Seed Technology

Nature and Importance of
Seed Technology

Seeds have been and still are the most
important staple food of the world.
Rice, for instance is the main carbohydrate
source of two-thirds of the world’s population.
Likewise, legumes (e.g. mungbean, peanut
and soybean) are rich sources of proteins
essential to a balanced human diet.
Importance of Seeds

What is a seed?
A seed is a minute plant with nourishing and
protecting tissues (Edmond et al., 1978).
-is a mature ovule consisting of an embryonic
plant together with stored food, all surrounded
by a protective coat (Copeland, 1976).

A seed is an embryonic plant in a resting stage usually
– though not always – supplied with food reserves in
cotyledons (seed leaves), endosperm (tissue normally
derived from the triple fusion of two polar nuclei of the
ovule with the second sperm nucleus of the pollen
tube), or perisperm (tissue derived from nucellus); all
this usually contained within protective structures
consisting of the testa derived from the integuments of
the mother plant and possibly other structures formed
in a variety of ways (Roberts, 1972).

What is Seed Technology?
A body of knowledge which deals on
the production, handling and storage
of seeds.

Seeds are the easiest and fastest means of plant
multiplication.
Therefore, knowledge in producing, handling
and storing high quality seeds is necessary for
successful crop production.
What is the importance of Seed Technology
to crop production?

Seeds remain to be the most important form of
germplasm.
As such maintaining the viability of seeds under
storage ensures the availability of genetic material which
could be used for crop improvement.

What is the importance of Seed Technology
to crop science?
By studying the seed or germinating seedling, man has
gained knowledge about growth regulators, respiration,
cell division, morphogenesis, photosynthesis and other
metabolic processes.
This is possible since inside each seed is a living plant
capable of exhibiting almost all the processes found in
the mature plant.

What are the uses of seeds to man?
a. Food and animal feed such as cereals, legumes and
vegetables seeds (squash, watermelon etc.).
b. Spices and condiments such as blackpepper, achuete,
anise, etc.
c. Beverage such as coffee, cocoa and chocolate.
d. Edible oil from coconut, soybean, peanut and sunflower.
e. Fiber such as cotton.
f. Commercial materials such as button, soap, paints.

Grains
Grains, the seeds produced from a
number of cereal grasses, are among
the most important food crops in the
world.
Cooked or ground and processed into
flours, oils, and other substances, they
are an excellent source of energy for
both humans and livestock.
Beer and other alcoholic beverages are
made from fermented grains.

Wheat Grains
Wheat grains must be
ground into flour
before they can be
made into easily
digestible foods such
as pasta and bread.
Flour has played an
important role in the
diet of Western
civilization since
ancient times.

Coffee Beans
Mature coffee beans
are actually fruit that
when fully ripe take on
a deep crimson color.
After drying and
roasting, the beans
change to a brown or
black color and are
ready for grinding.

Cacao
The cacao tree produces a fruit
from which cocoa is derived.
Following harvest the fruit is
fermented to give the cocoa seed,
or bean, its distinctive flavor.
Cocoa, containing approximately
20 percent protein, 40 percent
carbohydrate, and 40 percent fat, is
high in nutritive value. Côte
d’Ivoire, Ghana, Nigeria, and Brazil
are leaders in cocoa production.

Soybeans
Soybeans, cultivated for
many centuries
throughout Asia, are a
leading crop in the
United States. Soybeans
are used primarily to
produce protein meal
and oil.

Cotton
Cotton is natural vegetable
fiber of great economic
importance as a raw material for
cloth.
Cotton's strength, absorbency,
and capacity to be washed and
dyed also make it adaptable to
a considerable variety of textile
products.

Coconut
The coconut palm, cultivated
throughout the tropics worldwide,
grows to a height of nearly 30 m
(100 ft). All parts of the coconut
palm can be used. Besides the
fruit itself, the terminal bud, called
the palm cabbage, and young
stems are edible and in some
areas are considered a delicacy.
The sap can be made into
beverages, while dried coconut
husk fibers and leaves can be
transformed into a variety of
household items.

Sunflower
Sunflower plants are cultivated for
their seeds. Refined sunflower-
seed oil is edible and considered
by many equal in quality to olive
oil. Cruder sunflower oil is used for
making soap and candles. The oil
cakes (solid residues after oil is
expressed) are used as cattle feed.
The raw seeds are used in poultry
mixes and are consumed by
humans as well.

Black Pepper
Native to India and long
considered the world’s most
important spice, the black
pepper has been used to flavor
foods for over 3000 years. The
black pepper plant produces a
single-seeded fruit called a
peppercorn, which if dried while
immature and green, produces
the spice, black pepper.

Cashew
Although cultivated in parts of
Asia and Africa, the cashew is
native to the western
hemisphere. Related to the
mango, pistachio, poison ivy,
and poison oak, the cashew has
a wide variety of nonfood
applications, including the use of
cashew oil in the manufacture of
varnishes and plastics.

Pili Nut
Pili nuts have a rich,
buttery flavor, often
said to be superior to
that of almonds. They
are slender, with a
length of
appproximately 2-1/2
inches and a diameter
of around 3/4”. Pili
nuts have a hard shell
which protects a single,
sweet kernel.

What is RA 7308?
An act to promote and develop the seed industry
in the Philippines and create the National Seed
Industry council and for other purposes.

a) conserve, preserve and develop the plant genetic
resources of the nation;
b) encourage and hasten the organization of all
sectors engaged in the industry, integrate all
their activities and provide assistance to them;
c) consider the seed industry as a preferred area
of investment;
What are the responsibilities of the government under RA
7083?

d) encourage the private sector to engage in seed
research and development and in mass
production and distribution of good quality
seeds; and
e) provide the local industry protection against
unfair competition from imported seeds.

Republic Act 7308, otherwise known as the Seed Industry
Development Act was enforced in 1992.
The Bureau of Plant Industry then had been in the
forefront before a bill relevant to Seed industry was
enacted and became a law.

