Agriculture Reference
In-Depth Information
Purity workboards vary greatly in design and material. Figure 4.2 (left) shows a popular design with
wooden top and side arm rests. Others may be simple table tops arranged at suitable heights with adequate
working space (Fig. 4.2, right). Usually, light-colored, preferably white, blue or green nonglare art paper is
placed on the board and fastened at the corners with thumbtacks or transparent tape to provide a convenient
working surface. A paper scoop or pouring device is made by folding a 4 x 6 in index card along one side.
This scoop provides a convenient pouring device for moving seeds or individual purity components into
holding containers following separation. The card also serves as an excellent retainer when properly folded
to prevent seeds from falling off the front of the working board. To properly set up a purity workboard, two
pieces of art paper should be used. The bottom piece is placed even with the front of the board. The top
piece is placed 2.5-3.75 cm (1 to 1.5 in) from the front edge. The card scoop slips between the two pieces
of paper and has the support of the workboard when illed with seeds that have been examined. When this
scoop is folded (upwards) once, the seed can be easily retained in the desired area.
Workboard surfaces of nonglare or frosted glass may also be used, depending on speciic separations
and analyst preference. Plastic surfaces should be avoided because of their tendency to build up static
electricity, causing small chaff and seeds to stick together or jump around. A
diaphanoscope
(Fig. 4.3) is
an inspection station with an opaque glass or plastic surface positioned over a small opening providing a
light source from below. The light provides a view of the internal seed structure of seeds which are thin or
translucent enough to allow the light to shine through them.
Figure 4.3. Diaphanoscope. When light shines through seeds, it provides a view of the internal seed structures.
Seed Containers
It is essential that analysts have an assortment of small containers such as small petri dishes, watch glasses,
small glass vials or gelatin capsules for holding various separations from the purity test. Incidental seeds
may be placed into these containers according to species or may be grouped as weed seeds or other crop
seeds for subsequent identiication and weighing. Laboratories use different types of envelopes for holding
and storing various sample components.
