Agriculture Reference
In-Depth Information
Cool Germination Test
The cool germination test (Figs. 8.10 and 8.11) was developed for testing the vigor of cotton seed lots, but
it has also been used for sorghum and cucumber seed. It is conducted at a temperature substantially below
that required for optimum germination. A major advantage of this test is that it is conducted and interpreted
using criteria similar to a standard germination test. Cool tests of cotton germinate seeds at 18°C which is
close to their minimum growth temperature of about 15°C. At the end of the test period, the percentage of
normal seedlings with a combined hypocotyl and root length of 4 cm is calculated and the value represents
a “vigor rating” for the seed lot. The
cool-warm germination index
is a modiication of the cool test. This
alternative test is actually a combination of two tests, the cool germination test and the standard germina-
tion test. In this version of the test, both the cool and warm germination are performed on samples from the
same seed lot. The two test results are then combined by adding the percent normal germination of each,
producing a single score called the cool-warm vigor index.
The cool test probably has potential for use over a wide range of species. However, it has not been
widely studied, probably due to the availability of other vigor tests. More details are described in the 2009
AOSA Vigor Testing Handbook.
Figure 8.10. Cool germination test on cotton. Only normal seedlings with a combined hypocotyl and root
length of 4 cm are counted.
Figure 8.11. Cool germination test of cotton. On the left, a seedling with combined hypocotyl and root length
greater than 4 cm. On the right, a seedling with combined hypocotyl and root less than 4 cm.