Reproductive Structures
of Flowering Plants

Reproductive Structures
of Flowering Plants
 Flowers are the reproductive shoots of
angiosperm sporophytes
 Spores that form by meiosis inside
flowers develop into haploid
gametophytes

Stamens
 Stamens consist of a filament with an anther
at the tip
 Anthers contain pollen sacs, in which diploid
cells produce haploid spores by meiosis
 Spores differentiate into pollen grains
(immature male gametophytes)

Carpels
 Flowers have one or several carpels,
each with a sticky stigma to capture
pollen grains
 The ovary contains ovules which
undergo meiosis to form a haploid
female gametophyte

Fig. 30-2a (2), p. 508
stamen carpel
(male reproductive part) (female reproductive part)
filament anther stigma style ovary
petal (all petals
combined are the
flower’s corolla)
ovule
(forms
within
ovary)
sepal (all sepals
combined are
flower’s calyx)
receptacle

Pollination
 Pollination: The transfer of pollen
from the male anther to the female
stigma

Why is Pollination
Important?
 Sexual reproduction is important for
evolution:
 Sexual reproduction produces variable
offspring, creating diversity and variation
among populations (shuffling of genes)
 You need variation for Natural Selection to
occur
 Sexual reproduction is advantageous to an
organism only if it happens with someone
other than itself!

Pollen Distribution
 Wind- not efficient and not spp.
specific
 Animals
Insects
Birds
Mammals
Reptiles
amphibians

Seed Formation
 After fertilization, mitotic cell
divisions transform the zygote into
an embryo sporophyte
 Endosperm becomes enriched with
nutrients
 Ovule’s integuments develop into a
seed coat
 Seed (mature ovule)
 An embryo sporophyte and nutritious
endosperm encased in a seed coat

Seeds as Food
 As an embryo is developing, the parent
plant transfers nutrients to the ovule
 Humans also get nutrition from seeds
(grains)
 Embryo (germ) contains protein and
vitamins
 Endosperm contains mostly starch

Seed Dispersal
 Fruits function to protect and
disperse seeds
 Fruits are adapted to certain
dispersal vectors:
 Mobile organisms such as birds or
insects
 Environmental factors such as wind or
water

Stages of Embryo
Development in Monocot
 Zygotic stage.
This single-
celled stage
follows fusion
of the haploid
egg and sperm.

Stages of Embryo
 Globular stage. This
stage occurs 2–4 DAP
(days after pollination).
Following an initial
horizontal division to
create the apical and
basal cells, a series of
variable cell divisions
create a multilayered,
globular embryo.

Stages of Embryo
 Coleoptile stage.
At 5 DAP, the
coleoptile
(specialized
tubular first leaf),
shoot apical
meristem , root
apical meristem,
and radicle
(embryonic root)
form.

Stages of Embryo
 . Juvenile
vegetative stage.
At 6–10 DAP,
the shoot apical
meristem
initiates several
vegetative
leaves

Stages of Embryo
 Maturation
stage. During
11–20 DAP, the
expression of
maturation-
related genes
precedes the
onset of
dormancy

Carbohydrate Stored in
Seeds
 Carbohydrate is the major storage
substance in seeds of most cultivated
plants.
 Cereals are especially rich in
carbohydrates and low in fats and
proteins.
 Starch and hemicellulose are the major
forms of carbohydrate storage in seeds.

What are Carbohydrates?
 class of organic macromolecules made up of
carbon, hydrogen and oxygen and are often
called "sugars and starches"
 There are three classes of carbohydrates,
based on the number of sugar units:
 1) Monosaccharides
 2)Disaccharides
 3) Polysaccharides

 There are three types of starch:
 (1) Amylose: a non-branching straight
chain of glucose - used to store glucose in
plants.
 (2) Amylopectin: a branched chain, also
used to store glucose in plants.
 (3) Glycogen: another branched chain
molecule used to store glucose in animals.

Hemicellulose
 other major form of carbohydrate storage in
seed.
 hemicellulose is usually found in the cell walls
of plants, they are also found as reserve food
material.
 includes xylans, mannans and galactans.
 found in the thickened tertiary layers of cell
wall of the endosperm in cotyledons

Mucilages
 complex carbohydrates consisting of
polyuronides and galacturonides which
chemically resemble the pectic
compounds and hemicellulose.
 become very sticky when wet and in
some cases it tends to cling on the
material that it touches. It is a seed
dispersal mechanism.


Pectic Compounds
 occur in seeds and in other plant parts, mainly as
components of the cell wall and the middle lamella
where they serve to bind the cell walls together
 propectins differ from pectins since they have larger
molecule chain
 when propectins are converted into pectins, they are
instrumental in softening of ripening fruits.

Lipids
 substances that are insoluble in
water but soluble in ether,
chloroform, benzene or other fat
solvents
 either esters of fatty acid and
glycerol or their various hydrolytic
products
 known as glycerides or more
especially as triglyceride, because
each glycerol molecule is combined
with three fatty acid molecules

 Fatty acids are so
named because they
are constituents of
natural fats and in the
free state, they
resemble fats in
physical properties.
 Free fatty acids are
seldom found in plant
parts other than in
germinating or
deteriorating seeds as
a result of fat
hydrolysis.

 Glycerol and other alcohols are
combined with fatty acids to form
different kinds of lipids.
Of these, trihydroxy alcohol and
glycerol or glycerine are mostly
often involved and form esters
(glycerides) with many different
fatty acids.


Proteins
 Proteins are nitrogen-containing molecules of huge
size and exceedingly complex structure; the greater
part of which yield amino acids upon hydrolysis.
 Proteins comprise a valuable food storage
component in seeds of most plant species.
 Soybeans are one of the few species known in which
protein comprises more of the reserve food supply
than do fats or carbohydrates.
 Most of the plants known to have high protein seed
are legumes having nitrogen-fixing capacity.

Storage Proteins
 Storage stored in specialized structures
called protein bodies which are located in
cotyledons and endosperm of the seed
 Enzymes (proteinases) are required to
catabolize storage proteins into amino
acids which in turn can be used by the
developing embryo for new protein
synthesis
 These enzymes can be present in stored
forms in the dry seed, but the majority of
proteinases are synthesized as new
enzymes following imbibition.

