People working in the agricultural industry will often carry out processes that imitate these natural ones in order to break dormancy and get seeds to germinate—for instance, by chilling seeds to imitate cold weather or by applying abrasives to weaken the seed coat. How long can a seed survive? Most seeds seem to be able to live in the soil for between 10 to 15 years.
But the lifespans of seeds vary enormously. The seeds of some annual grasses need to germinate within a few weeks, while those of other plants may slumber for hundreds of years. The Arctic lupin holds the record so far. Seeds of this plant were found in the burrows of lemmings in Alaska. Researchers were able to germinate the seeds—which had been buried in the Arctic soil since the end of the last Ice Age—and produce plants. Some Australian plants need to be exposed to the heat of fire for the germination process to begin.
A short burst of heat from a bush fire is thought to crack the hard seed coat of native peas and acacias wattles. In contrast to those plants that release their seeds spontaneously when they reach maturity, fire is also needed for some species to release their seeds from woody fruits. These plants rely on an environmental cue—in this case, fire—to know when to drop their seeds.
They include species of hakea, banksia and eucalypts. Banksias, for example, can keep their seed for years in a woody fruit called a follicle. During a fire, the parent plant may be killed but the fruit will open up. The ready-to-germinate seeds fall to ground, which, thanks to the bushfire, has been cleared of competitors and nicely fertilised with ash.
Researchers have long known that many species of Australian plants germinate after a fire. Indeed, many of us in Australia will have observed decimated and blackened bushland, which, shortly after, amazingly transforms into a riot of green, with new shoots popping up everywhere. So what was it about bushfires that helped them germinate? The molecule, which they named karrikinolide after the Nyungar word, karrik, which means smoke is in a class of molecules called butenolides.
These are a byproduct of the combustion of cellulose together with other organic compounds in plant tissues. By dissolving the compound in water, the researchers were able to get many dormant Western Australian seeds, as well as species from around the world, to germinate rapidly. They also discovered many other species for which karrikinolide improves germination, such as lettuce, celery and others.
But did you know that many plants also rely on insects and animals to transform from a seed to a seedling? Animals help seeds by carrying them to a place where they can germinate.
This may be as simple as a bird knocking seeds to the ground while landing on a branch. Perhaps more significantly, by eating the seeds often attracted by the ripened fruit surrounding them , birds, bats, insects and other animals may carry them away from the parent plant in their gut, to be deposited somewhere else—in their poo. Why is this dispersal an advantage for seeds? This final step before seedlings are planted in the field gradually exposes them to the conditions they will have in the field.
This process stimulates the plants to accumulate carbohydrate and nutrient reserves and strong cell walls by exposing the plants to day and night temperature fluctuations, increased air movement and wind, reduced watering, and full light.
Hardening off transplants is important, especially if they are to be planted under stressful early season conditions. Most transplants may be hardened off by reducing the temperature in the greenhouse through ventilation.
Reduced watering will also provide some hardening effect. Do not let plants wilt excessively. Do not harden off transplants by reducing fertilizer application, as this often results in stunted plants that do not establish well in the field.
Some growers will put plants outside for days prior to planting. This allows the plant to become acclimated to outside conditions while still in the flat. Plants hardened off in this manner often have improved field performance as compared to those planted directly from the greenhouse Garton, Sikkema, Tomecek The National Organic Standards require that producers use organically grown seeds, annual seedlings, and planting stock.
Nonorganically produced, untreated seeds and planting stock may be used to produce an organic crop when an equivalent organically produced variety is not commercially available.
There is no allowance for seed treated with prohibited materials. Captan, thimet, and similar chemical fungicides are not on the national list and are not permitted.
Please take this seriously. If your seed is covered in a pink or orange powder, it is probably prohibited. We may not be able to certify your crop if you use seed treated with prohibited materials. The first step is to determine whether an equivalent organically produced variety is available. By equivalent variety, look for comparable growing habits, days to maturity, insect and disease resistance, flavor, and other important qualities. If a suitable organic equivalent variety is not available, document where you tried to look for organic seed, as that is important for your certification records.
Once you have found a source for a specific equivalent organic seed, the next step in determining commercial availability is to see if it is of the appropriate form, quality, and quantity. Compliance is reviewed in the context of the organic system plan, which is verified during the annual inspection.
A pattern of inadequate documentation and lack of good faith effort to obtain organically grown seeds and planting stock may be considered noncompliance and might result in Pennsylvania Certified Organic requiring prior approval regarding commercial availability issues in future planting cycles.
Listed below are a number of sources for organic seed provided by Pennsylvania Certified Organic For a more complete listing including forage, field crop, and cover crop seed and transplants, go to the Pennsylvania Certified Organic website. Fred C. Gloeckner and Co. Gardens Alive! Garton, R. Sikkema, and E. Kemble, J. Alabama Cooperative Extension, Mackean, D. Maynard, D. Knott's Handbook for Vegetable Growers. Hoboken, N.
Miles, A. Pennsylvania Certified Organic. Pennsylvania Heirloom Seed Savers Club. Raven, P. Ray, and S. Biology of Plants. New York: W. Freeman, The Incredible, Edible Seed. Why are seeds of different sizes and shapes? What are seeds made of — and how can they grow into fruitful plants?! Protecting seeds: The what, why, and how of seed treatments.
We work at universities, government research facilities, and private businesses across the United States and the world.
Categories: Climate change , Crop breeding , Food security , Home gardens. Enter your email address to subscribe to this blog and receive notifications of new posts by email. Email Address. Menu Home About Contact. Climate change What are the factors that determine seed germination? Planting a seed, tending to plants, and yielding some home-grown vegetables is quite satisfying. But, what goes into seed germination? Variables like temperature, moisture and oxygen are important. The root, or radicle, is the first plant part to emerge from a germinating seed.
Credit: Kevin Hudson. The soybean plants on the left germinated at more than double the rate than the seeds on the right.
Soaking or scratching the seeds will help break down the seed coat. Morning glories and locust seeds are examples. Other seeds need to be exposed to proper temperatures. Apple seeds will not germinate unless they are held at cold temperatures for a period of time.
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