Stratification (botany)
In botany and in seed cultivation, a treatment of seeds that is suitable for stimulating their germination in a buffered environment, for example by exposure to cold , is referred to as stratification (from the Latin stratum `` layer '') . Substrate layers, which physically stabilize the water content, the temperature and the exclusion of light and reduce the unavoidable infestation with microorganisms in free, moist storage, serve as buffers.
Almost all seeds go through a seed dormancy or dormancy during and immediately after their maturity on the mother plant , which must be overcome before germination can take place. This initially serves to prevent germination on the mother plant. In addition, certain environmental conditions must often be met so that the seeds can germinate. Many types of seeds require a cold period before dormancy is overcome. This prevents seeds from germinating in the inconvenient time before the onset of winter. If seeds are artificially exposed to these conditions, one speaks of stratification .
The term vernalization refers to the induction of the flowering process through a cold period. Like the stratification of plants, this can be done in the seed stage. For example, perennial plants need hibernation to form flowers.
Stratification in wood reproduction
Hard-shelled seeds of woody plants are pretreated through special storage conditions over several weeks or months so that they emerge at the same time in the seedbed, i.e. develop into a seedling. In late autumn, the kernels of peaches , cherries, plums , etc. are placed in a container (barrel, wooden tub) alternating with moist gravel in layers (about the height of the kernel). They are stored in a cool but frost-free place for several months until the end of winter. During this time the hard shell swells and opens. At the same time the seed gets into a germination mood. In March / April the kernels, which have been pretreated by stratification, are placed in a suitably prepared seed bed.
Stratification in vegetable growing
If cold germs are sown, they need a cold period to germinate. Seeds sown in autumn naturally only germinate after winter when the snow melts in spring. Before sowing in warm spring, the seeds of a cold sprout are therefore stratified by placing them in a refrigerator or even in a freezer compartment (also depending on the species) for a certain period of time (depending on the species). This method can also be used to germinate seeds that have been wintered warm in the house.
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The following standard works deal comprehensively with the topic of stratification for all trees and shrubs propagated in Central Europe:
- Andreas Bärtels: Wood multiplication , Ulmer: Stuttgart. ISBN 3-8001-5186-3
- Donnchadh MacCarthaigh (Hrsg.), Wolfgang Spethmann (Hrsg.): Krüssmanns Gehölzvermehrung , Ulmer: Stuttgart, 2003 (until 2003 Paul Parey Buchverlag). ISBN 3-8001-4547-2
Older works explain the origin of the term stratification (stratification of seeds) from forestry practice particularly well (example):
- Hubert Rupf: Der Forstpflanzgarten , Bayerischer Landwirtschaftsverlag: Munich 1952 (without ISBN)
An example of today's stratification process:
- Andreas Ludwig, Bavarian State Institute for Forests and Forestry: Stratification of red beech seeds (PDF file; 109 kB)
The (university) biology demonstrates to its freshmen the breaking of dormancy with the biotechnical process of stratification . However, there is no research into the underlying biochemistry:
Individual evidence
- ↑ DuMont's large garden encyclopedia , DuMont, Cologne 1994, ISBN 3-7701-4605-0 (translation of Encyclopedia of Gardening , Dorling Kindersley, London 1992), p. 589.