Proteins
 Proteins are nitrogen-containing molecules of huge size and
exceedingly complex structure; the greater part of which yield
amino acids upon hydrolysis.
 Proteins comprise a valuable food storage component in seeds
of most plant species.
 Soybeans are one of the few species known in which protein
comprises more of the reserve food supply than do fats or
carbohydrates.
 Most of the plants known to have high protein seed are legumes
having nitrogen-fixing capacity.

Functions of Protein
 Physiological functions of protein
include:
 act as enzymes that catalyze
biochemical reactions
 structural or mechanical functions
 involved in cell signaling and transport
through membranes

Seed Proteins
 In seeds, the greatest quantity of proteins is found in storage
proteins.
 Many of the enzymes present in seeds are essential for
storage reserve utilization by the embryo during the
germination process.
 There still remain many diverse proteins that have structural
(e.g., components of cell membranes and walls) or metabolic
functions (e.g., enzymes and transporters)
 Some proteins found in seeds also provide protection against
pests and pathogens.

Storage Proteins
 Storage proteins are stored in specialized structures
called protein bodies which are located in cotyledons
and endosperm of the seed
 Enzymes (proteinases) are required to catabolize
storage proteins into amino acids which in turn can be
used by the developing embryo for new protein
synthesis
 These enzymes can be present in stored forms in the
dry seed, but the majority of proteinases are
synthesized as new enzymes following imbibition.

Four Classes of Seed Proteins
 1) Albumins, soluble in water at
neutral or slightly acid pH. This
fraction is primarily enzymes.
 2) Globulins, soluble in saline
solution, but insoluble in water
 3) Glutelins, soluble in acid or alkali
solutions
 4) Prolamins, soluble in 70-90%
ethanol

Corn Protien
 In maize seeds, zein (a prolamin) is the most
abundant storage protein.
 Zein is relatively rich in alanine and leucine, with
low levels of lysine and almost no tryptophan.
 Thus, maize protein is of poor quality if used as the
only protein source in monogastric
animal nutrition.
 Zein is primarily stored in protein bodies in the
maize seed endosperm.

Legume Protein
 The percentage of protein
concentration in dicotyledonous
seeds is high, with soybean and other
legume seeds ranging from 25 to
50% compared to only 10 to 15% in
cereal seeds.

Other chemical compounds found in
seeds Alkaloids
 Alkaloids are chemically heterogeneous organic
compounds containing nitrogen.
 Alkaloids may also serve as protective mechanisms of
seeds against pests and
pathogens because of their bitter flavor.
 Alkaloids can be classified according to their
molecular structure.

Other chemical compounds found in
seeds
 Tannins are groups of complex astringent polyphenolic
compounds occurring widely
in plants.
 Tannins are especially common found in tree bark,
unripe fruits, and leaves.
 They also occur in seeds, particularly in the seed coat.
Examples of seeds containing tannins are cocoa, many
legumes (especially red and black beans), pecans,
cashews and walnut.

Seed Germination
© 2008 Paul Billiet ODWS

Seed maturation
 Takes place in the fruit on the parent plant
 Endospermous seeds: Retain the endosperm tissue,
which eventually dies but it is surrounded by a
layer of living cells, the aleurone layer.
 Non-endospermous seeds: The endosperm tissue is
absorbed by the cotyledons. These then become
the food reserve for the seed.

Endospermous Seeds
 The single massive
cotyledon is termed the
scutellum, while the
plumule and radicle are
enclosed by protective
structures termed the
coleoptile and the
coleorhiza.

Endospermous Seeds
 Endospermic seeds are seeds whereby the
endosperm is present in the mature seed and serves
as food storage organ.
 In an endospermic seed, the embryo is small
compared to the volume of the seed, with the rest
of the space being occupied by the endosperm.
 A good example is the wheat seed where the bulk
of the seed is endosperm (the starch we use as
food) and the embryo is a small shield-shaped thing
at one side, the so-called "wheat germ".

Non Endospermous Seeds
 The cotyledons serve as sole
food storage organs.
 During embryo
development the cotyledons
absorb the food reserves
from the endosperm.
 The endosperm is almost
degraded in the mature
seed and the embryo is
enclosed by the testa.

Non Endospermous Seeds
 Examples: rape (Brassica
napus), and the legume family
including pea (Pisum sativum),
garden or French bean
(Phaseolus vulgaris), soybean
(Glycine max)

Seed viability
 Viability: When a seed is capable of germinating
after all the necessary environmental conditions are
met.
 Average life span of a seed 10 to 15 years.
 Some are very short-lived e.g. willow (< 1 week)
 Some are very long-lived e.g. mimosa 221 years
 Conditions are very important for longevity
 Cold, dry, anaerobic conditions
 These are the conditions which are maintained in
seed banks

Germination: The breaking of dormancy
The growth of the embryo and its penetration of the seed coat
Break down of barriers
Abrasion of seed coat (soil
particles)
Decomposition of seed coat
(soil microbes, gut enzymes)
Cracking of seed coat (fire) Change in physical state -
rehydration
Destruction and dilution of
inhibitors
Light, temperature, water
Production of growth
promoters© 2008 Paul Billiet ODWS

Germination
STAGE EVENTS
PREGERMINATION (a) Rehydration – imbibition of water.
(b) RNA & protein synthesis stimulated.
(c) Increased metabolism – increased respiration.
(d) Hydrolysis (digestion) of food reserves by
enzymes.
(e) Changes in cell ultrastructure.
(f) Induction of cell division & cell growth.
GERMINATION (a) Rupture of seed coat.
(b) Emergence of seedling, usually radicle first.
POST GERMINATION (a) Controlled growth of root and shoot axis.
(b) Controlled transport of materials from food
stores to growing axis.
(c) Senescence (aging) of food storage tissues.© 2008 Paul Billiet ODWS

Environmental factors affecting seed germination
Water
Temperature
Light
Gases

Water Requirement
 A seed must have an ample supply of moisture for
germination to occur.
 Moisture content needed for germination to occur
ranges from 25% to 75%.
 Once the germination process begins, a dry period or
lack of water will cause the death of the developing
embryo.

