Agriculture Reference
In-Depth Information
before categorizing it as crop seed. The quick method has been used successfully for many years and pro-
motes uniformity and simplicity in purity testing results.
Other species such as legumes usually break along the cleavage separating the two cotyledons. For
these types of broken seed, the half-seed rule does not apply. Separated cotyledons, regardless of whether
the root-shoot axis or more than one-half the seed coat remains attached are classiied as inert matter.
Immature and Shriveled Seeds
Nongrass kinds.
Immature and shriveled seeds of nongrass kinds are considered pure seed rather than inert
matter, even though they are cracked or otherwise damaged, except for those of legumes, crucifers and
conifers with the seed coats entirely removed.
Grasses
. Immature seeds of grasses containing the caryopsis enclosed by the lemma and palea are consid-
ered pure seed rather than inert matter if some degree of endosperm development (e.g., one-third) (Fig. 4.9)
can be detected by viewing over light or by applying gentle pressure on the lemma and/or palea. Several
exceptions to this rule exist for particular species in which a caryopsis may not be required in the pure seed
unit or for species to which special testing procedures are applied (refer to the AOSA rules).
Fig. 4.9. According to the AOSA and ISTA rules, only those lorets that contain a caryopsis with at least 1/3
the length of the palea measured from the base of the rachilla are considered pure seed units in tall fescue and
other grass species (courtesy of Deborah Meyer, California Dept. of Food and Agriculture, Seed Laboratory).
filled vs. unfilled Seeds
In several families it is dificult or impossible to determine whether embryo development has occurred due
to the presence of a hard seed coat or fruit structure without destroying or disrupting the natural “seed” unit.
Such is the case for seed units in the cucurbit (Cucurbitaceae) and nightshade (Solanaceae) families as well
as those in the sunlower (Asteraceae), mint (Lamiaceae), buckwheat (Polygonaceae), carrot (Apiaceae),
valerian (Valerianaceae), and other families in which the “seed unit” is a dry, indehiscent, one-seeded fruit
(e.g., an achene).
