Physical purity analysis tells us the proportion of pure seed component in the seed lot as well as the proportion of other crop seed, weed seed and inert matter by weight in percentage for which Seed Standards have been prescribed. Thus, it helps in: Improving the plant stand (by increasing the pure seed component). Raising a pure crop (by eliminating other crop seed and weed seeds). Raising a disease free-crop (by eliminating inert matter). In the use of seed drill (by selecting uniform particles).

1. Physical purity analysis of
samples of different crops
Presented By:
W. Jupiter Singh
Department of Horticulture
ANNAMALAI
UNIVERSITY

2. Physical Purity Testing
Physical purity analysis tells us the proportion of pure seed
component in the seed lot as well as the proportion of other crop seed,
weed seed and inert matter by weight in percentage for which Seed
Standards have been prescribed.
Thus, it helps in:
Improving the plant stand (by increasing the pure seed component).
 Raising a pure crop (by eliminating other crop seed and weed seeds).
Raising a disease free-crop (by eliminating inert matter).
In the use of seed drill (by selecting uniform particles).

3. need for physical purity analysis
 Seed Certification or Seed Law Enforcement Agencies to judge
that the seed lot conforms to the prescribed standards.
Seed processing plants for using right kind of processing
equipment.
Physical purity analysis is a pre-requisite for germination test
because 'pure seed' component is used for germination testing.
Objective
The primary objective of physical purity analysis is to determine
i) the percentage composition by weight of the sample being
tested and by inference the composition of seed lot
ii) the identity of various species of seeds and inert particles
constituting the sample.

4. The pure seed shall refer to the species stated by the
sender, or found to Predominate the test, and shall include all
botanical varieties and cultivars of that species (even if immature,
undersized shriveled disease or germinated providing. They can be
definitely identified as of that species) unless transformed into
visible fungal-sclerostia, smut balls or nematode galls.
Pure seed shall include
a)intact seed units (commonly found as dispersal units
i.e. achenes and similar fruits, schizocarp, florets etc)as defined for
each genus or species
b) pieces of seed units larger than, one half their original size.
Pure Seed

5. exceptions made for particular genera or speciesexceptions made for particular genera or species
 seed units of families Leguminaceae, cruciferae, cupressaceae,
Pinaceae and Taxodiaceae with the seed coat entirely removed shall be
regarded as inert matter. Separated cotyledons of legumanoceae are
regarded as inert matter.
In certain genera of family gramineae.
a) A minimum size of caryopsis is required i.e. in Lolium, Festuca and Elytrigia
repens a floret with a caryopsis 1/3 rachilla is regarded as pure seed, but a
caryopsis less than 1/3the length of palea is regarded as inert matter.
a) The presence of caryopsis in spikelets and florets is not always obligatory.
b) The separation of pure seed and inert matter is done by uniform blowing
procedure.
This method is obligatory for Poa protensis and Dactylis glomerata.
c) Multiple seed unit is (MSU) are left intact in the pure seed fraction
e.g. Doctylis and Festuca.
d) Attached sterile florets are not removed, but left attached and included in the
pure seed fraction .
e.g. Arrhenatherium, Avena, Chloris, Dactylis, Festuca, Holens, Poa,
Sorghum and Triticum spelta.
a) For certain genera appendages are left on the seed but reported if found to the
extent of 1% or more, the percentage of such material must be shown on
Analysis certificate (example -paddy).

6. URE SEED DEFINITIONS APPLICABLE TO SPECIFIC GENER
GramineaeGramineae
Oryza(Paddy)
Spikelet, with glumes,lemma and palea enclosing a caryopsis including the
awn irrespective of its size.
Floret,with or without lemmas,with lemma and palea enclosing a caryopsis
including the awn irrespective of its size.
Caryopsis
Piece of caryopsis larger than one-half the original size.
Hordeum(Barley)
Floret,with lemma and palea enclosing a caryopsis with or without awn or
with or without rachis segment irrespective of their length.
Piece of floret containing a caryopsis larger than one-half the original size.
Caryopsis
Piece of caryopsis larger than one-half the original size.
Triticum, Zea,Secale (Wheat,Maize,Triticale)
Caryopsis
Piece of caryopsis larger than one-half the original size.

7. Avena (Oat)
Spikelet with lemma and palea enclosing a caryopsis, with or without awn
plus attached sterile floret.
Floret with lemma and palea enclosing a caryopsis, with or without awn.
Caryopsis
Piece of caryopsis larger than one-half the original size.
Sorghum(Jowar)
Spikelet, with glumes, lemma and palea enclosing a caryopsis with or
without hyaline palea or lemmas,rachis segments padicle(s),awn(s),attached
sterile or fertile floret(s).
Floret, with lemma and palea ,with or without awn.8
Caryopsis.
Piece of caryopsis larger than one-half the original size.
Pennisetum (Pearlmillet)
Fascicle of 1-5 spikelets(spikelets with glumes, lemma and palea
enclosing a caryopsis, plus attached sterile lemma) with involucre of
bristles.
Floret with lemma and palea enclosing a caryopsis.
Caryopsis.
Piece of caryopsis larger than one-half the original size.