Problems associated with water
uptake (imbibition)
 Imbibition injury - due to too rapid water
uptake resulting in solute leakage
 The initial phase of water uptake is very rapid.
 Because the process of drying causes
membranes to become ‘leaky’ there is a risk
that sugars and electrolytes can leach out the
seeds during this period of rapid uptake
before the membranes have restored their
normal function.

The effect of temperature on
germination
 Speed of germination.
 Range of temperatures over which germination
 can occur.
 Seasonal physiological changes as seeds become
more or less dormant.

The effect of light on germination
 Most cases seeds are indifferent
 Many require light e.g. small-seeded
annuals
 Few are inhibited
 Seeds sensitive to duration, intensity
and especially quality
 All light responses controlled by
phytochrome

 Many growers believe that most seeds require
darkness for germination - this is wrong.
 In fact most seeds germinates equally well in
light or dark.
 Many seeds only germinate in the light and only
a a few will only germinate in the dark.
 Even in a single batch of seeds, the response
may vary depending on other environmental
factors. e.g. temperature.

The effect of gases on
germination Reduced O2 or elevated CO2 usually reduces
germination.
 Except some submersed aquatics where
germination is stimulated by anaerobic
conditions.
 Nitrogen dioxide gas may have potential for
dormancy breaking.

 Seed dormancy is a condition where seeds
will not germinate even when the
environmental conditions (water,
temperature and aeration) are permissive
for germination (Copeland and McDonald,
2001).
 Dormancy does not only prevent
immediate germination but also regulates
the time, conditions and place for
germination to occur.

Importance
 Seed dormancy provides a mechanism for plants to
delay germination until conditions are optimal for
survival of the next generation (Finkelstein et al. 2008).

 Creation of a “seed bank”.
 In nature, a seed banks ensures that not all the
sees for a species germinate in a single year.
 This is an insurance against years where
flowering or fruiting may not occur for some
catastrophic environmental reason.
 Some seeds remain dormant in a seed bank for
decades.

Ideally plants should be
preserved in the wild in the habitat
where they naturally grow.
However human-induced habitat
loss is already great and likely to
continue.
Seed banks are a very efficient
way of ensuring their survival.

Classification of Seed Dormancy
 Primary dormancy is the inability of seeds to
germinate even in the presence of environmental
conditions favoring it.
 Secondary dormancy is a type of dormancy
imposed by certain adverse environmental
conditions in previously nondormant seeds, or
seeds in which primary dormancy has been
broken.

Classification of Primary Dormancy
 Endogenous
• embryo characteristic prevents
germination
 There are two types of endogenous
dormancy – morphological and physiological.

Morphological Dormancy
 Morphological dormancy is where the embryo
has not completed development at the time the
seed is shed from the plant.
 The embryo must complete development prior
to germination.
 Seeds with morphological dormancy can have
either rudimentary or undeveloped embryos
(Atwater, 1980).

Morphological Dormancy
 Species with rudimentary embryos have little more than a
proembryo embedded in a massive endosperm.
 These are found in Ranunculaceae (Anemone, Ranunculus),
Papaveraceae,(Papaver, Romneya), and Araliaceae (Aralia,
Fatsia).
 Seeds with undeveloped embryos have embryos that are
torpedo shaped and up to one-half the size of the seed cavity.
 Important families and genera in this category include
Umbellifereae, (Daucus), Primulaceae (Cyclamen, Primula), and
Gentianaceae (Gentiana).

Overcoming Morphological Dormancy
 Warm temperatures (> 20oC) favor germination,
as does gibberellic acid treatment.
 Orchids have rudimentary embryos, but they are
not considered dormant in the same sense as
others in this category and special aseptic
methods are used for germination.

Physiological Dormancy
 This involves physiological changes within the embryo that
results in a change in its growth potential (Baskin and
Baskin 1971) that allows the radicle to escape the restraint
of the seed coverings.
 Physiological dormancy includes non-deep, intermediate
and deep categories. By far, endogenous, non-deep
physiological dormancy is the most common form of
dormancy found in seeds (Baskin and Baskin 1998).

What is after ripening?
 It is the period of usually several months of dry storage at
room temperature of freshly harvested, mature seeds and is a
common method used to release dormancy and to promote
germination (Bewley, 1997).
 In a broad sense, after-ripening describes the loss of the
dormant state in a seed over some period of time. In the
strictest sense, after-ripening refers to the loss of dormancy
mechanisms imposed by the Mother Plant
(http://www.seedimages.com/dormancy/dormancy-mechanisms.html).

 “After-ripening” is the time required for seeds in dry
storage to lose dormancy. It is the general type of
primary dormancy found in many freshly harvested seeds
of herbaceous plants (Atwater 1980; AOSA 1993, Baskin
and Baskin 1998).
 This type of dormancy is often transitory and disappears
during dry storage, so it generally not a problem by the
time the grower sows the seeds.

Photodormant seeds
 Seeds that either require light or dark conditions for
germination are termed photodormant.
 The basic mechanism of light sensitivity in seeds involves
phytochrome (Bewley and Black 1994, Taylorson and
Hendricks 1977).
 Exposure of the imbibed seed to red light (660 to 760
nm) usually stimulates germination, while far-red light
(760 to 800 nm) or darkness causes a physiological
change that inhibits germination (Van derWoude 1989).

Another Type of Primary Dormancy
 Exogenous dormancy is considered to be on the outside of
the seed; associated with the seed's external covering
structures such as the seed coat or pericarp.
 Classification of exogenous dormancy
 Physical - tissues impermeable to water (preventing seed
imbibition).
 Chemical -tissues contain chemical germination inhibitors.
 Mechanical- tissues restricting embryo expansion and
development.

