Cucurbit Genetics Cooperative Report 4:13-16 (article 7) 1981
The Effects of Fermentation and Storage Time on Germination
of Cucumber Seeds at Optimal and Suboptimal Temperatures
James Nienhuis and R. L. Lower
University of Wisconsin,
Madison, WI 53706
One technique commonly used to clean cucumber seeds is
to scrape the placental tissue and seed from the seed cavity
and allow natural fermentation to occur for a given length
of time. At temperatures between 15 and 21°C sufficient
fermentation will usually occur within 3 to 6 days (1). However, the effect of the duration of fermentation on the
germinability of cucumber seeds is not well documented.
In tomatoes, Lower and Cadregari (4) found differences in
varietal response to the duration of fermentation. After
12 days of fermentation the percent germination in one variety
decreased from 95 to 20%, whereas in another variety germination
remained in excess of 90%.
An additional potential problem in seed germination is
that some or all seeds of several crop species are dormant
at harvest (3). In adapted Cucumis sativus cultivars
fresh seed dormancy, though seldom a serious problem, can
be overcome by removal of the seed coat, infusion of any
of several growth regulators, or dissipated during storage
(2, 5, 6, 7).
The objective of this study was to observe the effects
of the duration of fermentation and storage time on the
rate and percent germination of cucumber seed at optimal
(25°C) and suboptimal (15°C) temperatures.
Materials and Methods
Mature fruit were harvested from a random mated heterogenous
population of adapted cucumber lines which were field grown
at the Hancock Experiment Station, Hancock, WI. Seeds and
pulp were scraped from the seed cavity of more than 200
fruit and bulk fermented at 25°C. The fermenting material
was stirred daily and bulks of seed were sampled over a
12-day period. The seed samples were washed to float off
debris, dried on a screen overnight, and then placed in
storage. The storage room conditions were variable, and
the temperature ranged from 15 to 25°C; this simulated
normal storage conditions of seed used in our breeding program.
Germination was tested by removing samples of seed from
storage at specified intervals of time and placing 50 seeds
on filter paper in 90 mm petri dishes with 10 ml of water.
The treatment combination represented a 6x7x2 factorial
set, i.e. 6 fermentation times (0, 1, 2, 4, 8, and 12 days),
7 storage times (0, 1, 2, 4, 8, 20, and 30 weeks), and
2 germination temperatures (15 and 25°C). The experimental
design was randomized complete block with two replications
(petri dishes) per treatment. Germination readings were
taken at 3, 6, 9, and 12 days after planting. The percent
germination after 12 days and the germination rate (mean
number of days to germinate of those seed which germinated)
were calculated. Germination was defined as radicle emergence
of 5 mm or longer. For the analysis of variance arcsine
transformation was performed on percentage data. Significant
main effects were subjected to further analysis to fit the
appropriate regression model.
Main effects of fermentation. The pH of the fermenting
material increased from 4.0 at day 0 to 4.5 after eight
days of fermentation. The effect of fermentation duration
on the percent germination gave contrasting results at 15
and 25°C. The percent germination at 25°C remained
above 97% over the first four days of fermentation and then
decreased to 83% after 12 days of fermentation (Fig. 1).
The percent germination at 15°C varied about a mean
of 3% regardless of the duration of fermentation time (Fig. 1). The effect of fermentation duration on the germination
rate at 15 and 25°C was similar. The rate of germination
at 25°C was stable at three days over the first four
days of fermentation and then slowed to six days after 12
days of fermentation (Fig. 2). The rate of germination at
15°C slowed linearly from 7.5 days initially to 10 days
after 12 days of fermentation (Fig. 2).
Main effects of storage time. The seed was stored
from September 1980 to May 1981; during that time seed moisture
was reduced from 7.3 to 5.0%. The effect of the duration
of storage time on the percent and rate of germination gave
contrasting results at 15 and 25°C. The percent germination
at 25°C remained above 915 regardless of storage time
(Fig. 3). The percent germination at 15°C increased
from 1 to 18% after 30 weeks of storage (Fig. 3). The rate
of germination of 25°C accelerated from 4.1 days initially
to 3.2 days after eight weeks of storage, and then slowed
to 3.9 days after 30 weeks of storage (Fig. 4). The germination
rate at 15°C varied about mean of 8.9 days regardless
of storage time (Fig. 4).
Fermentation for up to four days at 25°C adequately
separated seeds from pulp for cleaning, without adversely
affecting the viability of cucumber seeds from this population.
However, excess fermentation beyond four days resulted in
reduced germination and a slower rate of germination at
an optimal temperature (25°C).
The initial accelerated rate of germination at 25°C
and the increased percent germination at 15°C with storage
time indicate continued physiological changes in cucumber
seeds during storage. Whether these changes simply reflect
a response to decreased seed moisture prior to imbibition
or dissipation of low temperature germination inhibitors
with age or some other phenomena remains to be tested.
The results of this study provide information useful in
understanding occasional erratic germination of cucumber
seeds which have been subjected to different processing
methods. In addition, the results focus attention on how
the effects of processing, handling, and storage of cucumber
seeds can alter their ability to germinate at both optimal
and suboptimal temperatures. These effects will warrant increased
attention in the planning and interpretation of future seed
- Hawthorne L. R. and L. H. Pollard. 1954. Cucurbitaceae.
pp. 206-207. In: Vegetable and Flower Seed Production.
Blakiston Co., Inc., New York.
- Heit, C., R. W. Robinson and W. Mishanec. 1978. Dormancy
of Cucumis species. Cucurbit Genetics Coop.
- Justice, O. L. and L. N. Bass. 1978. Seed Dormancy.
pp. 20-21. In: Principles and Practices of Seed Storage.
Ag. Handbook No. 506, USDA/ARS, Washington, D.C.
- Lower, R. L. and C. H. Cadregari. 1965. Effects of fermentation
on germination of tomato seed. Veg. Imp. Newsletter 7:12.
- Nelson, J. M. and G. C. Sharples. 1980. Effect of growth
regulators on germination of cucumber and other cucurbit
seed at suboptimal temperatures. HortScience 15:253-254.
- Shifriss, O. and W. L. George. 1965. Delayed germination
and flowering in cucumbers. Nature 208:424-425.
- Watts, V. M. 1938. Rest period for cucumber seeds.
Proc. Amer. Soc. Hort. Sci. 36:652-654.