Transcript Plant Cultivation SJF

What factors affect plant
growth?
LO- to explain the factors which affect
plant growth
What factors affect plant
growth?
LO- to explain the factors which affect
plant growth
Green plants absorb light energy using
chlorophyll in their leaves. They use it
to react carbon dioxide with water to
make a sugar called glucose. The
glucose is used in respiration, or
converted into starch and stored.
Oxygen is produced as a by-product.
During photosynthesis:
•Light energy is absorbed by chlorophyll, a green
substance found in chloroplasts in some plant cells
and algae
•Absorbed light energy is used to convert carbon
dioxide (from the air) and water (from the soil) into a
sugar called glucose
•Oxygen is released as a by-product
This equation summarises what happens in
photosynthesis:
Some glucose is used for
respiration, while some is converted
into insoluble starch for storage. The
stored starch can later be turned
back into glucose and used in
respiration.
Without enough light, a plant cannot
photosynthesise very quickly, even if there is
plenty of water and carbon dioxide. Increasing
the light intensity will boost the speed of
photosynthesis.
Sometimes photosynthesis is limited by the
concentration of carbon dioxide in the air. Even
if there is plenty of light, a plant cannot
photosynthesise if there is insufficient carbon
dioxide
If it gets too cold, the rate of photosynthesis will
decrease. Plants cannot photosynthesise if it gets
too hot.
If you plot the rate of photosynthesis against the
levels of these three limiting factors, you get
graphs like the ones above.
In practice, any one of these factors could limit the
Glucose
The glucose produced in
photosynthesis may be used in various
ways by plants and algae.
Use
Some glucose is used for
respiration to release
energy. Some is used to
produce:
•Cellulose - which
strengthens the cell wall
•Proteins - such as
enzymes and chlorophyll
Storage
Glucose is needed by cells for
respiration. However, it is not produced
at night when it is too dark for
photosynthesis to happen. Plants and
algae store glucose as insoluble
products. These include:
•Starch
•Fats and oils
Plant nutrients
Plants need nutrients to stay healthy and
grow. The most common type of
fertilisers used contain NPK
N- nitrogen
P- phosphorous
K- potassium
fertilisers contain minerals such as:
• nitrates which are needed to make proteins.
Proteins are needed for cell growth
• phosphates for respiration and growth
• potassium compounds for respiration and
Photosynthesis
• magnesium compounds for photosynthesis.
mineral deficiencies to the resulting poor
plant growth:
• nitrate – poor growth and yellow leaves
• phosphate – poor root growth and
discoloured
leaves
• potassium – poor flower and fruit growth
and discoloured leaves
• magnesium – yellow leaves.
Nitrogen is needed for plant growth as it
is used to make proteins, too little
nitrogen and the plant will have stunned
growth, too much then the plant will
grow too quickly, become long and
spindly and then will be prone to wind
damage.
Phosphate is needed for respiration and
growth of the plant, without it plants
will have yellow leaves and the roots will
grow slowly
Potassium is needed for respiration and
photosynthesis ( its is used to make the
enzymes used in these processes),
without it the leaves will turn
yellow/brown at the edges and the plant
will have less flowers and fruit
Magnesium makes the compounds needed
for photosynthesis, without it the plant
will have yellow leaves and less crops will
be produced
Nutrients get into the plant through the
roots, they dissolve in water to make
soil solution, the nutrients travel
through the plant in the xylem
Fertilisers-substance added to the soil to
improve plant growth
Organic fertiliser- a natural substance
such as manure, bone meal and wood ash
Inorganic fertiliser-chemicals made with
the right balance of each nutrient
Organic fertilisers
Inorganic fertilisers
Signs of a unhealthy plant.
Wilting- the cells are flaccid
Slug snails and fungi on the plants
• Explain why plant nutrients are important
and the problems the plant may have if
they do not have enough nutrients
What factors affect plant
growth?
LO- to explain the factors which affect
plant growth
Economics Of Greenhouse
Farmers can use their knowledge of factors limiting the rate of
photosynthesis to increase crop yields.
This is particularly true in greenhouses, where the conditions are
more easily controlled than in the open air outside:
•The use of artificial light allows photosynthesis to continue beyond
daylight hours. Bright lights also provide a higher-than-normal light
intensity.
•The use of artificial heating allows photosynthesis to continue at an
increased rate.
•The use of additional carbon dioxide released into the atmosphere
inside the greenhouse also allows photosynthesis to continue at an
Paraffin
lamps
increased
rate. have traditionally been used in greenhouses. Their
use increases the rate of photosynthesis because as well as the
light generated from the lamps, the burning paraffin produces heat
and carbon dioxide too.
Pollination is the transfer of pollen from
the anther to the sigma, this is needed
for fertilisation.
There are two main ways for pollen to be
transferred; by insects and by the wind
Insect or wind pollination?
Cross pollination is the transfer of pollen from
one plant to another. This is done to increase
the gene pool.
To stop self- pollination some plants are
dioecious which means that male and female
parts are on different flowers.
Anthers and stigma may mature at different
times on some plants.
