The document discusses the concept of seed vigour. It defines seed vigour as the state of active good health and natural robustness in seeds, which determine the potential level of rapid germination, normal growth and development of healthy seedling and stand establishment under a wide range of field conditions. It explains that a germination test alone is not adequate for predicting field performance as it is done under favorable laboratory conditions, whereas seed vigour tests can reliably predict stand-producing potential under field conditions. Various factors that affect seed and seedling vigour are also outlined, including genetic factors, seed size and maturity, environmental conditions during seed development, mechanical damage, and microbial infestation. Different methods for determining seed vigour, both physical

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Principles and Practices of Seed
Technology (3rd Year)
Govinda Raj Sedai
Fundamental concept
of seed vigour
MBMAN, Urlabari, Morang
@)&*.)#.!! (25 June, 2021)

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Concept of seed vigour:
It has been noticed that seed lots of similar germination percentage
gave varying results in regards to field stand. A germination test is
inadequate as far as prediction of plant stand establishment is
concerned. This is primarily due to the fact that the germination test
is carried out in seed testing laboratory under very favorable
artificial conditions, which are seldom available in the field.
Under laboratory conditions the weakest seed can also germinate
since it receives favorable moisture, temperature and substrate,
which is not loaded with microorganisms, herbicides, fertilizer,
fungicide or systemic insecticide. Seed lots of equal quality (basis of
germination test) will produce differential response in field
emergence. Vigour test could reliably predict stand-producing
potential of seed lots in the field condition. The ultimate proof of
any vigour test is its reliability in predicting field stands under a
variety of field conditions.

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Seed vigour can be defined as the state of active good
health and natural robustness in seeds, which
determine the potential level of rapid germination,
normal growth and development of healthy seedling
and stand establishment under a wide range of field
conditions is considered as seed vigour. It is a quality
dependent on physiological potentiality, germinability
and performance in field with respect to percentage,
rate and uniformity of seedling emergence which have
indirect influence on maintenance of crop stand at harvest
and yield.
Seed vigour :

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Seed vigour means, plant like …

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• List and explain different factors affecting plant density and crop
yield.
– agro-climate, - Variety,
– Seed quality - sowing time,
– water status, - weed competition,
– pest infestation, - nutrients status,
– Management level (precision, accurate & average)
• Explain seeding and stand establishment. Explain seed quality
and seedling emergence.
• List and explain the effects of seedling emergence on crop yield.
• Explain seed quality and post emergence growth.
• Explain seed quality and crop yield.
Influence of seed quality on crop establishment,
growth and yield

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Adverse effect of using low vigour seed
When we used the low vigour seed as seeding material the
following effects may be observed:
1. Stand of seed bearing plant may be reduced.
2. There will be delayed and reduced emergence of seedlings.
3. Plants will be dwarf with thin stems.
4. Number of nodes may be reduced.
5. There may be the reduction of leaf area and tillering.
6. The panicle length may be reduced in case of rice, wheat,
barley etc. and its exertion and anthesis will also be
delayed.
7. There may be delayed maturity of the crop.

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Methods of determining seed vigour
1. Physical test method: Seed size, seed density, physical soundness etc.
2. Performance test in optimum condition: First count, speed of
germination, seedling growth rate, seedling length, root and / or shoot
length, dry matter production, strong and weak seedling, vigour index
length, vigour index mass, seed metabolic efficiency (SME), mobilization
efficiency (ME).
3. Stress test: Accelerated ageing test, brick gravel test (Hiltner test),
paper piercing test, compact soil test, pathogen infested soil test, low or
high pH test, cold test, cool germination test, exhaustion test, water
sensitivity test, osmotic stress test, oxygen stress test.
4. Biochemical test:
Electrical conductivity test, tetrazolium test, respiration test, glutamic
acid decarbo-oxylase activity (GADA) test, mitochondrial efficiency,
volatile aldehyde test, free fatty acid test.

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Factors affecting seed and seedling vigour
1. Genetic control or genotypic effect
2. Seed size and density
3. Seed maturity
4. Timing of harvest
5. Temperature and moisture availability during seed
development
6. Soil fertility during seed development
7. Mechanical damage
8. Attack of microorganisms
9. Chilling injury during imbibition

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Factors affecting seed and seedling vigour
i) Genetic control or genotypic effect:
• The competence of a genotype in a particular
environment determines seed vigour.
• The difference in vigour exist among different species,
different varieties and even within a variety.
• The influence of genetic control of seedling vigour is
found in hybrid and polyploid plant over inbred and
diploid plants of the same species.
• For example seeds of barley hybrids have been found
to germinate faster, grow faster and exhibit a higher
respiration rate than either parent (McDainel, R.G.
1969).

