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Fragmentation (reproduction)

Fragmentation or Clonal Fragmentation is a form of asexual reproduction or cloning where an organism is split into fragments. The splitting may or may not be intentional. Each of these fragments develop into mature, fully grown individuals that are a clone of the original organism. If the organism is split any further the process is repeated. Fragmentation is caused by mitosis. Meiosis is not involved in fragmentation.

Fragmentation is seen in many organisms such as molds, some annelid worms, and sea stars. Binary fission of single-celled organisms such bacteria, protozoa and many algae is a type of fragmentation.

Molds, yeast, and mushrooms, all of which are part of the Fungi kingdom, produce tiny filaments called hyphae. These hyphae obtain food and nutrients from the body of other organisms to grow and fertilize. Then a piece of hyphae breaks off and grows into a new individual and the cycle continues.

Fragmentation is observed in nonvascular plants as well, liverworts and mosses.

Contents

[edit] Plants

Fragmentation is a very common type of vegetative reproduction in plants. Many trees, shrubs, nonwoody perennials, and ferns form clonal colonies by producing new rooted shoots, which increases the diameter of the colony. If a rooted shoot becomes detached from the colony,then fragmentation has occurred. There are several other mechanisms of natural fragmentation in plants.

  • A few plants produce adventitious plantlets on their leaves, which drop off and form independent plants, e.g. Tolmiea menziesii and Kalanchoe daigremontiana.
  • Some woody plants naturally shed twigs, termed cladoptosis, e.g. willow. The twigs may form roots in a suitable environment to establish a new plant.
  • River currents often tear off branch fragments from certain cottonwood species growing on riverbanks. Fragments reaching suitable environments can root and establish new plants.[1]
  • Small pieces of moss "stems" or "leaves" are often scattered by wind, water or animals. If a moss fragment reaches a suitable environment, it can establish a new plant. [2]
  • Some cacti and other plants have jointed stems. When a stem segment, called a pad, falls off, it can root and form a new plant.
  • Leaves of some plants readily root when they fall off, e.g. Sedum and Echeveria.

People use fragmentation to artificially propagate many plants via division, layering, cuttings, grafting, micropropagation and storage organs, such as bulbs, corms, tubers and rhizomes. Sponges also reproduce by fragmentation.

[edit] Corals

Within the reef aquarium hobby, enthusiasts regularly fragment corals for a multitude of purposes including shape control; selling to, trading with, or sharing with others; regrowth experiments; and minimizing damage to natural coral reefs. Both hard and soft corals can be fragmented, with the level of success depending on the skill of the aquarist, method used, tolerance of the specific species, and conditions of care. Genera that have shown to be highly tolerant of fragmentation include Acropora, Montipora, Pocillopora, Euphyllia, and Caulastrea among many others.

[edit] Disadvantage of this process of reproduction

As this process is a form of asexual reproduction, it does not produce genetic diversity in the offspring. Therefore, these are more vulnerable to changing environments.

[edit] See also

[edit] References

  1. ^ Rood, S.B., Kalischuk, M.L., and Braatne, J.H. 2003. Branch propagation, not cladoptosis, permits dispersive, clonal reproduction of riparian cottonwoods. Forest Ecology and Management 186: 227â242. [1]

((Binary Fission)) ((Budding))




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