What is asexual reproduction?
Asexual reproduction in plants occurs by mitosis of diploid cells, producing clones (genetically identical individuals).
It is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that single parent only; it does not involve meiosis or fertilization.[1]
external image rhizome_example.png

Structure

Plants use a variety of structures for asexual reproduction, a few of them being modified leaves, modified stems, plant fragments and roots. Normal leaves are assigned to certain functions such as photosynthesis
external image homology_leaves.gifand transportation. [2] When leaves perform functions other than photosynthesis and transportation, they are called modified leaves because of the structural changes. An example for a modified leaf is a bud scale. Bud scales are tough overlapping waterproof leaves that protect buds from frost and pathogens.[3] Modified stems fall under the same definition. There are a variety of stems for different purposes such as rhizomes; they produce underground stems from which new plants grow.[4] Corms, stolons and the eyes on tubers are also examples of modified stems.[5] New plants can also grow from fragments of plants and roots.

Costs and Benefits of Asexual Reproduction

There are a variety of reasons of plants plants reproduce asexually, a few benefits being:
  1. Some plants have certain traits that allow it to survive in a specific environment, and since plants reproduce asexually its offspring with be given the exact same traits to survive and take advantage of all the resources in that environment.[6][7]
  2. The reproduction takes less time and energy (producing offspring more rapidly) because it does not have to produce specialized reproductive structures.
  3. For asexual reproduction only one plant is needed whereas for sexual reproduction both male and female plants are necessary in the making of an offspring.external image images?q=tbn:ANd9GcRFByVVdXRpnhjCIXYfog22fR_ACCZIVS5h3SRbB32VKBA_2pPsfA
  4. Plantlets have a higher survival rate because they're more healthy and strong than young seedlings.[8]
Although there are many benefits to reproducing asexually, there is one big downside to it in addition to lacking variation of plants. Due to the fact that the environment only selects those plants with the traits to reproduce and survive in the environment, the population is identical. If the environment changes greatly, the plants could die because their traits don't allow them to survive under those new conditions and would not allow them to reproduce in the new environment.[9] In order to try to survive, the individuals, take for example grass plants that are produced asexually, would eventually begin to produce sexually by creating flowers and seeds.[10]



Human Uses of Asexual Reproduction

Humans manipulate asexual reproduction in a variety of ways. Farmers use various plant structures to grow more plants as well as growing copies of plants that have desirable characteristics. One of the most common methods that farmers, commercial nurseries and gardeners use to clone plants is to take a cut stem (this process is known as stem cutting) and then place it in water.[11] [12] The plant quickly grows roots and then is able to be transferred back into the soil to continue growing. Growers also use techniqu
external image Cleft_graft.jpges that do not occur naturally such as grafting. Grafting is when a young branch with desirable characteristics is then attached to a stem of the same species or closely related to create multiple plants with those same characteristics.[13] In order for the grafting to work, the cellular plant tissue of the scion and the cellular plant tissue of the stock grow together so that both tissues fuse with one another.[14] An example of grafting are grape vines. grafting grape vines allows the grower to get the same results year after with the desirable characteristics of the scion. The only downside to grafting is that there is a lack in the diversity between the plants.

Mini Quiz

  1. Name two of the structures used for asexual reproduction. Give an example of each.
  2. What are three benefits of reproducing asexually? What is the downside?
  3. How would an asexual plant survive if the environmental conditions significantly changed?
  4. What are two human uses of asexual reproduction?
  5. What is grafting? Explain the process.

Did you know...

