1. 8 P.S. Seed & Plant breeding etc 1

2. Seed Germination, Plant Breeding,
Microorganisms and the Plant
Kingdom, Plant Classification
Tutor = Dónal Chambers

3. Learning Outcomes
 (4) Outline the life cycle and development of plants in respect of
seed structure and germination including dormancy, the
vegetative plant and vegetative propagation, the flowering plant
and sexual reproduction and the fruiting plant and fruit
classification
 (7) Outline the processes involved in conventional plant
breeding including the production of first filial generation of
hybrid seed.
 (8) Outline the main characteristics of micro-organisms to
include fungi, bacteria and viruses and their role in the plant
kingdom.
 (9) Investigate the system of plant classification including
principles of classification, divisions of the plant kingdom, the
binominal system of nomenclature and the naming of hybrids3

4. Sexual Reproduction (SP)
 SP = Reproduction involving a Male and female
gamete which unite to form a zygote
 This process is called fertilisation
 How = pollination is needed first
 Pollination = is the transfer of the pollen from the
anther to the stigma
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8 P.S. Seed & Plant breeding etc

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•When the pollen
lands it forms a tube
down into the ovary to
get to the egg
•It carries two sperm
nuclei down
•One fertilises the
egg (ovule)
•The other sperm
nuclei joins two ‘polar
nuclei’ to form the
endosperm

8. Seed Formation
 The fertilised ovule becomes the seed
 The zygote divides by many times forming the root
(radicle) and a shoot (plumule) of the embryo
 The Endosperm nucleus divides, grows and stores food
for the embryo (mainly oils and starch)
 Certain cells become the cotyledon (seed leaf)
 The cotyledon will absorb nutrients from the
endosperm as the seed grows

9. Seed - Structure
9
2 Plant S. - Extern. Anatomy
Micropyle

10. Fruit Formation
 Auxin stimulates the surrounding ovary to become the
fruit (swollen with food)
 Fruit Function = protect the seed & help with seed
dispersal
Types
 Some are fleshy (peach) others are dry (pea pods)
 False fruits (apple) = the fleshly part is not from the
ovary but is from swollen flower parts at the base

11. 8 P.S. Seed & Plant breeding etc 11

12. Types - Fleshy Fruit are formed from
A single flower:
 Berry = single fleshy fruit without a stone, may contain a
single seed or several seeds, tomato, passion fruit
 Drupe = single fleshy fruit with a hard stone at center =
peach, cherry, apricot
 Aggregation of drupes = made up of many drupes each
formed from a single flower = raspberry, loganberry
 Pome = fleshy fruit which didn't form from the ovary wall,
apple, pear
 Hesperidium = berries that have a tough aromatic rind,
oranges, lemons
A group of flowers = Aggregate fruits are pineapple and
fig

13. Dry Dehiscent fruits- split open
 Legume = several seeds enclosed in a seed capsule which
splits along 2 sides = peas, beans
 Capsule = dry fruit which splits open to release seeds,
classified according to how it splits, poppy
 Follicle = splits on one side only = delphinium
K

14. Dry indehiscent fruit – don’t split open
 Achene = single seeded fruit with a thin outer wall which
developed from the ovary wall = dandelion, sunflowers
 Grain = single seeded and ovary wall and seed are fused
together = grasses
 Nut = similar to achenes, larger in size = walnuts, oak,
chestnut, hazelnut
K

15. Dormancy – embryo rests for while
 A resting period when the seed undergoes no growth
and has reduced metabolism
Why?
 It allows time for the seed to be spread a distance from
the parent plant before it germinates i.e. By wind or by
animal
 To allow favourable ecological conditions to come
about i.e. Spring to arrive with suitable temperatures

16. Dormancy – How to prevent germination
 How
 Growth inhibitors (abscisic acid)
 Testa impermeable to water for a time
 Testa to tough for a time
 Lack of growth promoters for a period of time
 In horticulture these can be changed to end dormancy
or in the wild the cold winter will change them and
allow germination to take place

17. Germination
 This is when the seed develops into a plant
 It is the re-starting of growth of the embryo after a period
of dormancy under suitable environmental condition
 Suitable conditions include
 Temperature
 Water
 Oxygen
 Light (stimulates germination in only certain seeds i.e.
lettuce
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8 P.S. Seed & Plant breeding etc

18. Germination factors
 Temperature = The requirements are specific to a particular
plant. The correct temperature allows chemical reactions to
occur in the plant. Generally 10-20°C is required
 Water = The water content of a seed can fall to as low as 10%
and needs to be restored to 70% to enable germination to occur.
Water is taken in through the testa (seed coat) and allows
chemical activity to occur.
 Oxygen = Essential for aerobic respiration
 Light = Some species are inhibited by the presence of light,
Rhododenderon and other require it (or are stimulated by it)
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8 P.S. Seed & Plant breeding etc

20. Vegetative propagation
 Still on LO 4 here
 This includes layering, division and cuttings which is
covered in the plant propagation module
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8 P.S. Seed & Plant breeding etc

