Seed storage and longevity
Seeds, even if adequately protected during storage, still
undergo deterioration with time. Major factors affecting longevity (Iife-span)
of mature, viable and healthy seeds are moisture, storage temperature and pests.
Most seeds are drying-tolerant (orthodox). Under ordinary room
conditions (open storage), viability of these seeds is generally reduced by half
within six months. Seeds with harder seed coats tend to live longer than those
with thin coats. For improved storability, seed moisture and storage temperature
must be kept low and controlled.
1. Store only new, mature, healthy and well-dried seeds, except
for a few species which do not favor drying. Keep these in dry and cool
environments for longer viability.
2. Seeds easily reabsorb moisture. To maintain dryness, place
dried seeds in air-tight containers like tin cans or glass jars with
tight-fitting lids and use some water-absorbing materials like sifted dry wood
ash (white), dry charcoal, toasted rice (cooled), silica gel or pieces of
newspaper (to occupy about a fourth of the container). Place a sheet of paper on
top of these water absorbing materials if seeds are to be put directly into the
container. Replace or redry these materials if containers are frequently opened.
Fill the rest of the container with seeds. Plastic bags may be used to keep
seeds dry if sealed by heat.
3. Label containers with the harvest and storage dates and place
of harvest (or acquisition). If possible, also indicate the initial percentage
viability or germination of seeds.
Picture 13
4. Dry seeds may be protected from insects by using naphthalene
bails (1 or 2 pieces per kg seed) or by mixing seeds in the containers with some
materials like fine sand, dry wood ash, powdered seeds of black pepper or neem,
plant oils from coconut, neem, peanut, castor, cotton, etc., (one teaspoon of
oil per kg seed).
A few species have seeds which are sensitive to drying and,
often, also to cold temperature (recalcitrant). They have storabilities of only
several days to a few months under ordinary room conditions in contrast to the
drying tolerant or orthodox species. Recalcitrant characteristics are commonly
found in many fruit, plantation and forest species (such as lanzones, rambutan,
durian, mangosteen, mango, jackfruit, avocado, rubber, cacao and Dipterocarpus
spp.)
Picture 14
For slightly longer storabilities, keep these seeds wellcleaned
and moist (1 to 2 days of air-drying is generally sufficient to keep the seed
coat slightly dry but still moist inside). Store them in small batches in a cool
room in inflated plastic bags (half-filled with seeds and opened once a day to
prevent fermentation) or in perforated plastic bags. Moist charcoal, peat moss,
sawdust, sand or coirdust may also be placed inside the bags. Moist storage for
more than a week requires that seeds be protected from molds and bacteria. This
may mean soaking seeds in a sterilant like the commercial bleach, chlorox (1
part chemical to 5 parts water) or applying anti-mold substances like fungicides
or some plant extracts (try extracts of garlic cloves, acapulco leaves,
malunggay leaves or achuete seeds). A temperature of 15 C is often used to
further prolong storabilities and, to some extent, reduce infection.
Recalcitrant seeds also need special attention during transport. The life time
of seeds can be extended if extraction is deferred until seeds arrive at the
collection site at which time care must be taken to avoid heating and/or
fermentation of fruits by aeration or
cooling.
