PLANTS

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					Growing Plants from Seeds


All seeds contain an embryo plant with a
root and shoot.
The seed also contains a starchy food store
which the embryo uses as energy to grow. (
germinate )
The seed coat protects the embryo from
damage by micro-organisms that live in the
soil.
             Germination
• Germination is the growth of a plant
  embryo into a plant with green leaves.
• The embryo uses the food store for
  energy.
• A seed needs three things to grow
  – Warmth
  – Water
  – oxygen
Test Tube         Number of
                  seeds growing
1 (warmth ,air,   10
water)
2 ( no water)     0
3 ( no air )      0
4 (no light )     9
5 ( cold )        2
Photosynthesis
Plants make food by a process called
photosynthesis.
All green parts of the plant make food but
most food is made in the leaves.
Plants need light to make the food starch.
This food is then used by plants for
growth.
Testing leaves for Starch
When leaves are tested for starch, they
need to be boiled first
to open the cells.
Alcohol is used to remove the green colour.
Finally, iodine is added.
Iodine turns blue/black when starch is
present.
              Testing for Photosynthesis
• Glucose manufactured in the process of photosynthesis can be stored as
   starched. We can test for starch using iodine solution following the steps
   outlined below.
Sowing Seeds
When planting seeds, the way they are
planted depends on the seed size.
Fine seeds should be mixed with silver sand
to space the seeds out. This stops them
fighting with each other for water, root
space and light.
Medium size seeds can be scattered over
the surface of the compost ( soil ).
Large seeds can be sown individually in seed
trays or pots.
           Pelleted seeds
• A pelleted seed is coated in layers of
  material such as clay before it is planted.
• This can make irregularly shaped seeds
  round and smooth to stop them sticking
  together.
• Useful chemicals such as fungicides,
  pesticides or nutrients can be added to the
  layers.
• Pelleting makes small seeds easier to
  handle.
Dormancy
Many seed will not germinate after they are
dispersed,
Even although they have been given ideal
conditions.
These seeds are dormant and need a long
cold period before they grow.
This stops them growing during a warm
winter spell.
               Chitting
• Pre-germinating or chitting a seed
  means making it start to germinate
  before it has been planted.
• This can be done by soaking the seeds
  in water for a few days.
• If the seed coat is very tough and will
  not allow water to enter, it can be slit
  open using a sharp knife.
• This is best done at the opposite side
  from the embryo to avoid damage.
• If the seed is very big, a nail file can
  be used instead to file away part of
  the seed coat.
• Very small seeds can be rolled in
  between sheets of sand paper.
    Vegetative propagation
• Propagation is a way a grower can increase
  their supply of plants.
• Vegetative propagation is a way of growing
  plants without using seeds.
• This involves structures such as bulbs and
  cuttings and all new plants formed are
  identical to the original parent plant.
• Vegetative propagation produces new
  plants faster than using seeds.
     Natural vegetative propagation
• Bulbs
  – A bulb is a natural plant
    propagation structure. It
    is made up of several leaf
    bases (layers) which
    contain stored food
    (starch) and has a short,
    thick stem.
  – Buds can be found among
    the leaf bases and grow
    into new daughter bulbs.
  – Tulips and daffodils grow
    from bulbs.
• Tubers
  – A tuber is a large food store
    found on a root or stem.
  – A potato is an example of a
    tuber.
  – Tubers can grow into whole
    new plants
  – In summer, potato plants
    grow many tubers and each
    tuber has ‘eyes’ which are
    really tiny buds. When
    planted, shoots grow from
    the bud and turn into new
    potato plants.
• Plantlets
• A plantlet is a tiny plant
  attached to a parent plant.
  These plantlets eventually
  separate from the parent
  and grow on their own.
• The Mexican hat plant
  grows plantlets on the
  edges of its leaves.
• The Piggyback plant grows
  plantlets at the base of
  each leaf.
Mexican hat plant
Piggyback plant
• Runners
  – Some plants grow
    plantlets at the end of
    horizontal stems called
    runners.
  – Spider plants grow
    runners.
  – Strawberries grow
    plantlets on runners.
  – If runners are pegged to
    the ground, the plantlets
    grow roots and the
    runner can then be cut.
• Offsets
  – An offset is a plantlet
    which grows as a side
    shoot at the base of
    the parent plant..
  – Sometimes lots of
    offsets grow and form
    a clump.
  – Mother-in-law’s tongue
    is a plant which grows
    offsets.
Plant production
Artificial Propagation
Artificial propagation is when part of a
plant is cut from the parent and used to
make a new plant.
This is quicker then waiting for the
parent plant to make seeds and all the
new plants will be identical to the
parent.
A cutting is a piece of plant stem with
leaves which is cut, dipped in rooting
hormone ( encourages roots to be made )
and planted .
Layering is another method of artificial
propagation.
A long stem is nicked, dusted with rooting
hormone and pegged to a pot of compost.
When the roots grow, the new plant can
be cut from the parent.
This makes bigger new plants and the
parent supplies it with water and minerals
while they are attached.
             Using heat during
                propagation
• A propagator is an electric device for
  providing cuttings and new plants
  with heat. Propagators are often
  used inside greenhouses.
• Propagators keep the soil at a
  siutable temperature 24 hors a day.
• This encourages roots to grow
  quickly.
• Propagators are mot useful during
  winter to protect young plants from
  frost damage.
• Gardeners must be careful not to
  make the temperature too high for
  young plants as they will lose too
  much water and wilt.
• Some propagators have thermostats
  which control the temperature. This
  allows the temperature to be set by
  the gardener and it will stay constant.
Composts
For plants to be healthy, the soil ( loam) must be
  right for the plant.
The soil must have :
1. Air
2. Good drainage
3. Minerals
4. Free of most bacteria or fungus
There are 2 kinds of compost : loam based and
loamless
Loam based soils contain mainly loam.
Loamless soils contain a 1:1 ratio of peat to sand
Loamless soils do not need to be sterilised but can
dry out more easily.
• Rooting Composts: Sometimes called a
 cutting compost,this is a mixture of peat
 and sand in a 1:1 ratio (half and half). Water
 drains better from this compost because it
 has more sand and this prevents roots from
 rotting. Perlite or vermiculite can be used
 instead of sand.
• Potting Composts: This is a mixture of peat
  and sand in a 3:1 ratio so for example, 6L of
  peat would be mixed with 2L of sand.
  Fertiliser is also added to supply the
  growing plant with enough minerals to keep
  it healthy.
Materials         Property