21. LO7 = Plant Breeding
 Outline the processes involved in conventional plant breeding
including the production of first filial generation of hybrid seed.
 We use Mendel’s work as the basis
for modern plant breeding particularly
the production of F1 hybrids
 It is the first filial (F1) generation of
offspring (seed) from two very distinct parents
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8 P.S. Seed & Plant breeding etc

22. F1 Hybrids
 Produced for the commercial market to provide uniformity
How = Inbreeding
 Firstly parent plants with the necessary dominant
characteristics are required (i.e. resistance to a disease)
 These are developed by self pollinating and selecting plants
over 8-12 generations to produce inbred parent lines
 The pure bred parents are then cross pollinated and the
resulting generation is called F1 hybrid
 it displays uniformity and vigour

23. Benefits of F1 hybrids
 Hybrid Vigour, after successive generations of inbreeding,
F1 varieties display outstanding growth in good growing
conditions.
 Uniformity,
 All can be harvested at the same time
 Same size and colour
 Desirable characteristics like flower colour, vegetable size
etc displayed.
 All plants genetically identical

24. Disadvantages of F1 hybrids
 Seed saved from F1 varieties produces variable offspring
(or sterile offspring)
 Money = Seed is expensive
 Time = takes a number of years to develop
 Susceptible = All plants are genetically identical and
therefore a monoculture and susceptible to all the same
pests and diseases
 Glut = All plants mature at the same time which may not be
suitable for a domestic vegetable garden situation

25. Genetic engineering
 It involves the the addition of new DNA to an organism
using technology (it can be from a different species)
 The objective is to introduce new traits/characteristics
not already found in that organism.
 It is commonly used in plants to introduce disease
resistance or tolerance to pesticides or herbicides.
 Soybean, maize, rapeseed and cotton are some of the
most widely grown genetically modified crops.

27. Gene banks
 With all of the advances in plant breeding and the production of
new cultivars, older varieties are being lost and these could be
valuable in the future. (genetic diversity)
 A gene bank provides a means of conserving and storing large
amounts of seeds at low temperatures, plant material may be
stored using tissue culture.
 Seed savers plays an important role in Ireland wtih older
varieties and its important that these are conserved for the
future.
 http://www.irishseedsavers.ie/

28. Fungi, Bacteria and Viruses and
their role in the plant kingdom
 Fungi & Plants
1)Parasitic = some fungi are parasitic on plants stealing nutrients
from them. (Covered in Plant Protection)
2)Mutually beneficial
 ‘Mycorrhiza’ where fungi live on and in the plant’s roots.
 Approx = 90% of plants have these relationships
 The fungus receives sugars from the plant and the
fungus allow the plant to increase its water and
nutrient uptake from soil

29. Fungi & plants
3) Decomposition
 Fungi are essential in breaking down plants after they die
 This is a critical step in soil health with the addition of
organic matter to soil
 This leads to the creation of humus in the soil
 Nutrient recycling = It allows bacteria in to convert the
nutrients into available forms in the soil

30. Bacteria & plants
1. Disease causing = Some cause diseases such as canker
and were discussed in plant protection
2. Nitrogen fixing = Rhizobium bacteria in the root nodules
of legume plants covert atmospheric nitrogen to NH3
3. Decomposition = break down dead plants = recycling
nutrients
4. Induced Systemic Resistance = beneficial bacteria in the
roots create a reaction in the plant which activates
defense mechanism against harmful bacteria.

31. Viruses & plants
1. Disease causing = i.e. tobacco or cucumber mosaic virus
2. Most are non disease causing to plants as they are very
specific to certain hosts and work by affecting the genes
of plants.
 NB point is to control the vector of the virus such as
aphids rather than the virus itself or use clean equipment
etc and resistant varieties.

32. (9) Investigate the system of plant classification
including principles of classification, divisions of
the plant kingdom, the binominal system of
nomenclature and the naming of hybrids
 Covered in the Plant Identification with Graham
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8 P.S. Seed & Plant breeding etc

33. Hybrid plants
 Many hybrids are created by humans, but natural hybrids occur as
well. Plant species hybridize more readily than animal species, and the
resulting hybrids are more often fertile hybrids and may reproduce,
though there still exist sterile hybrids and selective hybrid elimination
where the offspring are less able to survive and are thus eliminated
before they can reproduce. A number of plant species are the result
of hybridization and polyploidy with many plant species easily cross
pollinating and producing viable seeds, the distinction between each
species is often maintained by geographical isolation or differences in
the flowering period.
 Since plants hybridize frequently without much work, they are often
created by humans in order to produce improved plants. These
improvements can include the production of more or improved seeds,
fruits or other plant parts for consumption, or to make a plant more
winter or heat hardy or improve its growth and/or appearance for use
in horticulture. Much work is now being done with hybrids to produce
more disease resistant plants for both agricultural and horticultural
crops. In many groups of plants hybridization has been used to
produce larger and more showy flowers and new flower colors.
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