 (1) inhibiting water uptake;
 (2) providing mechanical restraint to embryo
expansion and radicle emergence;
 (3) modifying gas exchange (i.e. limit oxygen to
the embryo);
 (4) preventing leaching of inhibitors from the
embryo; and
 (5) supplying inhibitors to the embryo (Bewley
and Black, 1994).
The tissues enclosing the embryo can
prevent germination by:

Breaking dormancy in hard seeds
 This type of dormancy allows dry seed to be successfully stored for
many years, even at warm storage temperatures.
 Germination in hard seeds can be increased by any method that can
soften or “scarify” the covering (Hartmann et al. 1997).
 Hardseededness can be variable in a population of seeds.
 It is increased by environmental (dry) conditions during seed
maturation, and environmental conditions during seed storage
(Baskin and Baskin 1998).
 Harvesting slightly immature seeds and preventing them from
completing desiccation can reduce hardseededness.

Classification of Physiological Dormancy
 Nondeep
 Intermediate
 Deep

Causes of Non Deep Physiological Dormancy
 Covering restricts oxygen
 Inhibitors in coverings
 Embryo cannot break through
physical barriers
 Endosperm restrict embryo growth

 Seed Scarification
 Any process of breaking, scratching, or
mechanically altering the seed coat to make it
permeable to water and gases is known as
scarification.
 In nature, this often occurs by fall seeding.
Freezing temperatures or microbial activities
modify the seed coat during the winter.
 Scarification can also occur as seeds pass
through the digestive tract of various animals.
Techniques to Break Nondeep
Physiological Dormancy

Intermediate Physiological Dormancy
 Excised embryos will grow
 As much as 6 months prechilling needed
 Gibberellins, kinetin, thiourea can shorten prechilling
requirement
 Acer negundo, Acer pseudoplatanus, Acer saccharum,
Corylus avellana, Fraxinus americana, Fraxinus
pennsylvanica, Fagus sylvatica
 Ethylene accelerated and increased germination at
15°C
 GA3 increased germination of unchilled seeds at 15°C,
10 weeks prechill negate chemical effect (Seed Sci
2004, p21-33)

Deep Physiological Dormancy
 Excised embryos do not grow or produce abnormal
seedlings (Prunus will)
 Long prechill requirement
 Chemicals do not affect germination of intact seeds
 Sorbus aucuparis – secondary dormancy induced above
20°C, germinates best at 1-3°C
 Acer platanoides, Acer tartaricum, Malus domestica,
 Prunus persica – 90 days prechill
 Prunus mahaleb – 100 days prechill
 3 to 5°C best germination temperature for Prunus
mahaleb, Prunus padus

Ways to stratify the seeds
 Cold stratification (moist-prechilling) involves
mixing seeds with an equal volume of a moist
medium (sand or peat, for example) in a closed
container and storing them in a refrigerator
(approximately 40oF).
 Periodically, check to see that the medium is
moist but not wet.
 The length of time it takes to break dormancy
varies with particular species; check reference
books to determine the recommended amount
of time.

Ways to stratify the seeds
 Warm stratification is similar to cold stratification
except temperatures are maintained at 68oF to
86oF, depending on the species.
 Warm stratification is for all intents and purposes
useful for advancing the softening of hard seed
coats (warm stratification is equivalent to the
seed sitting in warm soil/mud/leaf mold prior to
winter's onset;ie: often a whole summer season).

What is seed drying?
Drying is a normal part of the seed maturation
process.
Some seeds must dry down to minimum
moisture content before they can germinate.
Low seed moisture content is a pre-requisite for
long-term storage, and is the most important
factor affecting longevity.
Seeds lose viability and vigor during processing
and storage mainly because of high seed moisture
content (seed moisture greater than 18%).

Seed is a living hygroscopic material.
Relative humidity (RH) and temperature
of air influences seed moisture content.
If RH is more than the seed, the seed will
gain moisture.
If moisture within the seed is greater,
then vapour will move out of the seed.
Seed drying takes place when there is a
net movement of water out of the seed
into the surrounding air.
Principles of Seed Drying

A water potential gradient
is established between the
surface of the seed
and its internal tissues and
water begins to diffuse
along this gradient.
Water evaporates from the
surface of the seed at a rate
dependent on the water
potential difference
between the seed and the
surrounding air.
As the seed approaches
equilibrium with the
surrounding air the rate of
drying slows down
exponentially.
How seeds dry

Seed size and the resistance of the
surrounding 'seed coat' structures
have a marked effect on the rate of
drying.
Large seeds dry relatively slowly
compared with small seeds due to
the extended internal moisture
flow.
If large seeds with porous seed
coats are dried too quickly, the
large moisture differential between
the surface and internal layers of
the seed may cause structural
damage.

In some cases this can lead to a
collapse and shrinkage of the
seed coat, and the formation of
an impermeable barrier.
This may prevent further drying
and increase the risk of viability
loss due to ageing.
A thin layer of seeds will dry
more rapidly than a deep layer
due to more rapid diffusion of
water from within each seed to
the surface of the seed layer.

The faster the air speed,
the faster moist air will
be moved away from
the surface of the
seeds.
As an approximation,
drying time is halved
when the velocity of the
surrounding air is
doubled.

Effect of temperature
• Increased temp. →
decreased RH → increased
water potential gradient →
increased rate of diffusion
• Water evaporates more
quickly.
BUT, heat may reduce
viability of long term
conservation collections
Temperature affects the
drying rate in three ways.

Increasing air
temperature decreases
the RH which will
increase the rate of
diffusion of water to the
surface of the seed layer,
and hence the speed of
drying.
Moisture within the seed
diffuses more quickly to
the seed surface at
higher temperatures.

Raising the temperature will
always accelerate drying; a
10°C increase in temperature
approximately doubles the
rate of drying.
High temperatures are usually
employed to dry commercial
seed lots but will have an
adverse effect on seed
longevity specially if seeds are
wet.
In order to avoid unnecessary
losses during drying, seeds for
long-term conservation should
be dried with cool air.

Drying of seed is very important to
maintain their vigour and viability for
longer periods.
It prevent seed deterioration due to
increased microorganism activity,
heating and mold/fungal growth etc..
Importance of seed drying

In general for long term storage in the
gene banks the orthodox seeds should be
dried to 3-7% moisture content except
soybean.
In soybean like crops where low
moisture can adversely effect seed viability
the seeds are usually dried to 7-8%
moisture content.

