Asexual Reproduction In Plants by: Danial Ahmed


1. Introduction:


Asexual reproduction is the formation of an individual from a single parent without the use of sex cells and does not undergo processes such as meoisis. (1) The genetic makeup and appearance of the offspring is identical to its parent. (1) Plants commonly asexually reproduce and therefore have an abundance of their population as they have certain advantages of this reproducing method. First of all, they do not have to receive genetic material from another source like pollen from another flower. They also do not have to worry about having genetic variability of the newly created individual being different from the parent. Also if there has been a stable environment for the parents over the years, it would not be essential for the new individuals to be genetically varied to survive. (2) Other benefits of asexually reproducing plants is that they require less energy and are not as complex as other organisms. (2) This allows them to reproduce without using a lot of energy. There are many benefits and positives to asexual reproduction in plants.

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imgAsexualSexualRepr.gif

The diagram on the right explicitly shows various methods of asexual reproduction such as binary fission. Another way asexual reproduction occurs is through the form of runners as well as hydra growing on certain organisms. The diagramon the left clearly reveals the different types of reproduction methods. It shows how asexual organisms like some plants have the same cells that are identical with the parent and the newly created individual. There is no genetic variability. Also, all the traits of the parent are consistent and the same in the offspring. It also shows how reproduction occurs between sexually reproducing organisms and how the genetic variability ofthe offspring is shared by half the traits of both parents.

2. Types of Asexual Reproduction in Plants:

2.1 Rhizomes:


One type of asexual reproduction that occurs often in plants is by the rhizomes which are underground horizontal stems of the plant. (3,4) The Rhizomes consists of many key parts to their structure including nodes, antinodes, scale leaves, axillary buds as well as adventituous roots, which provide it support. (3) The asexual reproduction of rhizomes is very unique. It occurs when the scale leaves are seen rising from the nodal points of the plant and eventually the axillary buds develop and grow into branches that spread out of the ground and create leaves. (3)The rhizomes continue to grow underground and strengthen the root of the newly created individual. This process continues amongst the plants and more are created in a short period of time. This is how this type of asexual reproduction occurs. Some common plants that experience this reproduction method are irises, tumeric and
ginger. (4)
ginger-rhizome.jpgroot-evolution.gif
This is a diagram outlining the steps it takes the plant to asexuallyreproduce using the rhizomes.
This is a diagram of a ginger rhizome, which details its significant part
which play a role in its asexual reproduction.

2.2 Tubers:

tuber.jpg
Tubers are another method how asexual reproduction occurs in plants. They are often considered modified and enhanced rhizomes. (5) They are a plant structure which saves energy for the parent plant. (5) Their task is very crucial as they store energy within the plant. Due to the energy stored in tubers, often people would eat them, to obtain more energy and strength. (6) There are two types of tubers, stem and root tubers. (5,6) Stem tubers form from underground rhizomes. An example would be the potato. Root tubers develop when sections of the roots swell and bud. (5) An example would be cassavas. For example, a new potato can be grown on its own when stem branches grow and reach into the ground, swelling up with starch containing cells. Buds on the tubers will eventually grow into new plants. If the budding also known as the eyes on the potato keep growing, they may even be able to create a separate potato if given the chance due to the growth and characteristic that it can store energy. (5,6) The holes in the diagram of the potato show some of the budding or "eyes".


2.3 Runners (Stolon):

Plant runners are a way in which some plants can asexually reproduce. For example, strawberries, ivy and spider plants all use this method. (7) A plant runner is a rapidly growing stem that grows above the ground and on the suface of the soil. (7) The mother parent of a strawberry plant for example runs along the surface and eventually, produces new individuals from the tip of its node. (7) As the new plant is slowly developing, the stems of the plant continue to take advantage of the rich soil and grow, while the roots begin to get stronger and support the newly created clone of the parent.strawberryrunner.jpg


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These diagrams show the formation of a new plant through the method of runners from a single parent.

2.4 Plantlets:

A simple yet effective way that plants such as duckweed use to asexually reproduce is through the method of plantlets. (6) Plantlets are formed when there are miniature plants established on the margin of the leaves. (6) Eventually these leaves break off, fall to the ground and continue growing on their own. (6) The growing success occurs due to sunlight, rich soil and water, and eventually the newly created individual resembles the appearance of the mother parent.
image006.gifMeristem%20to%20Plantlet.jpg

2.5 Bulb:

onion-bulb.jpgThe tasty vegetable that most people enjoy would indeed be the onions. This is one type of plant that uses the bulb method to asexually reproduce along with chives and lillies. (6,8) Each bulb has a stem, surrounded with leaves. (8) In the spring time, the shoot apex begins to grow utilizing the nutrients and energy stored in the leaves. (8) When the onion has contained the necessary nutrients from the parent, it slowly grows away from the parent and splits. (8) Eventually the newly created onion becomes an individual.Bulb_bw.gifimage008.jpg

2.6 Corms:


Corms are very similar to bulbs in appearance but the only difference is that they
do not have storage leaves. (9) Instead they have short and swollen stems, which store
energy for the plant. (9) Similarly the stem continues to grow and create a clone of the parent.

