Leaves and the Use of MicroscopesUnit 1 - Biology

What is Biology?

Biology – 2 Greek wordsBios = life-logy = study of

So biology means….Study of life

Three Major Fields of BiologyBotany – 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 livingThe food you eat is/was livingYou are surrounded by living

things

BOTANYVascular 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 Plant1. Flowers – the reproductive part of

the plant. 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

1. Flowers2. Leaves – the food factory of

most plants. Leaves go through

photosynthesis to produce sugar for the plant.

There are many different types of leaves.

Parts of a Plant1. Flowers2. Leaves 3. Stems

Holds up the leaves and flowers.

It also transports substances and can transport food.

Parts of a PlantThere are four main groups of plants based on the type of stem:1.Tree – single, tall, woody stem

Parts of a PlantThere are four main groups of plants based on the type of stem:1.Tree2.Shrub – several low woody stems

Parts of a PlantThere are four main groups of plants based on the type of stem:1.Tree 2.Shrub3.Herb – non-woody plant (herbaceous stem)

Parts of a PlantThere are four main groups of plants based on the type of stem:1.Tree 2.Shrub 3.Herb 4.Vine – woody or herbaceous; grows along the ground or has tendrils that help it climb

Parts of a Plant1. Flowers2. Leaves 3. Stems4. Roots –

Anchors the plant into the ground.

It absorbs water and nutrients for plant growth

Stores food.

Parts of a PlantThere are two types of root systems:1.Taproot system – the primary rootgrows straight down and stays larger than secondary roots (ex: carrot, dandelion)

Parts of a PlantThere 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 LeavesSpecial 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 LeavesSpines – on cacti; lack chlorophyllLeaves of Venus flytrap, sundew,

pitcher plant, bladderwort – designed to trap and digest insects

Special StemsSome stems are mistaken for roots because of their location.Stolons – runners that aid in asexual reproduction (strawberries)

Special StemsSome stems are mistaken for roots because of their location.Rhizomes – horizontal stems that grow underground (ginger, iris)

Special StemsSome stems are mistaken for roots because of their location.Tubers – swollen ends of rhizomes that store food (potatoes)

Special StemsSome 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 HierarchyMoleculesCellsTissuesOrgansSystemsOrganism

Plant HierarchyMolecules – C, H, N, O + othersCells – Plant cells with differing

organellesTissues – Structural, vascular,

meristematicOrgans – Leaf, stem, flower, rootSystems – Root and ShootOrganism – Plant

Plant SystemsWhat is a system?

A group of structures designed to function together as a unit to perform a particular job for the organism.

Plant Systems2 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 leaf-like structure that covers a leaf as it is growing

Three Basic Leaf Types

1. Broad, flat leaves: roses, dandelions, maples, lilacs

2. Long, narrow leaves: grasses, lilies, onions, palms

3. Needle-like or scale-like leaves: pines, firs, cedars, spruces

Variety in Leaf ShapesBroadleaf leaves can

be oval, elliptical, heart-shaped, arrow-shaped, 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 MarginsThree main types of

leaf margins are:1. Entire – smooth

and unbroken2. Toothed – small

or large “teeth”3. Lobed –

extensions that stick out

Simple vs. Compound LeavesSimple 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)

OppositeOpposite – when 2

leaves grow from the same node

Attach at right angles to the leaves directly above and below them

Ex: maple, mint, coleus

AlternateAlternate – 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 VenationVenation = pattern of veins in a

leaf

1. Parallel2. Pinnate – one

major vein with smaller veins extending

Leaf Venation

Venation = pattern of veins in a leaf

1. Parallel 2. Pinnate 3. Palmate – 2 or more major

veins extending outward from one point

Evergreen vs. DeciduousEvergreen – foliage remains green year-

round

Evergreen vs. DeciduousDeciduous – sheds leaves annually

Evergreen vs. DeciduousConiferous – bears cones; usually

evergreen

Some examples of deciduous conifers: bald cypress, European larch, ginkgo

Evergreen broadleaf trees also exist, normally in the tropics.

PhototropismTropism = a plant’s response to

external stimuliIndividual 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.

PhototropismThis movement is an example of phototropism – the growth response of a plant stimulated by light

Phototropism

Other TropismsSome 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 TropismsGeotropism – 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 StructureMost cells have three basic parts.Cell membrane – Separates the

inside of a cell from the outsideNucleus – Controls activities in the

cellCytoplasm – A mixture of fluid and

organelles between the nucleus and the cell membrane

Cell StructurePlant 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)

PHOTOSYNTHESISand

CELLULAR RESPIRATION

Video

PhotosynthesisPurpose – 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

lightcarbon dioxide + water glucose + oxygen

54 photons lightCO2 + H20 C6H12O6 + O2

54 photons light6CO2 + 6H20 C6H12O6 + 6O2

Leaf Practice

Two Phases of Photosynthesis

Light Phase – Requires lightDark Phase – Doesn’t require

light, but can happen in the light

Light PhaseSolar 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 PhaseEnergy 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 Phase2 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 waterTemperature extremes (ph.

occurs best at 32-95o F)Poor light intensityShortage of carbon dioxide

Stages of SugarGlucose – form of sugar as it is made in a

plantSucrose – 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 RespirationCellular 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 oxygenGives off carbon, water, and energyThree parts: glycolysis, Krebs cycle,

electron transport chain

GlycolysisOne 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 formedHigh energy electrons are also

produced

Electron TransportThe electrons are used to

convert ADP into ATP

TotalsOne 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 ANDWILTING

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 PigmentsWhen the chlorophyll deteriorates,

other pigments that were hidden by the chlorophyll are now able to be seen.Chlorophyll – green colorsXanthophyll – yellowish colorsCarotene – yellowish-orange colorsAnthocyanin – bright red, blue, and

purple colors

Falling LeavesThe enzyme cellulase weakens the

cell wall of the abscission layer.The leaf will break off under its own

weight or with the help of windA protective layer of cork cells forms

at the base of the petiole producing the leaf scar on the branch

Water and WiltingNot all water taken in by the

plant is used. Much of it escapes through

transpiration

Water and WiltingFactors that affect the rate of

transpiration:HumidityTemperature Intensity of sunlightWind speedAmount of CO2 in the airAmount of soil water available

Water and WiltingThe guard cells are important in

controlling the rate of transpirationWhen 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

WiltingTranspriationWilting 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.

WiltingIn 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.