Moisture increases the respiration rate of
seeds, which in turn raises seed temperature.
For example, in large-scale commercial seed
storage, respiring seeds may generate enough
heat to kill the seeds quickly, or to even start a
fire if not dried sufficiently.
Small-scale growers are not likely to have
such an extreme condition, but seed longevity
will, nevertheless be affected.
Problems associated with high seed moisture

Mold growth will be encouraged by moisture,
damaging the seeds either slowly or quickly,
depending on the moisture content of the seeds.
Some molds that don’t grow well at room
temperature may grow well at low temperatures
causing damage to refrigerated seeds.
In such a case there may be no visual sign of
damage.

Important considerations in seed drying
Seed with high initial moisture content should
not be exposed to extremes of temperatures.
Seed drying should not be done at high
temperatures
Seed should be dried gradually under low
temperature and low humidity

Several methods are available for drying the
seed.
For genebank samples drying should always be
done under low humidity conditions.
RH 10-15% and temperature of 15 C are
recommended by IBPGR Advisory Committee
on Seed Storage.

Methods of Seed
Drying
Sun drying
Forced air drying

Sun Drying
In the absence of forced air drying facilities, the moisture content of
seeds have to be reduced in the field before harvest, and later by sun
drying on the threshing floor.
The system involves harvesting of crops when they are fully dried in
the field, leaving the harvested produce in field for a couple of days to
sun dry and later spreading the threshed and winnowed produce in
thin layers on threshing floors to sun dry.
The main advantage of sun drying is that it requires no additional
expenditure, or special requirement.
The disadvantages are delayed harvest, risks of weather damage and
increased likelihood of mechanical admixtures.

Forced Air Drying
In this system air (natural or heated) is forced
into seeds.
The air passing through damp seeds picks up
water.
The evaporation cools the air and the seed.
The heat necessary for evaporating the water
comes from the temperature drop of the air.
This is the most fundamental principle of forced
air seed drying.
.

Simple & economical drying
Low temperature drying (40‐45ºC )
Simple to manage
Affordable & low level of integration for
low
capacity drying
Fast drying at small capacity (6‐12 hours)
Can be dried promptly at farm level
Requires labour to stir the grain during
drying
Able to use for other drying means, like
wheat,
seeds, beans, nuts, etc.
Fixed Flat Bed Batch Dryer

A dry room is the most expensive option, but
allows seeds to be left in a dry environment until
cleaning is practicable.
Moisture is removed from the incoming air,
using either sorption or refrigeration.
Sorption driers (using silica gel, lithium chloride
or molecular sieve types) tend to be more
electrically efficient at maintaining low RH
conditions than are refrigeration driers
Sorption driers generate heat and so need to be
used in conjunction with some cooling system.

Seed processing involves:
cleaning the seed samples of extraneous
materials,
drying them to optimum moisture levels,
testing their germination and
packaging them in appropriate containers
for conservation and distribution.
What is Seed Processing?

TYPES OF SEED PROCESSING
A.Dry Seed Processing
B. Wet Seed Processing

When seeds are ready to be processed, the
entire seedpod, capsule, or seed head will
become brown and dry.
During the maturation process, the ripening
pods and capsules change color from green, to
yellow green, to yellow, to light brown, to a
darker brown, or dark gray.
Ripening and maturation may be uneven within
the pod or capsule, uneven on the plant, and
uneven within the stand of plants.
Dry seed processing (pods, capsules, seed
heads, etc.

One method of dealing with crops that mature their seed
unevenly is to pull the plants and hang them upside down
to dry under cover.
This allows the seed to continue to mature on the plant
while the plant dries.

After harvest, seeds are threshed to remove the
seed from the surrounding plant material.
A period of air-drying is important before seeds
are threshed.
Plant material should be spread out in thin
layers until all plant material is dry; otherwise,
mold, decay, and heat from decay will cause
damage to the seeds.

Wet seed processing is used with seed
crops that have seeds in fleshy fruits or
berries.
There are three steps to the process:
(1) extraction of the seed from the fruit,
(2) washing the seeds, and
(3) drying.
Wet seed processing (crops with fleshy
fruits, fermentation)

The type of extraction process depends on the species.
Soft fruits such as tomatoes are cut up, mashed, and then
fermented.
Cucumbers and melons are cut in half, the seed scraped
out along with the fruit pulp surrounding the seed, and
then fermented.
In watermelons, the entire fleshy fruit is fermented
along with the extracted seed.
These types of fruits have a gel surrounding the seed
that contains germination inhibitors.
The presence of the gel also makes handling and drying
of the seed difficult.

After fermentation is complete, the seeds are washed to
remove pulp, pieces of fruit and debris, and low quality
seed.
Before washing the seed, it is useful (especially for
washing tomato seed) to first scoop out pieces of pulp
floating on top of the mash.
This is done by straining the mash with your fingers,
pulling out the larger chunks.
Whether or not there is floating pulp depends on the
variety or how thoroughly the fruit was processed.
Seed Washing

Seed cleaning involves removal of debris, low quality,
infested or infected seeds and seeds of different species
(weeds).
Seed Cleaning

Importance of Seed Storage and Handling
Good seed is essential for successful crop
production, whereas poor seed is a serious farm
hazard .
It is important to store and handle seeds
properly after harvesting to ensure good
germination and purity specially, if we want to
use them the following season and to store both
unsold marketable and consumption seeds .

Improper drying and storage conditions
in handling seeds can have an adverse
affect on the life of those seeds.
Loss in viability, discoloration, toxin
production and growth of fungus can take
place rapidly if proper preventative
measures are not taken.

The safe storage of seeds is also important
for these reasons:
a. seeds must be preserved for use as human
and animal food
b. seed viability must also be protected
(germplasm protection) for various uses by
the plant scientists who maintain a permanent
reservoir of seed stock by establishing a seed
bank.