3. Asexual Plant Reproduction May Seed New Approach For Agriculture



Article link: http://esciencenews.com/articles/2010/03/08/asexual.plant.reproduction.may.seed.new.approach.agriculture


This article is very interesting and really focuses on the needs of society and how nature does play a role in our worldly needs. The main concern of the article was that how can sexually reproducing plants start to reproduce asexually. The article emphasized the amount of money the farmers have to devote towards farming and how it is not only expensive for them but for the entire society. Especially nowadays, the population is growing and we need more food to feed everyone. However, the plants have growing seasons, which slows down production and sexually reproducing plants take a greater time to develop. Whereas, asexual plants are created quickly and require less energy. The only drawback is that most asexually reproducing plants are not edible to consume or want to be consumed by the people. This is why Jean-Philippe Vielle-Calzada, a Howard Hughes Medical Institute (HHMI) international research scholar, wondered if he could apply the genetics of asexual plants to sexual plants to produce an abundance of plants in a short period of time. This was not only a very exciting project for him, but for agricultural companies as well. "Agricultural companies and farmers around the world have a tremendous interest in this method," says Vielle-Calzada. He started his research first looking in depth at apoximis, an asexual reproducing method used by nearly 350 types of flowering plant families, in which seeds are created without the formation of sperm and egg. He then research a small mustard plant, which reproduced sexually and wanted to induce apoximis into this plant.
He researched the mustard plant further and looked at the genes that were controlling the plant. One of them in particular was very interesting, Argonaute 9. Argonautes slice up the messenger RNA before it can be translated into proteins. They decided to mutate it and instead of the mustard plant making one gamete, it made several, which were all disturbed and dis-functional. He drew a conclusion that all plants have the potential to reproduce asexually, but Argonaute 9 is preventing it from happening. Him and his teams goal as of now is to see how to manipulate Argonaute 9 and dig in further to see how sexual plants can be converted to asexual methods. Over the years, he has obtained great success, but he will not settle until he proves this mystery between asexually and sexually reproducing plants.

After reading this article, it indeed sparked attention as to how important plants are for the entire society. They are a key factor for food as well as for beautification. They also have human uses as well as medicinal ones. This article is quite relative to the topic of asexual reproduction in plants because it enlightens and exposes the benefits of this method and how it significantly benefits the population. It is less costly and consumes less time. The thought and question is that how can sexually reproducing plants be more like asexual plants. This is the path society is steering towards today more than ever expected and hope to benefit significantly from this change from sexual to asexual if possible.

4. Links To Check Out:

http://www.scribd.com/doc/2410105/Asexual-Reproduction - powerpoint describing the attributes of an asexual reproducing organism

http://www.youtube.com/watch?v=drcnTg7ZCoc - video from youtube briefly explaining asexual reproduction

http://www.biologie.uni-hamburg.de/b-online/virtualplants/ipimovies.html - virtual plant animations

5. Glossary:


Adventitious Roots: Adventituous roots are roots in an unusual place, that originates from stem of leaf tissue rather than from another root, often where a branch or other part contacts soil or damp material.

Axillary Buds:The axillary bud is an embryonic shoot which lies at the junction of the stem and petiole of a plant.
Budding: Budding is a form of asexual reproduction in which a new organism grows on another one.

Cassavas:A shrubby tropical American plant (Manihot esculenta) widely grown for its large, tuberous, starchy roots.

Stolon: A stolon is a specialized type of, horizontal above ground shoot from an axillary bud near the base of the plant.

6. References:

1. Biology Class Notes Regarding Asexual Reproduction

2. Kimball John. Asexual Reproduction [Internet]. N/A: N/A; 1994 [cited 2012 Jan 16].
Available from: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/W/Welcome.html

3. Iannotti Marie. What is a Plant Rhizome? [Internet]. N/A: The New York Times Company; N/A [cited 2012 Jan 16]. Available from: http://gardening.about.com/od/floweringbulbs/g/Rhizome.htm

4. Ellis-Christensen Tricia. What is a Rhizome? [Internet]. N/A: Conjecture Corporation; 2011Sept 22 [cited 2012 Jan 16]. Available from: http://www.wisegeek.com/what-is-a-rhizome.htm

5. Smith S.E. What is a Tuber? [Internet]. N/A: Conjecture Corporation; N/A [cited 2012 Jan 16]. Available from: http://www.wisegeek.com/what-is-a-tuber.htm

6. Simmons Kent. Reproduction in Flowering Plants [Internet]. N/A: University of Winnipeg; N/A
[cited 2012 Jan 16]. Available from:http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb4pg6.htm

7. Winslow Jacqueline. What is a Plant Runner [Internet]. N/A: Demand Media Inc; N/A
[cited 2012 Jan 16]. Available from: http://www.ehow.com/facts_4927407_what-plant-runner.html

8. Wachman Monica. Forms of Asexual Reproduction in Plants [Internet]. N/A: eHow; N/A
[cited 2012 Jan 16]. Available from: http://www.ehow.com/list_6621877_forms-asexual-reproduction-plants.html

9. Mackean D. G. Plants: Introduction to Vegetative Reproduction [Internet]. N/A: N/A; N/A
[cited 2012 Jan 16]. Available from: http://www.biology-resources.com/plants-vegetative-reproduction-01.html