Agriculture Reference
In-Depth Information
number of important functions. First, it enables the number of normal seedlings germinating rapidly to be
recorded, and can provide an index of seed lot quality. Second, the seedlings classiied as germinable can
be removed, thus conserving substratum moisture and reducing crowding of rapidly growing seedlings.
Third, the irst count allows the analyst to evaluate the moisture status of the substratum and make neces-
sary adjustments. Finally, the disease status of the seedlings can be evaluated, permitting infected seedlings
to be removed to avoid secondary infection of nondiseased seeds. Germination tests generally should not
be completed early because contracts are usually based on the percentage germination of a seed lot. Thus,
a test concluded early might adversely affect payments to the grower. However, there are two times that a
germination test can be concluded early. The irst is when all the ungerminated seeds are found to be dead.
The second is when the report reads “Preliminary germination results at (X) days, inal report to follow.”
The inal count is the time when the germination test is terminated. It is the time when all seeds
have had suficient time to express their germination potential. The inal count period does not include
prechill recommendations speciied in the AOSA and ISTA rules. Thus, Kentucky bluegrass seeds which
require a 21 day inal count and 5 day prechill at 10°C would require a total of 26 days. However, the inal
count period can be modiied. If the analyst is certain that maximum germination has been attained, the
test can be terminated prior to the speciied inal count. However, if the seedlings are insuficiently devel-
oped for classiication, the inal count period can be extended an additional one to three days. For species
of Convolvulaceae, Geraniaceae, Malvaceae, and Fabaceae, which often possess hard seeds, all seeds or
seedlings can be removed except those that are swollen or just starting to germinate. These can be left
an additional 5 days beyond the inal count and any normal seedlings developing after this period can be
added to the inal germination count. Many inal count recommendations occur at 7-day intervals which are
purposely designed so the inal count may occur on a work day (based on the calendar 5-day work week).
When inal count results are low, reason(s) for the low germination should be noted.
Between the irst and inal counts, intermediate counts can also be employed. These are often used
when disease or some other factor that potentially inluences germination needs to be monitored carefully.
Intermediate counts have a place in providing the analyst additional information concerning the germina-
tion capability of the seed lot that irst and inal counts do not supply.
EVALuATIon of SEEdLInGS
At the inal count , seedlings are evaluated as to whether they are normal or abnormal. According to AOSA,
normal seedlings are deined as “seedlings possessing the essential structures that are indicative of their
ability to produce normal plants under favorable conditions.” Abnormal seedlings are deined as “all
seedlings that cannot be classiied as normal.” Only normal seedlings are considered germinable. Normal
seedlings have a well-balanced symmetrical growth pattern of all essential parts. The presence of broken,
stunted or weakened and malformed seedlings should alert the analyst to suspect seedling abnormality. It is
very important that all seedlings be allowed to develop to a stage where it can be determined if all essential
parts are present at the inal count. In order to complete the germination analysis at the inal count, the ana-
lyst must evaluate the remaining ungerminated seeds and determine whether they should be considered as
(a) dead, (b) dormant, or (c) hard.
Seedling descriptions
The classiication of normal and abnormal seedlings is one of the more subjective aspects of seed testing
and requires constant training and experience to assure uniformity of interpretations. Criteria for normal
seedlings are set forth and illustrated in the AOSA and ISTA seedling evaluation handbooks.
 
Search WWH ::




Custom Search