Growing Plants from Seeds

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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.
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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

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Test Tube Number of seeds growing
1 (warmth ,air, water) 10
2 ( no water) 0
3 ( no air ) 0
4 (no light ) 9
5 ( cold ) 2
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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.
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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.
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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.

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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.
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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.

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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.
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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.

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• 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.

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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.

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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.

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• 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.

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• 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.

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Mexican hat plant
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Piggyback plant
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• 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.

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• 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-laws tongue is a plant which grows
  offsets.

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Plant production
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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 .
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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.
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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.

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• 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.

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• Composts
• For plants to be healthy, the soil ( loam) must
  be right for the plant.
• The soil must have
• Air
• Good drainage
• Minerals
• Free of most bacteria or fungus

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There are 2 kinds of compost loam based and
loamless Loam based soils contain mainly
loam. Loamless soils contain a 11 ratio of peat
to sand Loamless soils do not need to be
sterilised but can dry out more easily.
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• Rooting Composts Sometimes called a cutting
  compost,this is a mixture of peat and sand in a
  11 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.

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• Potting Composts This is a mixture of peat and
  sand in a 31 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.

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Materials Property
Sand or perlite
Peat
Fertiliser
Loam (soil)
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• Fertilisers
• Plants need minerals for healthy growth.
• The 3 main minerals
• Nitrogen leaf growth
• Phosphorous root growth
• Potassium flower and fruit growth
• Plants also need some other minerals in tiny
  amounts. These are called trace elements and an
  example is iron.

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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
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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.
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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

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• 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
• Trickle irrigation
• Plastic hose connects a tank of water with
  several pots. Water trickles continuously
  between the pots.

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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
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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 30C. 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!
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• 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.

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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.
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• Both arms also show the present temperature. The
  position of the liquid inside the thermometer
  shows this.

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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.
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• 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

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• 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

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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.
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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.
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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.
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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.

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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.

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Foliage Plants we grow these for the shape and
colour of their leaves.
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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.
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• Ferns Non-flowering plants native to damp
  woodlands that are not brightly lit. Will not
  survive in dry, hot conditions.

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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

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• 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.

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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.

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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.

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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.

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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

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• 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