Three objectives for storing seeds
1. Very short period between collection and
sowing
2. Several years (10 or less) to ensure a reliable
supply of seeds in the absence of annual
crops
3. Long periods (10 to 50+ years) for germplasm
conservation

Factors Affecting Longevity of
Seeds
Seed Characteristics
Two groups based on their storage characteristics:
orthodox and recalcitrant (, Dr. E. H. Roberts ,1973 ).
Orthodox seeds are those that can be dried to moisture
contents of 10% or less; in this condition they can be
successfully stored at subfreezing temperatures.
Recalcitrant seeds, on the other hand, are those that cannot
be dried below relatively high moisture levels (25 to 45%)
and therefore cannot be stored below freezing.

Intermediate seeds can be dried to
moisture levels almost low enough to
meet orthodox conditions (12 to 15%)
but are sensitive to the low
temperatures typically employed for
storage of orthodox seeds.
Viability is retained usually only for a
few years.

Seed morphology
Seed morphology is important to the storage life of seeds
in the context of protection for the embryo.
The hard seedcoats of species of the Leguminosae help
maintain the low level of metabolism in these dry orthodox
seeds by excluding moisture and oxygen.
Hard, thick seedcoats, such as those of Carya Nutt., Cornus
L., and Nyssa L., help protect the embryos from mechanical
damage during collection and conditioning.
The thinner or softer a seed coat may be, the more likely
that the seed has a shorter storage life because of rapid
moisture uptake or bruising of internal seed tissues.

Chemical composition
General observations of seed behavior in storage
has suggested that chemical composition is an
important factor in longevity; for example, oily
seeds do not store as well as starchy seeds.
There is some evidence, however, that suggests
that the relative concentrations of particular
carbohydrates play key roles in desiccation
tolerance, a critical property in determining
storage behavior of seeds (Lin and Huang 1994).

Seed maturity
Seeds of many orthodox species that are
immature when collected (or extracted from
fruits) are likely to fare poorly in storage (Stein
et al., 1974).
The physiological basis for this effect is not
known, but it seems logical that immature
seeds have not been able to complete the
normal accumulation of storage food reserves,
develop all needed enzymes and/or growth
regulators, or complete their full
morphological development and cell
organization.

Seed Handling Prior to Storage
Poor fruit or seed handling that damages seeds
will often lead to reduced viability in storage,
especially in orthodox seeds.
The most common example of this is impact
damage
to seeds during extraction and conditioning.
Seeds can be bruised during processing, or poor
transport systems (Kamra, 1967).

Another factor to consider in damage to seeds
during extraction and conditioning is cracks or
other breaches of the seed coats that will allow
microorganisms to enter.
Cracks in seed coats that occur during seed
conditioning are usually not visible to the naked
eye but can be detected on radiographs .
This is one reason why hardseeded legumes are
usually not returned to storage after mechanical
scarification.

Storage Environment
Storage environment is obviously very important
in extending the life of seeds.
The general objective is to reduce the
metabolism of the seeds as much as possible
without damaging them and to prevent attack by
microorganisms.
The ideal metabolic rate in storage will conserve
as
much of the stored food reserves in the seeds as
possible, yet operate at a level that maintains the
integrity of the embryos.

Moisture
Seed moisture is the most important factor in maintaining
viability during storage; it is the primary control of all
activities.
Metabolic rates can be minimized by keeping seeds in a dry
state.
For true orthodox and sub-orthodox seeds, optimum
moisture contents for storage are 5 to 10%.
The normal practice with all orthodox tree seeds is to dry
them to these levels and store them in moisture-proof
containers that maintain them at these levels.

Temperature
Metabolic rates can also be minimized
with low temperatures, both for orthodox
and for recalcitrant seeds.
The storage moisture content determines
just how low temperatures can be set for
seed storage.
From freezing to –15 °C, 20% is the
approximate upper moisture limit.
Below–15 °C, the limit is about 15%; and in
cryogenic storage in liquid nitrogen (–196
°C), 13% is the limit.

Storage Facilities
Cold Storage
Facilities for seed storage will vary by the amount of seeds
to be stored and the projected length of storage.
Small seedlots— a liter (quart) or less—can be stored in
household refrigerators and freezers. Larger seedlots and
quantities will require a walk-in refrigerator or freezer .
These units are usually assembled from prefabricated
insulated panels and can be made almost any size to fit the
owner’s needs.
A suggested size for a nursery operation is one large
enough to hold a 5-years’ supply of seeds.

Orthodox seeds should be dried to safe moisture contents (5
to 10%) and stored in sealed containers that prohibit absorption
of moisture from the atmosphere.
The containers used most commonly for tree seeds are fiberboard
drums with a thin plastic coating on the inside .
These drums are available in different sizes they
hold approximately 25 and 50 kg (55 and 110 lb).
Any large, rigid container can be used, as long
as it can be sealed.
The best practice is to insert a polyethylene
bag liner for this purpose.
It is also a good idea to do this with fiberboard drums, as repeated
use of the drums over a number of years will cause breaks in their
interior plastic lining.
Containers

Moisture Control
Refrigerated storage units can be made with
controlled
humidity so that orthodox seeds can be stored in
unsealed containers without danger of moisture
absorption.
At the low temperatures usually employed for tree
seeds, however, this feature would be very
expensive.
It is much cheaper to dry the seeds and store them
in sealed containers.

Storage Recommendations
Orthodox Seeds
All orthodox seeds should be stored in moisture-
proof,
sealed containers with seed moisture contents of 5
to 10%.
If the period of storage will be 3 years or less for
true orthodox species, or 2 years or less for sub-
orthodox species, temperatures of 0 to 5 °C are
sufficient.
For longer periods of storage for both types of
orthodox species, freezers (–18 to –20 °C) should
be used.

Tropical-Recalcitrant Seeds
Storage of tropical recalcitrant seeds is done in
the same manner as storage of temperate
species, except that temperatures must be kept
at a high level.
There are differences among species but the
lower limits are generally 12 to 20 °C.
Successful storage for more than 1 year should
not be expected.

