How the seeds sprout: all the information on seed germination, from theoretical explanations to practical techniques to germinate seeds in seedbeds or open ground.
How the seeds sprout, the ideal conditions
To favor germination it is advisable to moisten the soil just after sowing: the seed needs water to reactivate the metabolism. When the metabolism of the seed is reactivated, the growth of the new plant, ie the embryo, can take place; it is with the development of the embryo that iseeds sprout! The favorable conditions to allow seed germination are:
- moist soil
- adequate temperature (which varies from species to species)
- presence of oxygen in the soil. The substrate must ensure good air exchange, there must be no crusts, nor must it be flooded
- absence of toxic substances such as heavy metals, herbicides, methane, hydrogen sulphide ...
For practical instructions, we refer you to the articleHow to sow, now we will focus on the embryonic development of theseed.
How the seeds sprout
The structure of the seed
Generalizing we can say that iseedsthey consist of some external protective layers (integument), these layers enclose and protect the embryo together with reserve substances (provisions, nutrients that the plant will use in the first phase of development).
On the mother plant, following the fertilization of the flowers, the fruits that enclose the seeds are formed. The seeds originate precisely following the fertilization of the ovules contained in the flower; fertilization takes place by the pollen carried by wind or pollinating insects.
As the embryo grows, the seed swells and begins to accumulate the "reserve substances" mentioned above: sugars, fats, proteins ... once the embryo has grown and the accumulation of nutrients, the seed begins to dehydrate. This phase occurs when the seed is still in the fruit.
Once ripe, the seed is dry, that is, it has only 5-15% water. Simultaneously with the loss of water, a slowing down of the metabolism occurs: the seed enters the resting phase and thus manages to resist the most adverse conditions.
With thesowing,the embryo enclosed in the integument ceases its vegetative rest because it enters a context in which the ideal development conditions (those described above) occur. The presence of moisture allows the seed to re-hydrate and reactivate the metabolism that will give the embryo the strength to develop and form the firstreal leaves.The seedssproutthanks to the embryonic development that takes place only in favorable conditions and only if the seed has reserves. In the bean, for example, the reserves are entirely contained in the cotyledons, that is, the first two leaflets that will be emitted by the new plant. The first true leaves, which have different shapes and functions than cotyledons, are called "true leaves". In fact, the cotyledons are not leaves but in seeinggerminatea plant very often makes this mistake: the cotyledons are more oval.
The greater the reserves contained in the seed, the greater the chances for the plant to overcome adverse conditions (sudden changes in temperature, heavy rain…). In the early stages of growth, the plant depends entirely on the nutrient reserves contained in the seed but in a short time it becomes autonomous and begins to take nourishment from the soil thanks to the development of an effective root system and aerial vegetation.