Sand or perlite

Peat

Fertiliser

Loam (soil)
Fertilisers
Plants need minerals for healthy growth.
The 3 main minerals :
1. Nitrogen : leaf growth
2. Phosphorous : root growth
3. Potassium : flower and fruit growth
Plants also need some other minerals in tiny
   amounts. These are called trace elements and
   an example is iron.
Fertiliser is used if a soil does not have enough of the
right minerals.
Different plants need varying amounts of each of the
3 main minerals.
For example grass needs nitrogen as the main
element of fertiliser whereas, growing tomatoes
would need high potassium ( potash).
The proportion or ratio of the 3 main minerals is
listed on fertiliser containers in the following order
Nitrogen (N) : phosphorous (P) : potassum (K)
    7        :        7         :      14
Applying Fertilisers
Fertilisers come in 2 forms , as liquids or granules (
small pellets)
Liquid fertilisers are quick acting but drain away
from soil quickly
Granules release minerals slowly and are longer
lasting.
Some liquid fertilisers can be absorbed by the
leaves as well as the roots ex Miracle Grow .
Man made or natural fertilisers (organic) can be
used. An example of an organic fertiliser would be
manure but they can be bought from shops also.
       Watering house plants
• Some plants should be watered from above.
  A watering can can be used to pour water
  into the plant pot. Water is added until a
  small amount appears in the drainage saucer
  underneath.
• Some plants should be watered from below.
  The pot or tray should be placed in shallow
  water for about 15 mins to allow the roots to
  absorb as much water as they need. African
  violets and young seedlings should be
  watered in this way
Watering Systems
Automatic watering systems allow plants to be
  watered without anyone having to do the job.
What are the advantages of this ?
There are several different types :
1. Trickle irrigation
Plastic hose connects a tank of water with several
   pots. Water “trickles “ continuously between
   the pots.
2. Capillary Bench
Capillary matting is a material that will suck up water and
stay moist. If one end of the water is placed in a water
trough , it will absorb water along its length , and plant pots
can be placed on top.
3. Water Retentive Gels
These are chemicals that can absorb and hold a great deal
of water. If mixed with soil , they can last many seasons
holding water for plants. This is useful for hard to reach
plants ex. Hanging baskets
Temperature
Temperature is measured in degrees
Centigrade (ºC )
Different types of plants grow best at
different temperatures. For example a
spider plant grows well between 10 and
30°C. At temperatures outside this range
the plant does not grow well and may die.
People who grow plants must find ways of
growing them at the correct temperature.
Greenhouses are often used or polythene
tunnels which are plastic sheets draped over
metal poles, almost like a tent for plants!
• The temperature inside greenhouses
  or polythene tunnels can be controlled
  using an electric heater.
• The grower sets the thermostat at a
  certain temperature and when the
  greenhouse is warm enough the
  thermostat switches the heater off.
• When the greenhouse begins to cool
  down the thermostat switches the
  heater back on.
Growers can check the range of temperatures
their plants have been exposed to in the
previous 24hours using a maximum and
minimum thermometer.
This is u-shaped. One arm records the
maximum temperature that occurred in the
previous 24 hours and the other arm records
the minimum temperature that occurred in the
previous 24hours.
As liquid in the thermometer moves up or
down it pushes metal markers. These show
the max and min temperatures.
• Both arms also show the present
 temperature. The position of the
 liquid inside the thermometer
 shows this.
Humidity
This is the amount of water vapour in
the air.
Plants lose water from their leaf
surfaces. This has a cooling effect
similar to sweating in humans.
If the air is very humid, hardly any
water will evapourate from the plant. If
the air is very dry, the plant may lose
too much water and could die.
Different levels of humidity suit
different types of plants.
Relative humidity is the percentage of
 water vapour the air is holding.
 The higher the percentage, the more
 humid the air.
100% humidity means the air can hold no
  more water vapour and is saturated
• A wet and dry hygrometer is used to
  measure relative humidity
• It is made up of two ordinary
  thermometers but one bulb is
  wrapped in wet muslin and will show a
  lower temp.
• Relative humidity is worked out as
  follows:
  – Read dry bulb temp
  – Read wet bulb temp
  – Subtract wet reading from dry reading.
    Refer to table of relative humidities and
    find value
Ventilation
This is providing fresh air. Stale moist air means
mould and mildew will grow and kill plants.
Automatic vent openers are cylinders full of wax.
The wax expands when the temperature gets too
high and this pushes the window open. As the
green house cools down the wax contracts and the
window closes.
Extractor fans can also be used to cool green
houses. These are switched on and off by
thermostats.
Potting On
If a plant grows too large for the pot it is in,it will
not have enough space for the roots to grow. We
say it has become pot-bound. You will recognise
such a plant by the following features:
~ slow growth rate
~ compost dries quickly
~ roots growing out holes in bottom of pot
Potting on means re-potting the plant in a larger
pot.
Pricking Out