A seed contains everything a plant needs
to grow. It contains enough food for the
plant till it gets to a stage where the
plant can photosynthesise
The testa protects the seed from attacks by
insects
The micropyle is a small hole inside the testa
which allows water into the seed, this will
cause is to swell and split the testa- ready for
germination
The cotyledons form the first two leaves of the
plant
The pulmule forms the roots when a plant
germinates, and the radicle forms the shoots
• To germinate, plants need water, oxygen
and the correct temperature. oxygen is
needed for respiration to provide the
energy needed for growth
• Seeds are said to be dormant before
they germinate
Look at this list of characteristics of strawberry plants.
Strawberries rot quickly
Plants will not die in
temperatures below 4ºC
strawberries stay fresh for a
week after picking
Big strawberries
Plants produce lots
of strawberries
strawberries are bright red
Plants are resistant to disease
strawberries are very tasty
strawberries are juicy
Small strawberries
Plants can survive with little water.
Plants have small leaves
Which characteristics are important to: a) A farmer, b) A shopper?
If you were a plant breeder, which 5 characteristics would you like
your new variety of strawberries to have? Explain your choices.
• What is selective breeding and genetically
modified food?
• LO- to explain the advantages and
disadvantages of selective breeding and
GM food
Selective breeding is the
process where plants or animals
are breed for a chosen
characteristic
they can be selectively bred to
improve yield, resistance to
disease and climate, taste and
appearance
http://www.youtube.com/watch?v=mtVtpO7FOaA
When two different species are crossed a
hybrid is produced
Hybrid vigour is when characteristic in
the offspring have improved from the
characteristic in from the parents
• Genetic engineering allows use to put a
gene from one organism into another
organism to give it new characteristics
• For example a gene from a fish which
can live in cold seas can be put into
tomato plants to allow it to survive in
cold climates. GE could also be used to
kill weeds
• People worry as they we do not know the
consequences of eating genetically modified
food and we do not know what it will do to the
environment
• Will these genes be transferred to weeds?
What will happen to the biodiversity?
http://www.youtube.com/watch?v=0WSCs78Gl9M
Task- create a farm which is pro selective breeding and
genetically modified food:
what characteristics have the plant been selected for?
What are the advantages and disadvantages of
selectively breeding of plants?
How could you use selective breeding to increase crop
yields?
How could you improve crop by genetic engineering?
Inside the nucleus of a cell we find our
DNA. A gene is a section of DNA which
codes for a trait (eg hair colour, eye
colour). Genes are grouped together in
chromosomes.
The genetic make up of an organism is
called its genotypes. There are two
genes for each characteristic/trait.
The organisms phenotype is the
characteristics/trait we see.
Different copies of the same gene are
called alleles. Alleles may be dominant
or recessive. Dominant alleles are always
expressed over recessive alleles.
http://www.youtube.com/watch?v=ubq4eu_T
DFc
Monohybrid inheritance
• http://www.youtube.com/results?search_query=dominant+genes
When the F1 generation was crossed with F1
generation (e.g. round seed(F1) & round seed(F1)
crossed), both round and wrinkled seeds were
produced. This tell us about that traits are
determined by two different allelles, one dominant
and one recessive.
We cultivate soil to make it ready to grow
crops. We remove weeds and improve
the soil structure.
In autumn we fork the soil to loosen it up.
This allows air in and allows the soil to
break down due to frost. We out
trenches into clay soil to increase the
surface area which allows weathering to
break up the soil and the soil to aerate
as water can drain out more easily.
Single Digging
• aerates the soil
• removes weeds
• improves drainage
• FYM can be added to improve
crumb structure
• raked to produce a good tilth
Soil crumbs are formed from inorganic
soil particles sand, silt and clay, are held
together by humus.
A good soil crumb is important to allow
the soil to be aerated, retain moisture
and nutrients and allow the water to
drain. If the soil is too dense the roots
will find it difficult to grow and the soil
will become water logged, if it is too
sandy it will drain too easily washing
away the nutrients and the structure
will not support the plants.
• We can improve the soil fertility by
adding humus, compost or well rotted
manure to the soil, they are all rich in
nutrients especially nitrates. They will
release nutrients over a period of time.
Clay
Water
Humus
Sand
Silt
Lime can be added to clay soil, it causes
the soil to flocculate which means it
sticks together to allow the soil to
aerate and drain. It is also an alkali so
can neutralise acidic soil.
Sand can be added if you need to drain
clay soil very quickly but can make it
heavier.
Storing Crops
Ripening
Bruising
Pests
Diseases
• A problem with storing food is their
perishability- the likely hood they will spoil or
decay. This is caused by the growth of fungi,
moulds and bacteria on the crop.
• Pest and disease are another problem, rats
and mice will invade barns which contain
stores of food. Animal pests will bring
disease.
Managing pests
• Lowering the temperature of stored food will
stop pest being able to survive which will
prolong the life of the food. Respiration is
reduced at lower temperatures.
• The atmosphere can be controlled so there is
not enough oxygen for organisms to survive
• Fruit is normally picked before it is ripen and
the gas ethylene is used to ripen the fruit