E. Other Treatments
The pelleting of seeds has been used for a long time with varied success. Although there are different ways
of pelletizing seeds, in the simplest procedure, seeds are placed in a rotating drum and coated with a liq-
uid binder and dust. The procedure results in uniform-sized, spherical pellets that facilitate more precise
planting and often increased and more uniform germination [2,61].
Grass, vegetable, and flower seeds and sometimes seeds of woody species have been “seeded” in
plastic rolls, tapes, or in water-absorbent, fibrous mats. The seeds are held in position by water-soluble
adhesives [61]. These procedures simplify planting and may result in more uniform germination and
seedling establishment. The roll, tape, or mat serves as a mulch and provides a more uniform germinat-
ing environment. Often fertilizers, inoculants, insecticides, fungicides, and other chemicals are added to
improve the effectiveness of these products [2].
VIII. COLLECTION AND STORAGE
Seed companies and seed banks regularly conduct germination tests in controlled laboratory conditions
to determine the relative viability of seed lots and to maintain quality control. These tests also determine
the temperature and moisture limits for successful storage of each type of seed [8,24].
Each type of seed must be collected, handled, and stored differently. In theory, seeds are ready to har-
vest when there is no further increase in weight. Seeds from different species mature at different times of
the year [39]. Some seeds that appear ripe may in fact contain undeveloped embryos. Fruits have many
different shapes and sizes and may be fleshy or dry, dehiscent or indehiscent. The fleshy coverings of
some fruit may contain substances that inhibit germination and must be removed. Removing such cover-
ings lessens the chance for bacterial or fungal growth, which may effect seed viability. Freshly harvested
seeds of some species may require no treatment, or less stratification time, compared with those that have
been dried and/or stored. The seed coat of Crataegusspp. (hawthorns), although not impermeable when
freshly collected, becomes so after drying (Table 3).
Under normal conditions, many seeds are relatively short lived or lose viability with time. Hellum
[62] reported a 12% reduction in the rate of germination of Pinus balsamiferaseeds stored at 7°C for 4
months. Seeds of Acer saccharinum(silver maple) remain viable for only a few days if they are not kept
moist and cool (Table 3). Salix(willow) and Populus(poplar or aspen) seeds are viable for only 4 weeks,
but many other seeds remain viable for several to 15 years and some longer. Because many woody species
do not produce seed abundantly each year, commercial seed companies must collect and store seeds of
these species for many years. Therefore, many different methods of collecting, handling, and storage are
required. These methods have been described by other authors [2,8,34,39,63].
Under proper storage conditions, seeds of most species can be kept viable for 5-year periods. Keep-
ing them dry, usually 5–12% moisture content, and keeping them cool are the most important factors af-
fecting longevity and viability. A temperature range of 0–5°C is usually adequate for most species, al-
though lower temperatures may be acceptable for some. Freeze-drying at temperatures below 1°C with
moisture control appears to offer the best storage conditions [12] but is not an economical way to store
most seeds.
IX. SUMMARY AND CONCLUSION
The geographic location or provenance of a seed can substantially influence its germinability. Seeds col-
lected from different geographic sources may not germinate or perform uniformly under the same condi-
tions. Those from a more southerly location may require a shorter stratification period to overcome dor-
mancy and may result in plants that are less winter hardy in a more northerly location. Because of
preharvest environmental conditions that affect seed maturation or seed-handling procedures and humid-
ity and temperature of storage, which affect the permeability of the seed coat, seed treatments may yield
different results between seed lots of the same species or from year to year. Therefore, treatments and other
requirements (Tables 2 and 3) should be considered as guides and may need to be modified to compensate
for variations in seed condition. Differences in germination requirements have evolved in response to
species adaptation to changing environments or to selection pressure by cultivation and breeding.
GERMINATION AND EMERGENCE 113