Agriculture Reference
In-Depth Information
testing laboratory in Tharandt, Germany. These pioneering efforts quickly led to the founding in 1876 of
the irst seed testing laboratory in the United States in Connecticut by E. H. Jenkins and publication of the
irst “Rules for Testing Seeds” in 1917.
development of the Standard Germination Test
These historic milestones illustrate that seed testing is important and has become a routine component of
determining the value of seed for over the last 150 years. Of prime importance, of course, has been the
assessment of a seed's ability to germinate and produce a normal seedling (see Chapter 5). This is because
successful and rapid stand establishment is often correlated with increased yields and added value of the
harvested product. This stand establishment ability has traditionally been monitored by the standard germi-
nation test. Thus, the AOSA deines seed germination as “the emergence and development from the seed
embryo of those
essential
structures
that, for the kinds of seed in question are indicative of the ability to
produce a normal plant under favorable conditions.” Yet, this deinition of seed germination and the purpose
of the test do not always provide the purchaser the correct information about a seed lot's stand
performance potential. The AOSA deinition of seed germination emphasizes that the seed analyst must
focus on
essential structures
which lead to the production of a normal plant. But, this emphasis on seedling
morphology often has little relationship with speed of growth, a prime aspect of the potential for successful
ield establishment. There are, in fact, a number of deiciencies in standard germination test philosophy as
it is conducted today. These include:
1. Methodology for the conduct of a standard germination test is standardized so that test results
are reproducible within and among seed testing laboratories. This process means that favorable
conditions are utilized as described in the AOSA deinition in order that greater uniformity in test
results is obtained. Tests must be conducted on artiicial, standardized, essentially sterile media in
humidiied, temperature controlled chambers. These conditions are so synthetic that they seldom
relate to ield conditions that seeds likely encounter. Because the standard germination test is
conducted under favorable conditions, it basically establishes the
maximum
plant producing abil-
ity of the seed lot. When ield conditions are optimum, the standard germination test values may
correctly identify ield performance of the seed lot. For the most part, however, test values over-
estimate actual ield emergence. We know, for example, that when the standard germination result
is 80%, we might obtain 80% emergence in the ield under rare circumstances. In most instances,
the ield emergence is considerably less.
2. The standard germination test is designed to provide a irst and inal count. The irst count has
a purpose of removing most of the “strong” seedlings that have already germinated. The inal
count is designed to provide a suficiently long period that even “weak” seeds are coaxed or
provided every opportunity to be considered germinable. The germination percentage, therefore,
is the sum of “strong” and “weak” seedlings. The dificulty with such a process is that “weak”
seedlings seldom perform adequately when provided environmental stresses associated with ield
emergence.
3. By deinition, germination is scaleless. A seed is considered either germinable or it is not. There
are no distinctions provided for “strong” or “weak” seedlings. Those considered germinable may
vary from weak to robust in ield performance. This inability to document the quality of the seed
fails to take into account the progressive nature of seed deterioration which has a major impact on
stand establishment.
4. The AOSA deinition of seed germination emphasizes that the seed analyst must focus on essential
structures which lead to the production of a normal plant. But this emphasis on seedling morphol-
ogy often has little relationship with rapidity of growth, a prime criterion of the potential for
successful ield establishment.
