Download Sexually Transmitted Diseases

REPRODUCTION IN
PLANTS:
THE SIGNIFICANCE
OF SEEDS
ABBOTTS
TOPICS
Use of seed banks to maintain biodiversity
Importance of seeds as a source of food
Endemic species in South Africa
• The ovary (with ovules) grows and develops into fruit
• The stigma and style dry and fall off.
• The fruit protects the seed.
3
SEED DISTRIBUTION
4
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Fruit fall down, burst open and seeds
are released.
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Seeds are distributed by:
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Wind
Insects/other animals
Water
Humans
Seeds are adapted according to the
method in which they are dispersed,
e.g. wings and hooks.
EXTRA STUFF
EXTRA STUFF
SEED BANKS
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Many plant species are
currently under threat
By saving seeds, many
of these plants could be
saved
A seed bank is a facility
used to store seeds of
various plants in an
effort to maintain
biodiversity
Many countries have
seed banks
Kew millenium seed bank at Wakehurst
Place, Sussex.
Seed collections arrive by courier from
around the world
The largest seed in the collection is the
coco de mer seed and the smallest is a
Chilean orchid – there are about 1m seeds
in the vial
The seeds, together with pressed plant
specimens and vital field data, are brought
back to seed banks around the world for
processing, research and long-term
storage
Cleaning acer seeds. Once at the seed
bank, seed is cleaned to reduce bulk and
the risk of disease. This requires great care
and expertise and to limit damage, much of
the work is done by hand using sieves
Seeds in temperature cabinet, testing for viability.
Most species have seeds that stay viable when dried
to the low moisture levels necessary for long-term
storage. However, certain species have seeds that
are not tolerant to drying and cannot be conserved
long-term in a seed bank. There are other ways to
deal with these species
Once the seed has been dried to the
required level it is packaged and placed in
the cold room where it is kept at a
temperature of -20C
The length of time that each collection can
be stored for is fixed by the biology of the
seed. Depending on the species, seeds
may live centuries – and even millennia
Eucalyptus virginii seed. The next phase of
the seed bank project is an even more
ambitious target of collecting a total of 25%
- about 75,000 - of the world's plant
species by 2020
which is established in the permafrost in
the mountains of Svalbard, is designed to
store duplicates of seeds from seed
collections around the globe. Many of
these collections are in developing
countries.
Built into a reinforced concrete tunnel
Drilled 70m into the mountain
Aims to store 4.5 million seed samples from
Every country in the world
Store seeds at -180C
Will be viable for thousands of years
VALUE OF SEED BANKS
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Seeds can be grown to replace seeds that are lost
as a result of
Over-exploitation of wild plants
 Invasion of alien plant species
 Habitat loss (development of cities etc)
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Seeds can be grown to maintain/restore
biodiversity
Seeds can be used for research in bioengineering (try and find solutions to crop
failures)
Seeds can be grown to produce plants for
pharmaceutical research
SEEDS AS A FOOD SOURCE
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Seeds contain stored food (starch, protein, oil)
for feeding the new plant until it can support
itself
Seeds are a good source of food for humans
Roots, stems, leaves, flowers and fruits are
also food sources for humans!
PLANTS WITH EDIBLE SEEDS
Grains
(cereals)
• Have a high starch content
• Maize, wheat, rice, oats
Pulses
• Have a high protein content
• Pea and bean plants
Nuts
• Have a high oil content
• Any large, dry oily seed found
within a hard shell
IMPORTANCE OF GRAINS
AND PULSES
20
Form the staple diet of
most of the world’s
population
•Eg maize, wheat, rice oats
Have a high
nutritional value
Are cheap
•Principle nutrient is
carbohydrate, but they
are also a valuable
source of protein,
especially in poorer
countries
Wheat
Maize
Rice
Oats
GRAINS/CEREALS
VALUE OF GRAINS
eg maize, wheat, rice, oats provide:
•A rich source of starch which is a good source of energy
•Fibre from the seed coat of whole grains helps to keep the
bowel healthy
•Most of the B vitamins and many minerals from the seed coat
•Small amounts of protein and fat
PULSES
peas
beans
Peanuts
Soya Beans
VALUE OF PULSES
Eg lentils, peas, beans, peanuts and soya beans
•Are a good source of protein, minerals and B Vitamins
•Help regulate blood sugar levels
NUTS
Pecan
Almond
Cashew's
VALUE OF NUTS
Eg almonds, pecans, cashews
•Are a good source of energy
•Are rich in monounsaturated or polyunsturated fatty
acids (healthier than animal fat)
•Supply Vitamin E
OIL SEEDS
peanuts,
soybeans
sunflower
corn,
canola
VALUE OF OIL SEEDS
Eg peanuts, soybeans, corn, sunflower and canola
•Are rich in monounsaturated or polyunsaturated
fatty acids
•Can contain vital omega-3 fatty acids
TO DO
TEXTBOOK PAGE 65
IMPORTANCE OF SEEDS AS FOOD
LEARNING ACTIVITY 20
ENDEMIC SPECIES IN SOUTH AFRICA
PAGE 66
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An endemic plant is one that grows only in one
specific geographic area or habitat type
Of the 20 000 plant species in South Africa, 66%
are endemic to various parts of the country
Endemic plants can easily become endangered if
their habitat changes
Changes are mainly due to the actions of humans
The seeds of these plants have great potential
Can be used for many purposes
FYNBOS VEGETATION
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Of the 9000 species in the fynbos vegetation
zone of south western South Africa 6 200 are
endemic
1 000 are endangered
Many of the endemic species are extinct
Endemic: Organisms that are native and can be found
ONLY in that location.
Indigenous: Organisms that are native but can be found
elsewhere.
In biogeography, a species is defined as
native (or indigenous) to a given region
or ecosystem if its presence in that region
is the result of only natural processes, with
no human intervention.
Every natural organism (as opposed to
a domesticated organism) has its own
natural range of distribution in which it is
regarded as native. Outside this native
range, a species may be introduced by
human activity; it is then referred to as
an introduced species within the regions
where it was anthropogenically introduced.
An indigenous species is not
necessarily endemic.
In biology and ecology, endemic
means exclusively native to the biota of a
specific place. An indigenous species may
occur in areas other than the one under
consideration.
WHAT ARE ENDEMIC SEEDS USED FOR?
Restoration of biodiversity
• Seeds are collected and stored in seed banks
Research into pharmaceuticals
• South African plants are being used to investigate the possibilities of developing
new medicines
Production of food crops
• Endemic food crops have their origin in South Africa eg Rooibos tea
Counteracting the effects of climate change
• Spekboom is able to absorb large quantities of carbon dioxide given off by industry
Economic ventures
• Market for exporting of flowers eg proteas
To maintain the supply of these plants it is important to
Have a good supply of seeds
THE END
SEED BANK