the world of plants std grade
TRANSCRIPT
INTRODUCING PLANTS
PLANTS - THE BASICS A huge variety of plants in the
world Live in almost every habitat Can survive the harshest
environments The link between the sun and all
other living things Maintain the balance of
atmospheric gases
MORE PLANT BASICS They regulate the water content
of the soil
They provide habitats for other organisms
And ……….
…. they give us some beautiful artistic moments!
VARIETY
MORE VARIETY
HABITATS
MORE HABITATS
PLANTS AND THE SUNPlants turn the sun’s energy ………
into food
This is called………. Photosynthesis
PLANTS ARE ALSO HABITATS
WHAT DO WE NEED PLANTS FOR ?
For food
For raw materials
For medicines
PLANTS AS FOODS Cereals such as rice,maize,and
wheat form the staple foods of most countries
Vegetables and fruits add variety to our diets
Herbs,spices,sugar,tea,coffee and nuts are all plantsand…… we get chocolate from plants !!!!!
…. IN SCOTLAND
Barley is used to make….
AND……
Plant-based dyes are used for…..
PLANTS AS MEDICINES Known about since 2000BC Used for pain relief, reducing fever,
sedation and upset stomach, and curing infections
Many are used for treating cancer
……And many more medicinal uses
PLANTS TREAT CANCERIt is thought that at least 2000 plants may contain chemicals which can help to treat cancer
This is the purple coneflower
PLANTS CLEAR YOUR HEAD
This is the titfruit. Its extract can clear blocked sinuses
MORE PLANT MEDICINES…Plants can be used for hormone replacement
This is squawberry juice being extracted
Plants can help with urinary infectionsThis is saw palmetto used for cystitis and Prostate problems in men
DO YOU KNOW THIS ONE ?
PLANTS AS MATERIALS Cotton for clothes and linens Jute and hemp for rope Trees for timber Rape seeds for oil Seaweeds for alginates
How many more can you think of ?
PLANTS ARE SO INTERESTING…..
These american native indians even worshiptheir cacti….
SO…… PLANTS ARE ?Much more complex and varied than you knew
“World of plants” will show you how
and why .
Ecological loss Tropical rainforests have the greatest
variety of plants on earth There loss is disastrous For every type of plant that becomes
extinct a wide variety of other dependent organisms are also endangered.
For every species of plant that becomes extinct,four species of animal also die out,upsetting the balance of life on earth
ENDANGERED SPECIES
FOOD PLANTS MOST OF THE WORLDS FOOD
COMES FROM A VERY FEW TYPES OF PLANTS
AS THE POPULATION INCREASES,THEN SOME OTHER TYPES OF PLANT WHICH ARE NOT WELL KNOWN MIGHT PROVIDE FOOD
EVEN FLOWERS !
MEDICINAL PLANTS Many important medicines come
from plants
In the future,possible medicines may never be discovered if the plants are made extinct by destroying the rainforests.
WILD PLANTS…… Wild plants also contain many different
characteristics ….and different genes which could be useful in the future.
….. So its important to protect the wild varieties for possible future use.
THIS IS CALLED A GENETIC STOREHOUSE
GENETIC STOREHOUSE Cultivated plants have been bred to be
very alike They contain almost exactly the same
genes If a new disease infected one,it could
easily damage all of them Wild varieties are often resistant to many
different diseases It is possible to cross-breed them with
cultivated plants to increase the resistance to disease
Seed Germination When spring arrives,the seed
bursts open and a new plant starts to grow
This is called GERMINATION
What’s in a seed ? Seeds usually have a hard coat. This is also called the TESTA It’s a tough,fibrous layer which
protects the internal structures of the seed
Lets have a look at the inside of a seed
Inside the seed This Broad bean
seed has been left to soak in water overnight.
