Agriculture Reference
In-Depth Information
sedge (Cyperaceae), and sunlower (Asteraceae). For species with small embryos, it may be very dificult to
determine if the embryo is actually present; the analyst should have a good knowledge of seed morphology
in order to avoid misclassiications. For example, in Cyperus the embryo is very small and is attached at the
base of the seed (achene) and can be easily overlooked. Each seed of weedy plants from any of the families
named above must be dissected to determine if it contains an embryo. Cockleburs found in the sample must
be dissected to determine if seeds are actually present inside the burs.
Wild Onion and Wild Garlic produce aerial bulblets which are vegetative reproductive organs and fre-
quently occur as contamination in crop seed lots. All bulbs which have any part of the husk remaining and
are not damaged at the basal end are considered weed seeds, regardless of size. Bulblets which show obvi-
ous damage to the basal end, whether husk is present or not, are considered inert matter as well as bulblets
completely devoid of the husk and that pass through a 1/13th-inch round-hole sieve.
Dodder seeds are frequently found as incidental contamination in alfalfa and clover seed lots. Since dodder
plants in the ield contain lowers and seeds in various stages of development, the seeds are likely to be
found in all stages of maturity, ranging from those completely devoid of embryo to those with full embryo
development. Those which are completely devoid of embryos and seeds which are ashy gray to creamy
white in color are classiied as inert matter. Questionable seeds such as those that are normal colored but are
slightly swollen, dimpled, or have minute holes should be sectioned to determine if an embryo is present.
Where samples contain many dodder seeds which are questionable, the questionable group should be lined
up on the working surface according to color and dissected, beginning with the seed least likely to contain
an embryo.
Buckhorn. Black seeds of buckhorn plantain ( Plantago lanceolata ) without any brown color evident are
considered inert matter whether they are shriveled or plump. If there is any question about the presence of
brown coloration present, they should be examined under a 10-power binocular microscope and relected
luorescent light or daylight.
Naked Ragweed Seed. Ragweed seeds with both the pericarp and involucre missing are considered as
inert matter. Otherwise they must be classiied as weed seeds. The analyst must be positive that the naked
seeds (embryos) in question come from ragweed and not from some other member of the Asteraceae before
making the decision.
Seeds of Juncus spp. Individual seeds of Juncus spp. and seed-like structures are removed from the fruiting
structure and considered as weed seed. The fruiting structure itself is placed with inert matter.
Other Nonseed Particles Other nonseed particles such as nematode galls, visibly smutted kernels, ergot
sclerotia, soil or sand particles, shells, stones, sticks, stems, chaff, pieces of lowers, cone scales, and pieces
of bark are considered inert matter.
SPECIAL PurITy TESTS And ProCEdurES
Varietal Identification
Whenever possible it is important to determine the varietal purity of the pure seed component. For example,
a sample of soybean seed may contain 99% pure seed consisting of a mixture of two or more varieties.
Varietal tests are particularly important to seed certiication programs which require high levels of varietal
purity for certiied seed. They are also very important for providing labeling information as well as law
enforcement tests for checking the accuracy of seed lots labeled as to variety.
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