On page 78-79 of Dr. Moalem's "Survival of the Sickest", he describes that plants are the biggest manufacturer of chemical weapons in the world. In fact, plant chemistry has the power to significantly impact its' environment from weather to the amount of predators in the area. One such chemical is called phytoestrogen. This chemical mimics the effects of estrogen, a hormone. When animals eat too much of plants that contain phytoestrogen, the compound destroys the animals ability to reproduce.
An example of this is a sheep breeding crisis that occurred during the 1940s in western Australia. Healthy sheep were not getting pregnant. Agricultural specialist confirmed that the phenomenon occurred because of the European Clover (produces phytoestrogen aka formononetin). This occurs when the area doesn't have rain or sunshine, so it limits the amount of predators.
This correlates with Big Idea 1 which relates to natural selection. These plants relate to this big idea because the animals who eat the plants will survive, however, they will not reproduce, so the population for that organism will decrease exponentially. Those organisms who are aware of these types of plants will be the predators who can survive and reproduce off of a different plant.
What are some other types of chemical defense mechanisms that plants use? Please give the scientific name and a description of what the chemical does to its' surrounding environment. Also, can the overload of estrogen in animals causing havoc in reproductive abilities be cured? Please do outside research and explain how organisms can be cured.
Elliot Rosen (erosen3@students.d125.org)
After researching types of plant chemical defenses, I found that there were two main categories; primary metabolites and secondary metabolites. Primary metabolites are mainly involved in plant growth (ex. sugars, proteins, amino acids, and nucleic acids). Secondary metabolites are not involved in growth, but are more of the defensive end and belong to one of three large chemical classes (terpenoids, phenolics, and alkaloids).
ReplyDeleteTerpenoids are in all plants and they have over 22,000 compounds. One example, and the simplest form of Terpenoid, is the hydrocarbon isoprene (C5H8). It is a gas that is emitted during photosynthesis in large quantities by the leaves of a plant that helps protect the cell membranes from damage. Terpeniods are often classified by the number of isoprene units used to construct them.
Phenolics are also used to defend plants against pathogens. They are produced via the shikimic acid and malonic acid pathways in plants, which produce amino acids from carbohydrates. The compounds produced include a wide variety of defense related compounds (flavonoids, anthocyanins, phytoalexins, tannins, lignin, and furanocoumarins). These are all various defense mechanisms that in the end produce some kind of defense against pathogens.
Lastly, Alkaloids are the nitrogenous compounds that are derived from amino acids and effect not only the plant physiology, but also make it bitter-tasting to predators. Examples include caffeine, cocaine, morphine, and nicotine.
Although these compounds may have other uses on our daily lives, to predators they toxic and are a selective advantage to those who have these defenses. Therefore, this relates to This relates to Big Idea 1: The process of evolution drives the diversity and unity of life, because plants who have defensive mechanisms will be selected for and survives and reproduce.
Finally, because the overload of estrogen in animals causes havoc in the reproductive cycle, humans have developed a "cure" or what could be considered a temporary solutions that alleviate the problems, but do not eliminate them. These include living a healthy life (good diet and exercise), Dong Quai, L-Theanine, Black Cohosh, Fish or Krill Oil and Progesterone cream. Therefore, although these do not eliminate the hormone problem, they alleviate some of the symptoms and reduce the severity.
Sources:
"An Overview of Plant Defenses against Pathogens and Herbivores" by Brian C. Freeman and Gwyn A. Beattie from Iowa State University
Hormone Balance by Vera Tweed
(Dana Morgan, Dmorgan4@students.d125.org)
ReplyDeletePlant defenses against herbivores can include chemical or mechanical methods to avoid being eaten. Plant defenses also protect against pathogens. Some chemical defenses common to plants include trypsin inhibitors and peroxidase in addition to the metabolites previously mentioned. TI and POD levels increase in plants, specifically the Alliaria petiolata (garlic mustard) when the plant is damaged (Cipollini, 2002). Trypsin inhibitors deter herbivores because they are protease inhibitors, which disrupt proteases in insects. Protease aids in hydrolysis of peptide bonds so the organism can use the amino acids from a food source. Peroxidase is an enzyme that converts hydrogen peroxide into water and oxygen. In plants, it switches on the hypersensitive response to kill infected cells and keep a pathogen contained.
These chemical defenses give a plant a selective advantage (Big Idea 1). By conditioning herbivores with TI to stop ingesting a plant because of it’s nasty chemical side affects, the other individuals of the species can avoid being eaten. Those plants will survive long enough to reproduce. Plants with peroxidase are able to avoid infection and therefore also live to survive and reproduce.
In animals, an overload of estrogen is paired with a lack of progesterone. These two hormones have a yin-yang relationship. Too much estrogen can cause “havoc” (problems with fertility). Problems range from ovarian cysts that hinder the body’s ability to reproduce and also complete infertility. Damage that causes infertility is often irrevocable. Treatments, but not cures, are available, including progesterone supplements to balance hormone levels in addition to the treatments mentioned in the previous post.
Source:
Variation in the Expression of Chemical Defenses in Alliaria petiolata (Brassicaceae) in the Field and Common Garden
Don Cipollini
American Journal of Botany , Vol. 89, No. 9 (Sep., 2002), pp. 1422-1430
Published by: Botanical Society of America
Article Stable URL: http://www.jstor.org/stable/4124059
(Katelyn Noronha, knoronh4@students.d125.org)