- Germinating seeds often encounter stress conditions
of temperature, moisture and oxygen in the field.
Germination tests conducted under these stress conditions
in the laboratory might be methods of differentiating high
and low vigor seeds.
The objectives of this study were to (1) determine
if these stress conditions reduce germination performance
of low vigor seeds more than high vigor seeds, and
(2) determine the potential for using one or more of
these stress environmental conditions as the basis of a
vigor test to predict relative field performance of wheat
Seed lots of varying levels of deterioration were
produced by artificial aging of 'Malcolm' wheat (Triticum
aestivum L.). Germination tests were conducted at
temperatures of 5, 10, 15, 20, 25, and 30°C; water
potentials of 0, -0.2, -0.4, -0.6, -0.8, -1.0, -1.2, and
-1.4 MPa; and oxygen levels of 2, 4, 8, 12, 16% and air (21%). The water and oxygen stresses were applied at
six temperatures. Laboratory germination results were
compared to field emergence percentages of artificially
and naturally aged seed lots.
Germination percentage and rate of germination of low
vigor seeds were depressed more than that of high vigor
seeds at all water potentials and temperatures. At 20°C,
for example, germination percentage of high, medium and
low vigor seed lots at -0.6 MPa were 76, 48 and 29%
respectively, compared to nearly 100% at 0, -0.2 and -0.4
MPa. Similar relationships existed at the other
Germination of low vigor seed generally declined with
each reduction of oxygen level while that of high vigor
seed remained nearly constant. The germination
differential between high and low vigor seed lots widened
to as much as 30% in 2% oxygen at 30°C.
Twenty-four naturally-aged seed lots representing six
varieties and four production years were evaluated for
germination under water stress and field emergence.
Correlation coefficients between germination at -0.6 MPa
and field emergence were 0.61** and 0.59** for untreated
and Arasan-treated seeds, respectively.
It is clear from these studies that environmental
stresses reduce the germination of low vigor seeds more
than that of high vigor seeds. A vigor test based on one or more of these stresses has potential for being a
practical and realistic method of predicting the relative
field performance of wheat seed lots.