germination

Examples of germination in the following topics:

• Development of the Seed

  • This tissue becomes the food the young plant will consume until the roots have developed after germination.
  • Upon germination, enzymes are secreted by the aleurone, a single layer of cells just inside the seed coat that surrounds the endosperm and embryo.
  • Upon germination in dicot seeds, the epicotyl is shaped like a hook with the plumule pointing downwards; this plumule hook persists as long as germination proceeds in the dark.
  • As the seed germinates, the primary root emerges, protected by the root-tip covering: the coleorhiza.
  • Upon a return to optimal conditions, seed germination takes place.

• Fruit and Seed Dispersal

  • Seeds contained within fruits need to be dispersed far from the mother plant so that they may find favorable and less-competitive conditions in which to germinate and grow.
  • Coconuts are well known for their ability to float on water to reach land where they can germinate.
  • Some animals, such as squirrels, bury seed-containing fruits for later use; if the squirrel does not find its stash of fruit, and if conditions are favorable, the seeds germinate.
  • Dormant seeds can wait months, years, or even decades for the proper conditions for germination and propagation of the species.

• Abscisic Acid, Ethylene, and Nontraditional Hormones

  • ABA induces dormancy in seeds by blocking germination and promoting the synthesis of storage proteins.
  • Plants adapted to temperate climates require a long period of cold temperature before seeds germinate.
  • As the hormone gradually breaks down over winter, the seed is released from dormancy and germinates when conditions are favorable in spring.
  • Strigolactones promote seed germination in some species and inhibit lateral apical development in the absence of auxins.
  • Apical dominance, seed germination, gravitropism, and resistance to freezing are all positively influenced by hormones.

• Mosses

  • The most familiar structure is the haploid gametophyte, which germinates from a haploid spore and forms first a protonema: usually, a tangle of single-celled filaments that hug the ground.
  • The alternation of generations cycle begins when the gametophyte germinates from a haploid spore and forms a protonema.
  • Spores released from the sporophyte germinate and produce gametophytes; the process begins again.

• Double Fertilization in Plants

  • After pollen is deposited on the stigma, it must germinate and grow through the style to reach the ovule.
  • The germination of the pollen tube requires water, oxygen, and certain chemical signals.
  • Embryonic development is suspended after some time; growth resumes only when the seed germinates.

• Zygomycota: The Conjugated Fungi

  • When spores land on a suitable substrate, they germinate and produce a new mycelium.
  • When the zygospore germinates, it undergoes meiosis and produces haploid spores, which will, in turn, grow into a new organism.

• Plant Nutrition

  • First, seeds must germinate under the right conditions in the soil; therefore, temperature, moisture, and soil quality are important factors that play a role in germination and seedling development.

• Protist Life Cycles and Habitats

  • If this occurs, the spores germinate to form amoeboid or flagellate haploid cells that can combine with each other and produce a diploid zygotic slime mold to complete the life cycle.
  • As with plasmodial slime molds, the spores are disseminated and can germinate if they land in a moist environment.
  • The sporangium forms haploid spores through meiosis, after which the spores disseminate, germinate, and begin the life cycle anew.
  • In aggregate form, some individuals contribute to the formation of a stalk, on top of which sits a fruiting body full of spores that disseminate and germinate in the proper moist environment.

• The Phytochrome System and Red Light Response

  • For example, if lettuce seedlings germinated a centimeter under the soil surface, the seedling would exhaust its food resources and die before reaching the surface.
  • A seed will only germinate if exposed to light at the surface of the soil, causing Pr to be converted to Pfr, signaling the start of germination.
  • In the dark, phytochrome is in the inactive Pr form so the seed will not germinate.

• Inorganic Nutrients and Other Factors

  • A fire will probably kill most vegetation, so a seedling that germinates after a fire is more likely to receive ample sunlight than one that germinates under normal conditions.