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ii) Seed size and density:
Seed size also plays an important role in controlling vigour
of different crops. The superior performance of graded
large seeds of jute in respect of field emergence, better
crop stand at harvest and fibre yield than the small size
seeds have been reported by Ghos and Sen in 1981.
Similarly Kalakannavar et al(1989) reported that large
wheat seeds had increased germination percentage, rate
of field emergence as well as the root length, dry weight
and vigour index of seedlings. The size of seed and
accumulation of nutrition stored in it are controlled
genetically under a high genotype, environment
interaction. Seed density may also be positively correlated
with seedling vigour and plant performance.

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iii) Seed maturity :
As a seed matures, it's potential for rapid and vigorous
germination increases. Fully mature seeds have the potential of
complete physical and physiological development needed for
maximum expression of vigour. Seeds of most of the crop plants,
which can be dry, stored at low moisture level and cool storage
condition (orthodox seed) can maintain seed vigour for a long
time. Complete seed maturity is sometimes considered as the stage
of seed development, which produces maximum seedling vigour
under adverse germination conditions.
iii) Timing of harvest:
In plants with determinate flowering, seed maturity is relatively
uniform and the seeds mature at the same time but in case of
indeterminate flower (sugarbeet, carrots) harvest at any time
yields seeds with varying stages of maturity and these seeds have
low germination and low seed vigour.

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iv) Temperature and moisture availability during seed
development:
• Air temperature and soil moisture availability during seed
development of most of the crop species are affected on seed
size, yield, germination as well as seedling vigour and
subsequent yield.
• Water availability during seed development may influence seed
vigour indirectly through its influence on the chemical
composition of the mature seed.
• For example N content (protein) of cereal seed generally
decreases as the amount of water supplied during the
vegetative development of the parent plant increases.
• Temperature influences developmental processes, which in turn
influences seedling vigour. For example sugarbeet seeds
matured at higher temperature (i.e. 35oC) germinated more
rapidly than those matured at lower temperatures (30o).

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v) Soil fertility during seed development:
The fertility of the soil in which a plant grows influences the
chemical composition of the developing seed and
consequently its metabolism and vigour during germination.
A comprehensive study of fertility and seedling vigour in wheat
showed definite influence of fertility supplied to the parent
plant and subsequent seedling vigour. It appears that N and
P2O5 availability can influence seed development and
seedling vigour, but their effect varies among species and is
highly dependent on the stage of growth and environmental
conditions. The inorganic nutrients stored in the seed provide
valuable reserves during the early germination stages, which
can be especially critical for seedling establishment in soils that
are low in nutrients.

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vi) Mechanical damage:
The mechanically damaged (cracked and broken) seeds may
appear normal but exhibit less vigour than undamaged
seeds. It is due to the physiological deterioration triggered
by impact or it may be purely physical damage as a result of
cryptic, microscopic breaks at crucial locations within the
seed. For example seedlings from mechanically damaged
bean seeds may be morphologically normal but exhibit
slower germination, reduced growth rate, delayed maturity
and reduced yield (Barriga, C. 1961). Each handling process
throughout threshing, cleaning, treating, bagging,
transplanting and planting may cause impaction of seeds
against other seeds or hard metal surface and result in injury.

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vii) Attack of microorganisms:
Infestation by microorganisms causes deterioration of
seeds in storage and may further reduce seedling vigour by
attacking the germinating seedlings. Many species of fungi
that are normally saprophytic can become parasitic on
young seedlings. Fungal growth may be enhanced by
substances leached from the germinating seed. For
example damping off in beans may be due to stimulation
of Pythium and Rhizoctonia growth by nutrients leached
from the seeds.

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viii) Chilling injury during imbibition:
Seeds of many warm season species are especially
susceptible to low temperature injury during moisture
imbibition and early seedling growth. Such injury may
have immediate as well as delayed season long effect. For
example: imbibition of low moisture soybean seed at 5oC
was reported to cause a reduction in seedling survival, dry
matter accumulation and seedling height (Obendorf, R. L.
and P. R. Hobbs, 1970).

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Onion and cauliflower field

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