When seeds are planted in a seed tray, they
eventually start to fight for light and root space.
They are now ready to transplant into pots and this
process is called pricking out . This means
transferring them to a new location where they will
have more room to grow.
Seedlings are ready to prick out when their first set
of leaves open out.
               Dead Heading
• Normally a plant produces a set of flowers which
  die after making seeds. If the heads of dead
  flowers are removed regularly the plant may
  produce more flowers.
• This removal of dead flower heads to encourage
  the plant to continue flowering is called dead
  heading.
• Dead heading allows the plant to direct energy to
  dormant flower buds instead of fruit production.
Types of Plants
House plants can be divided into 4 groups :
Flowering Plants : we grow these for their
attractive flowers. Some varieties flower year
after year (geranium) and some only once.
Foliage Plants : we grow these for the shape
and colour of their leaves.
Succulent Plants : these have fleshy leaves or
stems that store water eg. Cacti. Some may have
sharp spines and sometimes produce flowers.
Native to dry enviroments such as desert or
jungle.
• Ferns: Non-flowering plants native to
 damp woodlands that are not brightly
 lit. Will not survive in dry, hot
 conditions.
           Pests and disease
• A pest is an animal which causes damage to
  a plant. An example in an aphid (greenfly).
  Greenfly suck the plants sugary sap using
  their sharp, syringe-like mouthparts.
• The greenfly usually attack young parts of
  the plant like the flower buds. The plant
  cannot grow properly because it is not
  getting a full supply of energy
• Disease is caused by a micro-organism that
  can damage the plant. An example is grey
  mould which is a fungus.
• This disease causes a fuzzy grey fungal
  growth on the leaves . Infected leaves
  quickly rot and die and infection can spread
  to the rest of the plant.
• This disease thrives in damp, poorly
  ventilated conditions.
           Control of Aphids
• A pesticide is a chemical that kills insects
  and other pests. An insecticide is a type of
  pesticide especially for insects.
• Plants can be sprayed with insecticide and
  so any aphid which tries to feed on its sap
  will die.
• Aphids can also be controlled by biological
  methods. This means introducing one of its
  natural predators (ladybirds) which will eat
  them before they can destroy the plants.
       Control of grey mould
• We can prevent this disease by making sure
  plants are well spaced out and given good
  ventilation. Any infected plants should be
  removed and burned immediately to prevent
  spread of the disease to other plants.
• Plants can also be sprayed with a chemical
  called a fungicide which kills fungi such as
  grey mould.
         Protected cultivation
• Plants can be damaged by wind, rain, low
  temperatures and in particular, frost.
• We can protect plants from damage by
  protective cultivation. This also allows
  farmers to plant seeds earlier and therefore
  sell their crops early and receive a higher
  price.
         Methods of protection
• Glass (ex.greenhouse or cloche)
  –   Lets light through
  –   Permanent
  –   Retains heat
  –   Not damaged by wind
• Plastic (cloche)
  – Light and easy so handle
  – Less easily broken than glass
  – cheap
• Polytunnels
  – Good for large areas
  – Made of transparent plastic stretched over wire
    hoops like a tent.
  – Can be raised at either end for ventilation
• Floating fleece
  – Sheet of woven man-made fibres
  – Place over crops and is gradually lifted up by
    plants as they grow.
  – Helps keep soil warm and protects against pests
  – Water and air can still get through

				
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