  • there are many types of asexual reproduction: binary fission, budding, fragmentation, spore formation and parthenogenesis[15]
  • plants that reproduce asexually are multi-cellular organisms
  • offspring are genetically identical to the parent

Glossary

Rhizomes: A horizontal, usually underground stem that often sends out roots and shoots from its nodes.
Specialized Reproductive Structures: involve seed plants, plants with flowers

Scion: young detached branch with desirable characteristics
Stock: the plant onto which a scion is grafted on


Answers for mini quiz

  1. modified leaves, modified plants, plant fragments and roots (any of the two)
  2. Benefits: have certain traits allowing to survive in specific environment, reproduce more rapidly than sexual plants, only one plant is needed, plantlets have higher survival rate due to the fact that they are more robust. Downside: no variation, if environment drastically changes plants will not survive.
  3. it would survive by becoming sexual by producing flowers and seeds.
  4. grafting, stem cutting.
  5. where tissues from one plant with desirable characteristics (scion) is attached to a plant of the same species/closely related to produce a plant with the same desirable characteristics.


References
  1. ^ Dulson J, Fraser D, LeDrew B, Vavitsas A. Biology 11. University Preparation. Toronto: Nelson; 592-594p.
  2. ^



    Dulson J, Fraser D, LeDrew B, Vavitsas A. Biology 11. University Preparation. Toronto: Nelson; 592-594p.
  3. ^
    "modified stems." Backyard Nature with Jim Conrad. N.p., n.d. Web. 17 June 2012. <http://www.backyardnature.net/stemtype.htm>.
  4. ^
    "modified stems." Backyard Nature with Jim Conrad. N.p., n.d. Web. 17 June 2012. <http://www.backyardnature.net/stemtype.htm>.
  5. ^ "modified stems." Backyard Nature with Jim Conrad. N.p., n.d. Web. 17 June 2012. <http://www.backyardnature.net/stemtype.htm>.
  6. ^ Dulson J, Fraser D, LeDrew B, Vavitsas A. Biology 11. University Preparation. Toronto: Nelson; 592-594p.
  7. ^ "Discuss the advantages and disadvantages of asexualreproduction by making reference to different types of asexualreproduction in plants and animals(Refer to cloning, binaryfission, formation, vegetative reproduction, parthenogenesis,budding and fragm." ThinkQuest : Library. N.p., n.d. Web. 17 June 2012. <http://library.thinkquest.org/22016/contribute/asex_sex.htm>
  8. ^ "Discuss the advantages and disadvantages of asexualreproduction by making reference to different types of asexualreproduction in plants and animals(Refer to cloning, binaryfission, formation, vegetative reproduction, parthenogenesis,budding and fragm." ThinkQuest : Library. N.p., n.d. Web. 17 June 2012. <http://library.thinkquest.org/22016/contribute/asex_sex.htm>
  9. ^


    "Discuss the advantages and disadvantages of asexualreproduction by making reference to different types of asexualreproduction in plants and animals(Refer to cloning, binaryfission, formation, vegetative reproduction, parthenogenesis,budding and fragm." ThinkQuest : Library. N.p., n.d. Web. 17 June 2012. <http://library.thinkquest.org/22016/contribute/asex_sex.htm>
  10. ^
    Dulson J, Fraser D, LeDrew B, Vavitsas A. Biology 11. University Preparation. Toronto: Nelson; 592-594p.
  11. ^


    Dulson J, Fraser D, LeDrew B, Vavitsas A. Biology 11. University Preparation. Toronto: Nelson; 592-594p.
  12. ^ "Stem cutting." Cactus-art. N.p., n.d. Web. 17 June 2012. <http://www.cactus-art.biz/note-book/Dictionary/Dictionary_S/dictionary_stem_cutting.htm>.
  13. ^


    "Grafting ." North Carolina Cooperative Extension: Home. N.p., n.d. Web. 17 June 2012. <http://www.ces.ncsu.edu/depts/hort/hil/grafting.html>.
  14. ^
    "Grafting ." North Carolina Cooperative Extension: Home. N.p., n.d. Web. 17 June 2012. <http://www.ces.ncsu.edu/depts/hort/hil/grafting.html>.
  15. ^ "Different Types of Asexual Reproduction | Tutorvista.com." Tutorvista.com - Online Tutoring, Homework Help for Math, Science, English from Best Online Tutor. N.p., n.d. Web. 17 June 2012. <http://www.tutorvista.com/content/biology/biology-iv/reproduction-in-animals/asexual-reproduction-types.php>