Germination

Sunflower seedling, three days after germination

Germination occurs when a spore or seed starts to grow. It is a term used in botany. When a spore or seed germinates, it produces a shoot or seedling, or (in the case of fungi) a hypha. The biology of spores is different from seeds.

A spore germinates if and when conditions are right. It has a very limited lifespan. The method of spore-bearers, which are lower plants such as mosses, ferns and also fungi, is to produce vast numbers of spores, of which only a small percentage germinate.

Seeds contain an embryo, a store of food (the endosperm), and a protective coat. Seed plants include Gymnosperms (such as conifers) and Angiosperms (such as flowering plants). Seeds can survive much longer than spores, sometimes for hundreds of years. The strategy of seed-bearing plants is to invest energy and material in the substance of seeds, and they have evolved more sophisticated methods of dispersal than just wind.^[1]^p98

Seeds do not germinate until their requirements are met, and these needs differ from species to species.^[2]

The dormancy period must be over. Dormancy is governed by changes inside the seed. Each species has its own dormancy period, and will not germinate until that period is over.
Their hibernation must be over. The hibernation is ended when events in the environment trigger germination. Sometimes this is just temperature and water, sometimes fire, sometimes the seed must go through a long cold spell.

The requirements for fruits is the same as for seeds. A fruit is just a seed with one or more extra layers derived from parts of the flower.

Germination Media

Sunflower time lapse with soil. Cross section, showing how the root and the upper part of the plant grow
A seed pot used in horticulture for sowing and taking plant cuttings and growing plugs
Germination glass (glass sprouter jar) with a plastic sieve-lid
Brassica campestris germinating seeds
Time-lapse video of mung bean seeds germinating
Malted (germinated) barley grains
Germination of seedlings raised from seeds of eucalyptus after three days of sowing
The stages of germination of a pea plant: A. seed coat, B. radicle, C. primary root, D. secondary root, E. cotyledon, F. plumule, G. leaf, H. tap root

References

↑ Fenner, Michael and Thompson, Ken 2005. The ecology of seeds. Cambridge. ISBN 978-0-521-65368-8
↑ Baskin C.C. & Baskin J.M. 1998. Seeds: ecology, biogeography, and evolution of dormancy and germination. Academic Press, San Diego.

[Fenner-1] Fenner, Michael and Thompson, Ken 2005. The ecology of seeds. Cambridge. ISBN 978-0-521-65368-8

[Baskin.2C_C.C_1998-2] Baskin C.C. & Baskin J.M. 1998. Seeds: ecology, biogeography, and evolution of dormancy and germination. Academic Press, San Diego.

[1]

[2]