Agriculture Reference
In-Depth Information
Speed of Germination and Seedling Growth rate
Anyone who has planted a garden has noted that some seeds (seedlings) emerge faster than others. Thus, the
speed of germination test is one of the oldest, most credible tests for seed vigor. However, it has not been
widely used by the seed industry, and very few laboratories employ this method as a practical test for seed
vigor (Table 8.4).
Several methods for determining speed of germination and seedling growth can be used in evaluating
seed vigor. The vigor of different seed lots can be compared by the number of days required to reach 90%
(or 50%) of the inal germination. The irst count of germination speciied in the Rules for Seed Testing can
be used as an index of speed of germination. This may be further indexed by use of one of the following
formulae that have been proposed for this purpose:
1. Speed of Germination Index
. This formula, developed by Maguire (1962), is probably the most
commonly used speed of germination formula. The speed of germination index is calculated as:
SGI=
No.normalseedlings
daysof firstcount
+
No.normalseedlings
daysofsecondcount
+ ............... +
No.normalseedlings
daysof finalcount
Speed of germination index is the sum of quotients of number of normal seedlings per each repli-
cation used in the germination test (e.g., 100 seeds) obtained at each counting date in the standard
germination test.
2. Germination Value
. This index was developed by Djavanshir and Pourbeik (1976) for use on tree
seeds, and combines speed and completeness of germination as:
GV=
!DGS
N
(GPx10)
where DGS is daily germination speed, computed by dividing cumulative germination percent
by the number of days from beginning of the test, N is frequency of number of DGS and GP is
germination percent at the end of the test.
3. Mean Germination Time
. The use of mean germination time (MGT) was proposed by Ellis and
Roberts (1980) as an indication of vigor. It is calculated as:
MGT
=
i
N
i
T
!N
i
where N
i
is the number of seedlings present on day
i
, T
i
is the
i
th day since the beginning of the
test, and ΣN
i
is the inal germination.
The speed of seedling growth is closely associated with the speed of germination as described above.
However, the measurement of seedling growth may be easily incorporated into germination growth rate
tests by imposing a standard criterion (e.g., length) before seedlings are considered to have germinated.
A modiication of this procedure can be to measure the dry weight of the growing part of the germinating
seedling during a given time after planting. The results may be based on the weight of a given number of
seedlings, or the mean weight per seedling. If this test is accurately and precisely done, it should provide an
excellent measure of comparative vigor among different seed lots. For more details, refer to the 2009 AOSA
Seed Vigor Testing handbook.
Computer applications.
Seedling growth rate determinations are ideal models for computer-assisted
technology because of the needs for periodicity and objectivity in evaluation. For example, image analysis
techniques have been developed for lettuce and carrot (McCormac et al., 1990) and lettuce and sorghum
