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10.2: Pisum sativum: Pea Plant

Created by: CK-12

Status

Published prior to review.

Common Name

  • Pea Plant
  • Garden Pea

Description

Scientifically, the pea plant Pisum sativum may be once of the most important members of the plant kingdom. This plant was used by Gregor Mendel, the father of genetics, to develop the basic concepts of inheritance.

The pea plant, like all angiosperms, is classified as an autotroph, meaning it uses photosynthesis to convert the energy of the sun to glucose. This plant has been cultivated across the world for thousands of years. Also, it is a legume, so it has the ability to fix nitrogen through a symbiotic relationship with the bacteria, Rhizobium.

Pea Plants are useful for studying heredity due to the duality of their various phenotypes. For example, their flower color is purple or white, the seed form is round or wrinkled, or the stem is tall or short. This means that there are no intermediate phenotypes. Also, the male and female reproductive parts of the plant are enclosed in the same flower, and mating/pollination can be controlled. It can also grow easily and mature in a short period of time, which allows results to be obtained quickly. Mendel studied about 29,000 pea plants during his studies.

The taxonomic classification of P. sativum is as follows:

  • Domain: Eukarya
  • Kingdom: Plantae
  • Phylum: Anthophyta
  • Class: Eudiotyledones
  • Order: Fabales
  • Family: Fabaceae
  • Genus: Pisum
  • Species: P. sativum

Habitat

The pea plant can be grown in any area with moderate temperatures; it isn’t localized to any one ecosystem or biome. P. sativum can be found across the world today either in garden’s for personal use or for commercial sale. The plant is native to the eastern Mediterranean areas and began to grow in rocky areas, from the regions of Turkey east to Syria, Iraq, and Iran. The pea plant thrives at temperatures between 13-18°C (55-64°F), developing best in the spring, cool summers, or the beginning of fall.

Biology

Cell Biology

Like all plants, P. sativum is an autotroph, absorbing sunlight to start the photosynthesis process. Together with carbon dioxide and water, the plant produces glucose, releasing oxygen as a waste product. The pea plant is also known as a producer, forming the energy that will benefit itself and other organisms in the ecosystem. This energy is stored within the plant as the carbohydrate starch, which is a polysaccharide of thousands of glucose molecules bonded together.

The pea plant, like all vascular plants, uses a vascular system comprised of phloem and xylem to transport water, sugars and other substances. The pea plant cells have a central vacuole used to store water. The phloem is used to transport sugars and nutrients. The xylem is used to transport water.

Genetics

P. sativum has a large and complex genome. It contains 4,300 mega base pairs or 4,300,000,000 base pairs. The P. sativum’s genome contains 14 chromosomes. The Pea Plant was used by Gregor Mendel to develop of his two laws of genetics. These principles of Mendelian genetics are the foundation of modern genetics.

Mendel investigated seven different characteristics in pea plants including seed shape, flower color, stem size, pod shape and pod color. Mendel cross-pollinated pure-bred parent plants, referred to as the P-generation. The offspring of the P generation, called the F1 generation, all had phenotypes representing one parental characteristic. When individuals from the F1 were allowed to self-pollinate, the next generation, the F2 generation, had 3 of 4 individuals with one P generation characteristic, and 1 of 4 individuals with the other P generation characteristic. This led to Mendel's law of segregation. This law states that there are two factors controlling a given characteristic, one of which dominates the other, and these factors separate and go to different gametes when a parent reproduces.

Additional experiments analyzing two pea plant characteristics, such as pod shape and color, resulted in Mendel developing his second law, the law of independent assortment. This law states that factors controlling different characteristics are inherited independently of each other.

Evolution

Evolutionary scientists believe that the P. sativum first evolved in Egypt in the Nile Delta area around 4800-4400 BC. The Pea Plant has not evolved over time or from a specific organism but it has made adaptations. The adaptations that it has made over time are self-pollination, nitrogen fixation, and the development of xylem and phloem. Self- pollination allows the pea plant to reproduce without the need of an organism to move its pollen. The downside to self-pollination is that there is less of a chance for greater genetic variability and change.

Ecology

The pea plant’s ecological role in the environment is a producer.

The pea plant is able to carry-out nitrogen fixation because of a symbiotic relationship relationship with certain bacteria and fungus. The bacteria receive extra sugars that the pea plant has made through photosynthesis, and the bacteria provides the plant with nitrogen. The plant, like all organisms, incorporates the nitrogen into its nucleic acids. The fungus provides the plant with additional nutrients that it usually receives from the soil. The fungus also receives glucose from the plant.

Physiology

Like all plants, P. sativum has an alternation of generations life cycle. This type of life cycle has separate times when either the haploid or diploid organism is dominant. Like all angiosperms, the pea plant has separate male and female reproductive structures, though both are located in the same flower.

Like most vascular plants, P. sativum maintains homeostasis through the use of xylem and phloem, self-pollination, and nitrogen fixation. Since the pea plant is a legume, it has developed a relationship with the bacteria Rhizobium. This bacteria enters the roots of the pea plant and forms nodules. Through this symbiotic relationship, the bacteria receive carbohydrates and other substances in exchange for fixing/converting nitrogen gas. The pea plant obtains and produces glucose during the process of photosynthesis, which it supplies to the bacteria. The pea plant has also developed a symbiotic relationship with a fungus. The fungus provides the plant with additional nutrients from the soil, and the fungus receives sugars from the plant.

The development of plant vascular tissue, xylem and phloem, occurred when plants migrated onto land. This vascular system allowed for the movement of water up the plant, and sugars made in their leaves during photosynthesis down the plant. The xylem moves water and the phloem moves dissolved solutes like sugars and amino acids. With this adaptation, the pea plant, like all plants is able to grow taller.

Photosynthesis converts water and carbon dioxide into sugars and oxygen, with the help of sunlight. P. sativum has two separate layers in the walls of the pods that are involved in photosynthesis. The outer layer is used to collect carbon dioxide from the atmosphere, and the inner layer is used to collect carbon dioxide that is coming off from the developing seeds inside the pod.

References

Attribution

Authors

Christopher Vasquez

Supervising Faculty

Arami Yoon

Affiliation

Grover Cleveland High School, Reseda, CA

Status

  • Published prior to review.

Edit History

  • Created: May 25, 2012
  • Version 1.0 submitted to CK-12: May 25, 2012
  • CK-12 edits: in progress

Level

  • High School (grades 9-12)

Image Attributions

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Categories:

Grades:

6 , 7 , 8 , 9 , 10 , 11 , 12

Date Created:

Jul 08, 2013

Last Modified:

Aug 02, 2014
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