What is seed treatment?
Seed treatment refers to the application of fungicide,
insecticide, or a combination of both, to seeds so as to
disinfect them from seed-borne or soil-borne pathogenic
organisms and storage insects.
It also refers to the subjecting of seeds to solar energy
exposure, immersion in conditioned water, etc.

General Agronomic Recommendations
 Use certified or high quality seed: no old seed
prevent introduction of new diseases into your fields
prevent making an old problem worse
 Select best yielding cultivar for your area
adaptation and disease resistance
 Seeding date - know your diseases!
 Delayed seeding in fall may reduce amount of
Fusarium and crown root rot
 Delayed seeding in spring may reduce Pythium
infection

Benefits of Seed Treatment
Prevents spread of plant diseases
Protects seed from seed rot and
seedling blights
Improves germination
Provides protection from storage insects
Controls soil insects

Types of Seed Treatment
1) Seed disinfection: Seed disinfection refers to the
eradication of fungal spores that have become
established within the seed coat, or i more deep-
seated tissues.
For effective control, the fungicidal treatment must
actually penetrate the seed in order to kill the
fungus that is present.

2) Seed disinfestation: Seed disinfestation refers to
the destruction of surface-borne organisms that have
contaminated the seed surface but not infected the
seed surface. Chemical dips, soaks, fungicides
applied as dust, slurry or liquid have been found
successful.

3) Seed Protection: The purpose of seed protection
is to protect the seed and young seedling from
organisms in the soil which might otherwise cause
decay of the seed before germination.

1) Injured Seeds: Any break in the seed coat of a
seed affords an excellent opportunity for fungi to
enter the seed and either kill it, or awaken the
seedling that will be produced from it.
Seeds suffer mechanical injury during combining and
threshing operations, or from being dropped from
excessive heights. They may also be injured by
weather or improper storage.
Conditions under which seed must be treated

2) Diseased seed: Seed may be infected by disease
organisms even at the time of harvest, or may
become infected during processing, if processed on
contaminated machinery or if stored in contaminated
containers or warehouses.

3) Undesirable soil
conditions: Seeds are
sometimes planted under
unfavourable soil conditions
such as cold and damp soils, or
extremely dry soils.
Such unfavourable soil
conditions may be favourable to
the growth and development of
certain fungi spores enabling
them to attack and damage the
seeds.

4) Disease-free seed: Seeds are invariably infected, by
disease organisms ranging from no economic
consequence to severe economic consequences.
Seed treatment provides a good insurance against
diseases, soil-borne organisms and thus affords
protection to weak seeds enabling them to germinate
and produce seedlings.

Seed treatments
 Add recommended rate
 Overtreatment may lead to decreased emergence
 Undertreatment may not provide good control
 Undertreatment may lead to fungicide/insecticide
resistance
 Check labels for compatibility before mixing
insecticides and fungicides
 Some combinations are toxic to the seed

POLYMER COATING
What is polymer coating?
It is the process of coating the
seeds with polymers of different
colours along with nutrients and
plant protectants to increase the
aesthetic values of the seed
with required benefits.

Methodology
Coat the seeds with polykote (3 g
+ 5ml water / kg) after proper
dilution
Mix fungicide
and pesticide with the polykote
to increase the resistance to
the pest and diseases.
Shade the seed before using /
storing

RHIZOBIAL COATING
What is Rhizobial coating?
Rhizobial coating is to
enriching the rhizosphere
microenvironment with
organic nutrients for early
establishment.

Methodology
Take the seeds in a plastic tray
Add proper quantity of adhesive
(cool maida 10% gruel) to the seeds
or jaggery
Shake gently so that the adhesive
spreads evenly on all the seeds
Sprinkle the required biofertilizer
(Rhizobium, Azospirillum,
Azotobactor) evenly over the seeds
and continue shaking.
The wet seed surface will attract
the biofertilizer and result in even
coating over the seeds
Roll the seed for uniformity
Shade dry the seed
Lentil field in western Manitoba in which
plants on right received a commercial
rhizobial inoculant while plants on the
left were dependent upon endemic
naturalized population of rhizobia in the
soil for inoculation.

SEED PRIMING
What is seed priming?
Seed priming is a
physiologically based, seed
enhancement process for
improving the germination
characteristics of seeds.
Seed priming is
accomplished by partially
hydrating seeds and
maintaining them under
defined moisture,
temperature and aeration
conditions for a prescribed
period of time.

Advantages of seed priming
Enhances the germination
percentage
Enhances the speed and
uniformity of germination
Improves the resistance
towards water and temperature
stress
Increases the shelf life of seed
Highly suitable for small seeds
Enhances the yield
Field sown with primed
(right) and non-primed
seeds (left))

What is Seed Quality?
Seed quality indicates the seed’s ability to
germinate and establish “healthy” seedlings under
stressful conditions.
Germination and vigor are quick and inexpensive
lab tests that provide information about seed
quality.
Germination stated on the seed tag is what you
can expect under favorable moisture and
temperature conditions.

Why is Seed Quality Important?
Seed quality is critical in the establishment of
a uniform plant stand, the first step in producing a
successful crop, but good planting conditions are
also critical since even high quality seed can fail
under too much stress.

Healthy, high-quality seed is the first
prerequisite for abundant yield.
To get a good yield, good quality seed must
be sown.
The yield can increase with 5-20% when using
good quality seed!

The
advantages
of using good
quality seeds

Factors affecting seed quality

C. PHYSIOLOGICAL (Viability and Vigor)
Seed Viability refers to the capacity of a
normal seed to germinate and
produce a normal seedling.
Seed vigor comprises those seeds
properties which determine the potential
for rapid, uniform emergence, and
development of normal seedlings
under a wide range of field
conditions (AOSA, 1983).

Seeds have maximum quality at
physiological maturity.
After that, seed storage success
depends on environmental, harvest,
postharvest and storage conditions.

D. PHYTOSANITARY ATTRIBUTES (Insect
and Seed-borne Diseases)
Health of Seed refers primarily to the
presence or absence of disease-causing
organisms, such as fungi, bacteria,
viruses and insects.
Insects and fungi generally reduce seed
quality.

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