Agriculture Reference
In-Depth Information
filter Paper
Filter paper is often used in petri dish tests, but it is also used in larger germination boxes (Fig. 5.4). The
AOSA rules specify that P = covered petri dishes with (a) two layers of blotters, (b) three thicknesses of
ilter paper, or (c) on top of sand or soil. Speciications for ilter paper are that it be white, with a bursting
strength of not less than 12 points, an absorptivity of not less than a 2 1/2-inch rise of water in 5 minutes
for a vertically suspended 1/2-inch strip immersed in water to a one-inch rise of water in 5 minutes for a
vertically suspended 1/2-inch strip immersed in water to a one-inch depth, 100% rag composition, not more
than 0.2% ash, pH from 6.0 to 7.5, and be free from toxic chemicals.
Whatman No. 2 ilter paper or its equivalent is considered a satisfactory substratum in petri dishes.
Procedures for wetting and maintaining proper moisture for ilter paper are the same as those described for
blotters.
Figure 5.4. Ryegrass seedlings germinated for 7 days on white ilter paper to observe the luorescent roots.
Note the vertical orientation of seedlings.
Creped Cellulose Paper
Many laboratories use creped cellulose paper (Kimpak or Versa-Pak) as a substrate for germination test-
ing. It is primarily used for large seeded species such as soybean, velvetbean, ield and sweet corn, lima
bean, broad bean, and several large seeded tree species. It is especially effective in retaining moisture and
provides for more normal vertical orientation of seedlings, making evaluations easier since they are not
covered with other material (Fig. 5.5). Analysts can easily monitor development of all seedling parts except
roots which are imbedded in the creped cellulose paper. The AOSA rules provide three conditions for
creped cellulose paper: C = creped cellulose paper wadding covered by a single thickness of blotter through
which holes are punched for the seeds pressed for about one-half their thickness into the paper wadding,
TC = seeds placed directly on top of creped cellulose paper without a blotter, and TCS = on top of creped
cellulose paper, covered with ½ - ¾ in of sand without a blotter.
The only speciication for creped cellulose paper in the AOSA rules is that it must be 1.0 cm (0.3 in)
thick Kimpak or its equivalent. Because of its high water holding capacity (up to 16 times its dry weight),
extreme care must be used in measuring the amount of water added. A mechanical watering device (Fig.
5.6) can be useful in ensuring that the optimum amount of water is added. When blotters are used, they
serve to support and maintain seed spacing and permit more aeration by absorbing the excess water from
the creped cellulose paper. Unless excessive drying occurs during the germination period, it is usually not
necessary to rewater Kimpak.