8. Leguminosae : Seed, provided a portion of the testa is attached.
Exceptions: Piece of seed larger than one-half the original size, provided a
portion of the testa is attached.
Raphanus:
One-seeded segment of pod or siliqua , with or without stalk or terminal
beak.
 Seed, provided a portion of testa is attached.
Piece of seed larger than one-hair the original size, provided a portion of
testa is attached.
Gossypium
 Seed with or without testa.
Piece of seed larger than one-half the original size, with or without testa.
(NB: testa with or without hairs).
Cruciferae
MalvaceaeMalvaceae

9. Schizocarp is a dry fruit which separates into two or more units(mericarps)
at maturity.
Piece of mericarp larger than one-half the original size unless it is obvious
that no seed is present.
Seed with the pericarp partially or entirely removed.
Piece of seed larger than one half the original size, with the pericarp
partially or entirely removed.
Seed,with or without tesla, with or without strophiole/caruncle.
 Piece of seed larger than one-half the original size, with or without testa.
Cluster or piece of cluster, including attached stalk pieces (protruding stalk
pieces that are longer than the width of the cluster, are to be entirely
removed)retained on a 200 mm x 300 mm rectangular sieve,with square ended
slots1.5mmx20mm when shaken for one minute, with or without seed.
Umbelliferae (Carum, Coriander, Cumin, Carrot, Fennel)Umbelliferae (Carum, Coriander, Cumin, Carrot, Fennel)
Euphorbiaceae (Ricinus)Euphorbiaceae (Ricinus)
Chenopodiaceae(Spinach,Beet,Sugarbeet,Red beet).Chenopodiaceae(Spinach,Beet,Sugarbeet,Red beet).

10. It includes seed like structures, stem pieces, leaves, sand particles, stone
particles, empty glumes, lemmas, paleas, chaff, awns, stalks longer than
florets and spikelets.
Other crop seedOther crop seed
Weed SeedWeed Seed
It refers to the seeds of crops other than the kind being examined.
It includes seeds of those species normally recognized as weeds or specified
under Seed Act as a noxious weed.
Inert matterInert matter

11. a) Soil divider
b) Boerner divider (work on gravitational force)
c) Gamet divider(work on centrifugal force and electrically operated)
Equipments required
Soil divider Boerner divider Gamet divider
1.Dividers1.Dividers

12. 2.Balance:2.Balance:
Electric or electronic balance are better
due to their accuracy and quickness
3.Blower3.Blower

13. Diaphnoscope using reflected light are
used to separate inert matter such as
empty florets of grasses
4.Diaphnoscope 4.Diaphnoscope
5.Sieves.5.Sieves.
6.Sample pans, dishes, forceps, spatula and hand lens
7.seed herbarium 0f crop and ,weed seed
6.Sample pans, dishes, forceps, spatula and hand lens
7.seed herbarium 0f crop and ,weed seed

14. Procedure
Place the sample on the purity work board after sieving / blowing
operations and separate into other crop seeds and inert matter.
After separation, identify each kind of weed seeds, other crop seeds as to
genus and species.
The names and number of each are recorded.
The type of inert matter present should also be noted.
Figure : Purity test laboratory
Obtaining Working sample and SeparationObtaining Working sample and Separation

15.  All the four components must be weighed to the required number of
decimal places.
 The percentages of the components are determined as follows.
% of components = __________________________ X 100
Total weight of all
If there is a gain or loss between the weight of the original samples and the
sum of all the components is in excess of one percent, another analysis
should be made.
CalculationCalculation
components
Weight of individual component

16. If the analysis result is near the border line in relation to the seed standards,
one more test is done and the average is reported.
However, if a duplicate analysis is made of two half sample or whole
samples, the difference between the two must not exceed the permissible
tolerance.
If the difference is in excess of the tolerance, analyze further (but not more
than 4 pairs in all) until a pair is obtained which has its member within
tolerance.
It is required in certain crops like sunflower and paddy.
400 seeds taken from the pure seed and the number of seeds without husk
are counted (partly huskless seeds are excluded)
 % is calculated as
% of huskless seeds = ________________________ X100
400
Duplicate testsDuplicate tests
Determination of huskless seedsDetermination of huskless seeds
Number of huskless seeds

17. Reporting resultsReporting results
The result of a purity analysis shall be given to one decimal place and the
percentage of all components must total 100.
Components of less than 0.05% shall be reported as ‘Trace’.
If the result for a component is nil, this must be shown as ‘0.0’ in the
appropriate space.
1. Name and address of the issuing laboratory
2. Name of responsible individual
3. Laboratory test sample number
4. Date report of analysis is issued
5. Application information, such as kind of seed, cultivar, lot number, lot size,
certification
number, treatment, etc.
6. Kind of pure seed by common name as cited in the Plant Improvement Act
7. If submitted sample is treated, inoculated, film coated, coated, encrusted, or
pelleted
8. Weight of purity working sample
Laboratory reports of purity analysis performed in accordance with the rules
should include:
Laboratory reports of purity analysis performed in accordance with the rules
should include: