Historical Paper - Volume 2 2008 - International Seed Testing ...

H.A. JENSEN
Blowing has also been used as an aid in purity testing of temperate grasses. The
blowing point, for which no empty seeds were left in the heavy fraction after blowing
the working sample for 3 minutes, was found for the grasses Lolium perenne, Lolium
multiflorum, Festuca pratensis, Festuca rubra, Festuca ovina, Poa nemoralis, Agrostis
sp. and Cynosurus cristatus. Blowing before the purity separation saved time, as only the
light fraction needed to be inspected under reflected light for empty or undeveloped seeds
(Jensen 1979e, 2000).
5.9.5 Development of blowers
The introduction of blowing of grasses in Ottawa was associated with the development
of the Ottawa Seed Blower and the Iowa Air Blast Seed Separator. Other types were
the South Dakota Seed Blower, Burrows Model, the Hearson Blower, the General Seed
Blower and blowers produced in England, the Netherlands and Sweden.
The General Seed Blower became part of the standard equipment in many seed
laboratories. In the ISTA Rules multiplication of the blower setting of Poa pratensis by
the factor 0.82 is prescribed for purity test of Poa trivialis and for small seeded varieties
of Poa pratensis; this factor applies for General Seed Blowers only.
5.10 Testing chemically treated seeds
Chemical treatment of the grasses Poa and Dactylis is requested from time to time. If
the chemical treatment affects the blowing characteristics of the seed, the purity test of
the sample must be performed by the hand method. Since 1995 the ISTA Rules have
specified that the purity test and pure seed for germination of the species, tested by the
standard blowing method, shall not be blown, but analysed by the hand method, and a
sentence printed on the certificate, for example: Because of the chemical treatment, the
pure seed used for the germination was obtained by the hand method.
6. Workshops and other training activities
6.1 Workshops
ISTA Purity Workshops were held at:
• Cambridge, United Kingdom 1967 (Slettenhaar 1968)
• Lyngby, Denmark 1973 (Anonymous 1974)
• Wageningen, the Netherlands 1978 (Anonymous 1979)
• Cambridge, United Kingdom 1985 (Tonkin 1985)
• Angers, France 1994 (Jensen 1995)
• Budapest, Hungary 1997 (Ashton 1997, Jensen 2000).
The ISTA Workshops have been very important for the development and implementation
of the Rules for purity analysis and determination of other seeds by number as well as for
the identification of problems and the preparation of new proposals for Rule changes.
22