This softens the seed coat and allows us to pull it away from the seed
You can now examine the internal structures of the seed
Structure of the mature seed
In dicot seeds:– Hypocotyl terminates in the
radicle (embryonic root)– Epicotyl terminates in the
plumule (shoot tip) Monocot seeds have a
special cotyledon called a scutellum:– Large surface area - absorbs
nutrients from endosperm during germination
– Embryo enclosed in sheath: Coleoptile protects the shoot Coleorhiza protects the root
Inside the Bean seed The inside of a seed is
called ….. The EMBRYO It’s made up of two
parts… The young shoot(called
the PLUMULE ) And the young root ( called the RADICLE)There is also a pair of seed
leaves (called COTYLEDONS) they act as a food store
The seed germinates First the seed takes up water.This
makes it swell The seed coat splits and the new plant
starts to grow out,root first Next,the shoot starts to grow. The root grows downwards ….. And the shoot grows upwards The shoot is bent back to protect its
delicate tip as it pushes up through the soil
…. The embryo starts to grow
You can see the root starting To grow downwards
Germination continues…. The root tip is protected from damage
as it grows down through the soil by a mass of cells called the Root Cap
The root grows tiny side branches to help anchor the young plant into the ground
These hairs also increase the surface area for absorbtion
…. The root grows hairs
We can see the root hairs starting to grow
Roots – function and structure
Hold plant in positionAbsorb water and minerals
from the soilSpecialised cells to increase
surface area for water intake
Wheat seed
Root hairs
Fragile parts of cells that grow from the main root
They massively increase the surface area for absorption
Root hair cells (x150)
Root ‘B’ has had the hairs damaged -
….and finally The young shoot
breaks through the soil surface
It straightens out The first leaves open
out and turn green Germination is
complete and the new plant is called a seedling
Factors affecting germination
Temperature. Warmth is needed by most seeds.This is why they don’t germinate until the spring
Water is needed for the seed to swell and burst open. It is also necessary for the stored food to be made soluble and moved to the growing embryo
Oxygen is needed for the embryo to respire.It supplies the embryo with the energy to grow and develop
What about light ? Most seeds will germinate in light or dark
conditions However some will only germinate in one
or the other. The amount of light needed may be very
small.One quick flash is enough in some cases
All plants need light once the shoot breaks through the surface of the soil. This is to make the leaves open out and form CHLOROPHYLL FOR PHOTOSYNTHESIS
CRESS SEEDS GERMINATING
REPRODUCTIONIN
FLOWERING PLANTS
Floral diversity
THEY ALL LOOK DIFFERENT…BUT ALL HAVE THESAME PARTS FOR REPRODUCTION…
The Parts of a Flower Most flowers
have four parts: sepals, petals, stamens, carpels.
The parts of a flower Sepals protect the
bud until it opens. Petals attract
insects. Stamens make
pollen. Carpels grow into
fruits which contain the seeds.
Stamen (male) Anther: pollen
grains grow in the anther.
When the grains are fully grown, the anther splits open.
Carpel(female) Stigma Style ovary Ovules (eggs)
Pollination Flowering plants
use the wind, insects, bats, birds and mammals to transfer pollen from the male (stamen) part of the flower to the female (stigma) part of the flower.
Pollination A flower is
pollinated when a pollen grain lands on its stigma.
Each carpel grows into a fruit which contains the seeds.
Fertilisation Pollen grains
germinate on the stigma, growing down the style to reach an ovule.
Fertilised ovules develop into seeds.
The carpel enlarges to form the flesh of the fruit and to protect the ovary.
The ovary develops into a fruit adapted for seed
dispersal A true fruit is a ripened
ovary Fruits can be classified
by their origin:– Simple fruits:
derived from a single ovary e.g. cherry
– Aggregate fruits: derived from a single flower with several carpels e.g. blackberry
BUT …WHAT ABOUT ‘FALSE FRUITS’ ?
Wind pollination Some flowers, such
as grasses, do not have brightly coloured petals and nectar to attract insects.
They do have stamens and carpels.
These flowers are pollinated by the wind.
Seed dispersalSeeds are dispersed
in many different ways:
Wind Explosion Water Animals Birds Scatter
How birds and animals help seed dispersal
Some seeds are hidden in the ground as a winter store.
Some fruits have hooks on them and cling to fur or clothes.
How birds and animals help seed dispersal
Birds and animals eat the fruits and excrete the seeds away from the parent plant.
ASEXUAL REPRODUCTION Plants can be produced by a single
parent No need for sex cells and fertilisation Because of this, there will be NO
variation and new plants formed will be….
GENETICALLY IDENTICAL to one another AND to their parent
Asexual reproduction in plants is known as VEGETATIVE PROPAGATION.
Methods of Artificial propagation…
Offspring can be formed from a plant’s stem or buds
These are known as RUNNERS
The runner carries food from the parent to the new plant whilst it grows leaves and roots
Strawberry and Spider plants are good examples ofSpecies which use RUNNERS for asexual reproduction
Some plants produce large swollen roots called TUBERS
These are food storage organs full of STARCH
A plant may produce several of these.
