in a
leaf
1.
2.
Parallel
Pinnate – one
major vein
with smaller
veins extending
Leaf Venation
Venation = pattern of veins in a
leaf
1.
2.
3.
Parallel
Pinnate
Palmate – 2 or more major veins
extending outward from one
point
Evergreen vs. Deciduous
Evergreen – foliage remains green yearround
Evergreen vs. Deciduous
Deciduous – sheds leaves annually
Evergreen vs. Deciduous
Coniferous – bears cones; usually evergreen
Some examples of deciduous conifers:
bald cypress, European larch, ginkgo
Evergreen broadleaf trees also exist,
normally in the tropics.
Phototropism
Tropism
= a plant’s response to
external stimuli
Individual leaves will orient
themselves so that each blade is at
approximately a 90o angle to the
light. The petiole twists because there
is more growth on the side that
doesn’t have the light.
Phototropism
This movement is an example of
phototropism – the growth response
of a plant stimulated by light
Phototropism
Other Tropisms
Some other common plant tropisms:
Hydrotropism – response to water
(roots grow toward water)
Thigmotropism – response to touch
(ex: vines wrap around a pole,
sensitive plant)
Other Tropisms
Geotropism – response to gravity;
can be positive or negative
(positive – roots grow down;
negative – stem grows up)
Heliotropism – sun-tracking (ex:
sunflowers)
Leaf
Anatomy
(WKST)
Cell Structure
Most cells have three basic parts.
 Cell membrane – Separates the
inside of a cell from the outside
 Nucleus – Controls activities in the
cell
 Cytoplasm – A mixture of fluid and
organelles between the nucleus
and the cell membrane
Cell Structure
Plant cells have some components that are
not found in animal cells.
 Cell wall – A rigid layer outside the cell
membrane that gives structure to a plant
cell; made of cellulose
 Chloroplasts – Contain the pigment
chlorophyll; absorb energy from the sun for
photosynthesis
 Vacuole – A storage area inside of the cell
(found in some animal cells)
PHOTOSYNTHESIS
and
CELLULAR
RESPIRATION
Video
Photosynthesis
Purpose – Make food for the plant
Occurs – in the chloroplasts
Photosynthesis – “putting together with light”
All plants that go through photosynthesis have
chloroplasts regardless of their color.
Photosynthesis takes place in the
chloroplasts.
It’s estimated that plants produce 300 billion
tons of food each year.
Formula for Photosynthesis
light
carbon dioxide + water
glucose + oxygen
54 photons light
CO2 + H20
C6H12O6 + O2
54 photons light
6CO2 + 6H20
C6H12O6 + 6O2
Leaf Practice
Two Phases of Photosynthesis
Light Phase – Requires light
Dark Phase – Doesn’t require
light, but can happen in the
light
Light Phase
Solar
energy is converted into
the chemical energy of ATP
and NADPH.
Chlorophyll absorbs the solar
energy. Water, ADP, and
NADP are ingredients for the
reaction.
ATP, NADPH, and oxygen are
the products.
Light Phase
Energy
from the sun splits the
water molecule into hydrogen
and oxygen.
Hydrogen connects with NADP
to form NADPH.
Oxygen will later be released.
ATP and NADPH store energy.
Dark Phase
Happens
in the light, but
does not require light
energy
The dark phase is known as
the Calvin cycle
Dark Phase
2
3-carbon molecules
combine to make glucose.
C and O come from the
carbon dioxide. H comes
from the NADPH.
The energy to do this
comes from ATP breaking
down into ADP.
What Affects
Photosynthesis?
Shortage
of water
Temperature extremes (ph.
occurs best at 32-95o F)
Poor light intensity
Shortage of carbon dioxide
Stages of Sugar
 Glucose
– form of sugar as it is
made in a plant
 Sucrose – form of sugar as it is
transported; formed by glucose
and fructose molecules attached;
this is why sap tastes sweet
 Starch – form of sugar as it is stored;
complex carbohydrate; many sugar
molecules are joined together
* Fructose – same chemical formula
as glucose, but arranged differently
Cellular Respiration
 Cellular
respiration is the process by
which food energy is released in the
presence of oxygen
 This occurs in the mitochondria
 In plants, requires glucose and
oxygen
 Gives off carbon, water, and
energy
 Three parts: glycolysis, Krebs cycle,
electron transport chain
Glycolysis
 One
molecule of glucose is broken
into two 3-carbon molecules of
pyruvic acid
 2 molecules of ATP provide the
energy
 4 molecules of ATP end up being
produced
Krebs Cycle
 In
a series of reactions, pyruvic acid
is broken down into carbon dioxide
 NADH, FADH2, and ATP are formed
 High energy electrons are also
produced
Electron Transport
The
electrons are used to
convert ADP into ATP
Totals
 One
glucose molecule can produce 36 ATP
molecules after it goes through cellular
respiration
 Without oxygen, glucose can only produce
2 ATP molecules during glycolysis and none
during the Krebs cycle and electron
transport (without oxygen, cells complete
either alcoholic fermentation or lactic acid
fermentation)
FALL
COLORATION
AND
WILTING
Why Do Leaves Turn Colors?
 The
changes in the fall are triggered
by the change in daylight.
 The abscission layer forms between
the base of the petiole and the
stem.
 This prevents materials from being
able to go in and out of the leaf.
 This causes the chlorophyll to begin
to deteriorate.
Plant Pigments
 When
the chlorophyll deteriorates,
other pigments that were hidden by
the chlorophyll are now able to be
seen.
 Chlorophyll
– green colors
 Xanthophyll – yellowish colors
 Carotene – yellowish-orange
colors
 Anthocyanin – bright red, blue,
and purple colors
Falling Leaves
 The
enzyme cellulase weakens the
cell wall of the abscission layer.
 The leaf will break off under its own
weight or with the help of wind
 A protective layer of cork cells forms
at the base of the petiole
producing the leaf scar on the
branch
Water and Wilting
Not
all water taken in by the
plant is used.
Much of it escapes through
transpiration
Water and Wilting
Factors
that affect the rate of
transpiration:
 Humidity
 Temperature
 Intensity
of sunlight
 Wind speed
 Amount of CO2 in the air
 Amount of soil water available
Water and Wilting
 The
guard cells are important in
controlling the rate of transpiration
 When there is a lot of water in the
plant, the guard cells become
turgid and the stoma opens
 When water is moving out of the
guard cells faster than it can be
replaced, the guard cells close the
stoma
Wilting
 Transpriation
 Wilting
occurs when more
transpiration is occurring than water
getting into the plant.
 Temporary wilting may occur on a
hot day when a plant is in the sun.
The sun causes more water to be
lost than the plant can get from its
roots. When the plant is in the
shade, it is able to catch up and
the cells become turgid again.
Wilting
In
permanent wilting, there is
usually a drought or poor
retention of soil water so the
plant cannot replace any of
the water lost through
transpiration.