Each will produce a new plant which may make many more TUBERS
Examples of plants which use this method ofVEGETATIVE PROPAGATION include ….
Artificial Propagation Some plants lack their own natural methods
of artificial propagation These plants can be reproduced by
artificial processes. This can be done for several reasons… (1) uniformity is guaranteed (2) Sterile varieties can be reproduced in
vast quantities, such as seedless grapes and citrus fruits
(3) Rare species can be conserved to protect against extinction
TWO METHODS ARE COMMONLY USED……CUTTINGS AND GRAFTING.
…CUTTINGS
Stems and leaves are used to grow new plants
Roots form from the cutting when it is placed in good soil
REMEMBER….ALL CUTTINGS GROW INTO PLANTSWITH FEATURES IDENTICAL TO THEIR PARENT
GRAFTING A cutting (SCION)is
grafted onto the STOCK of a hardy variety as shown
The scion may come from a high yield fruiting plant
This method can combine the good qualities of TWO or more plants
The cut surfaces bond together, healing the wound whichIs protected from infection by being sealed with wax. TwineHolds the cut surfaces tightly together to promote healing
Are these plants clones YES…THEY ARE A CLONE is a
group of organisms which have exactly the same genetic info and have been produced from a common ancestor by ASEXUAL REPRODUCTION
So the term CLONE can be used to refer to a group of Plants produced from cuttings or graftings from the SAME PARENT PLANT
There are two film clips coming next They show cutting and grafting
taking place in the south of the USA Please be patient…they take a few
seconds to load You can only see them if you are
watching this presentation on a computer logged on to the internet
pinks_16x9_bb.ram
pecangrafting1.ram
Plant growthPlant growthPlants grow using food they make through
photosynthesis. So what else do they need?
Plants also need three important minerals to keep healthy. They absorb these through their roots.
Root hair cells
Plant roots are made of “root hair cells” which have a large surface area and a thin cell membrane to help absorb the minerals:
Thin cell membrane
Large surface area
Plant A Plant BBoth plants were planted at the same time and left to grow on the same window sill for the same length of time.
Why do you think that plant A is so much bigger than plant B?
How do plants get the minerals they need?
The plant takes in minerals from the soil. It absorbs these minerals through their
roots. Remember a plant does not get food from
the soil it is capable of making its own food
Some plants which grow on poor soil have evolved a clever way to get the nutrients they need.
Where do you think they get them from?
The three main types of nutrient are:The three main types of nutrient are:
1. Nitrates – used to make proteins
2. Phosphates – used to provide phosphorus to help photosynthesis and respiration
3. Potassium – helps the enzymes that are needed for photosynthesis and respiration
Lack of the three minerals would lead to a “Deficiency Symptom”:
Lack of nitrates:Small plant, yellow leaves
Lack of phosphates:Small roots and purple leaves
Lack of potassium:Yellow leaves with dead bits
The Three Main Minerals Needed by Plants.
Mineral Why its needed
Symptom if deficient
Nitrate To make proteins
A small plant with yellow older leaves.
Phosphate Needed for photosynthesis and respiration
Poor root growth and purple younger leaves
Potassium Helps chemicals in the plant work properly.
Yellow leaves with dead bits
Plant Doctor.1. Mr Smith’s plants were small and
had yellow leaves, which mineral were they missing?
2. Mr Lewis’s plants were a normal size but had yellow leaves, which mineral were they missing?
3. Mr Brooke had a plant which had some purple and some yellow leaves, which minerals were they missing?
The Transport System
There are a set of tube-like tissues that go up and down the leaf stem and shoots that transport the other essential ingredients for photosynthesis : water and minerals
There are two tubes called xylem and phloem tissues.
The Transport System
The xylem brings up the water from the roots
The phloem takes away the sugars made by the chloroplasts to places where the energy is needed
The tubes are in the middle of the leaf so that there are near all the cells to bring up water and to take away sugars.
The transport system The transport system is far less
elaborate than in mammals due to:– plants are less active and therefore
‘supplies’ don’t run out so quickly– because of the branching system,
gases for respiration and photosynthesis. Can be obtained from diffusion in the air
– two separate systems; xylem and phloem
Xylem Xylem carries the water and minerals It is made of many hollow dead cells joined
end to end of which the end cell wall has disappeared to form a long tube
Xylem vessels run from root to every leaf Xylem vessels contain no cytoplasm or nuclei Their walls are made of cellulose and lignin Lignin is very strong and so xylem help keep
the plant upright
Close up of Hibiscus rosa xylem
Phloem Transport the ‘food’ They are also made of many cells joined end
to end, however their end wall is not completely broken down; instead they form sieve plates
The cells contain cytoplasm but no nucleus and they do have lignin in their walls
Each sieve cell has a companion cell next to it which does contain a nucleus and many other organelles
Phloem tubes
Vascular bundles Xylem and phloem tubes are normally found
close together, when they are this is called a vascular bundle
In a root vascular tissue is found at the centre
In a shoot they are found near the outside edge to help support the plant
Transverse section of a stem
The transport of water Plants take in water from the soil through the
root hairs and is carried in the xylem throughout the plant
Water gets into root hair by osmosis. The cytoplasm and cell sap inside it are quite
concentrated solutions and the water in soil is normally quite dilute
Water therefore diffuses down its concentration gradient through a partially permeable membrane
A root tip showing root hairs
Transpiration The evaporation of water from the plant Most of which takes place from the leaves
through the stomata Guard cells around the stomata control the
rate of transpiration by opening and closing
Transpiration When water is lost through transpiration
water from the xylem vessel in the leaf will travel to the cells to replace it
Water is constantly being taken from the top of the xylem vessel to supply the cells in the leaves
This reduces the pressure at the top of the xylem so water flows up
This process is known as the transpiration stream
Leaves
THE LEAF! A leaf is an example of a plant
organ It is composed of many tissues
that work together. The tissues are designed to
maximise the levels of photosynthesis.
Function of leaves Trap light energy for photosynthesis
Producing sugar from photosynthesis
Exchange of gases – oxygen and carbon dioxide
Structure
Wide
Helps to catch more light energy
Thin
Help get carbon dioxide from bottom to top of leaf for photosynthesis
Leaf structure
Greener on top
CO2 gets in here
Leaf diagram – palisade layer
CO2
Most chlorophyll
Leaf cell - palisade
Position?Upper surface
of leafFeatures?
Box shapeChloroplasts
Function?Photosynthesis
Plant cells have three “extra” things Plant cells have three “extra” things than animal cells:than animal cells:
Both types of cell have these: Only plant cells have these:
4) Cell wall – provides support
Large Vacuole – contains sap
Chloroplasts – contain chlorophyll
1)
5)
6)
2)
3) Cell Membrane – holds the cell together
Cytoplasm - this is where the reactions happen
Nucleus – The “brain” of the cell
Gas exchange Leaves are designed to allow
carbon dioxide to get to the main chlorophyll layer at the top of the leaf
They have small holes called stomata on the under surface
Each hole is open & closed by 2 guard cells
Leaf diagram – stoma and guard cells
Stoma position
Stoma is a small holeIts size is controlled by 2 guard cells
closed open
Stoma function is for gas exchange in the leaf
Carbon dioxide
oxygenGuard cell
Provided plant is photosynthesising
Stomata open and close at different times of the day
When it is light the plant needs CO2 for photosynthesis so the stoma open
At night (darkness) they close
Gas exchange
PhotosynthesisPhotosynthesisA Photosynthesis is the process a
plant uses to make food and grow. The food produced is
GLUCOSE. This is a carbohydrate.They are made up of…CARBON, HYDROGEN, andOXYGEN.Glucose is SOLUBLE so thePlant has to convert it intoSTARCH which is INSOLUBLEOr CELLULOSE for buildingCell walls.
STARCH is a STORAGE carbohydrateCELLULOSE is a STRUCTURAL carbohydrate
Four things are needed for photosynthesis:
Travels up from the roots
WATER
CARBON DIOXIDE
Enters the leaf through small holes on the underneath
SUNLIGHT
Gives the plant energy CHLOROPHYL
L
The green stuff where the chemical reactions happen
The word and chemical equations for photosynthesis:
Carbon dioxide + water glucose + oxygen
6CO2 + 6H20 C6H12O6 + 6O2
Sunlight
Chlorophyll
Sunlight
Chlorophyll
Four factors affect Four factors affect photosynthesis:photosynthesis:
1. Light – if there is more light photosynthesis happens faster
2. Water – if there is not enough water photosynthesis slows down
3. Temperature – the best temperature is about 300C – anything above 400C will slow photosynthesis right down
4. CO2 – if there is more carbon dioxide photosynthesis will happen quicker
These are known as LIMITING FACTORS becauseLack of any one or more will slow down photosynthesis