Getting to Know the Avocado

Avocado fruit

The avocado is believed to have originated in the state of Puebla, Mexico,[1][2] though fossil evidence suggests similar species were much more widespread millions of years ago, occurring as far north as California.[1][3]

The word "avocado" comes from the Spanish "aguacate", which in turn comes from the Nahuatl word "āhuacatl".[1][4] Sometimes the Nahuatl word was used with the meaning "testicle", probably because of the likeness between the fruit and the body part.[1][5]

The avocado matures on the tree, but ripens off the tree.[1]

The use of an ethylene gas "ripening room", which is now an industry standard, was pioneered in the 1980's in response to footage from a hidden supermarket camera which showed shoppers repeatedly squeezing hard, unripe avocados, putting them back, and moving on without making a purchase.[1][6][7]

A ripe avocado yields to gentle pressure when held in the palm of the hand and squeezed. The flesh is prone to enzymatic browning; it turns brown quickly after exposure to air.[1][16] To prevent this, lime or lemon juice can be added to avocados after they are peeled.

Pollination

The avocado is unusual in that the timing of the male and female flower phases differs among *cultivars. The two flowering types are 'A' and 'B'.[1][8] 

'A' cultivar flowers open as female on the morning of the first day and close in late morning or early afternoon. They then open as male in the afternoon of the second day.[1][9][10]

'B' varieties open as female on the afternoon of the first day, close in late afternoon and reopen as male the following morning.[1][9][10]

*In asexually propagated plants, a cultivar is a clone considered valuable enough to have its own name; in sexually propagated plants, a cultivar is a pure line (for self-pollinated plants) or, for cross-pollinated plants, a population that is genetically distinguishable.[11]

A seedless avocado, or 'cuke', growing 
next to two regular avocados.[1]

Commercial orchards produce an average of seven tonnes per hectare each year, with some orchards achieving 20 tonnes per hectare.[36] 

Certain cultivars have a tendency to bear well only in alternate years. In addition, due to environmental circumstances during some years, seedless avocados may appear on the trees.[1][12] Known in the avocado industry as "cukes", they are usually discarded commercially due to their small size.[1][13]

Young avocado plant (seedling),
complete with parted pit and roots.[1]

Avocados propagated by seed can take anywhere from four to ten years to bear fruit.[1][14]

Avocado trees are vulnerable to bacterial, viral, fungal, and nutritional diseases. Disease can affect all parts of the plant, causing spotting, rotting, cankers, pitting, and discoloration.[1][15]

The Upside of Avocados

Avocados have diverse fats.[1][17] For a typical avocado:

• About 75% of an avocado's energy comes from fat, most of which (67% of total fat) is monounsaturated fat as oleic acid.[1][17]
• Other predominant fats include palmitic acid and linoleic acid.[1][17]
• The saturated fat content amounts to 14% of the total fat.[1][17]

Typical total fat composition is roughly: 1% omega-3 fatty acid, 14% omega-6 fatty acid, 71% omega-9 fatty acid, and 14% saturated fat.[1][18]

On a weight basis, avocados have 35% more potassium (485 mg/100 g) than bananas (358 mg/100 g).[1] They are rich in folic acid, pantothenic acid, vitamin B6 and vitamin K, and are good dietary sources of other B vitamins, vitamin C and vitamin E.[1][17]

Avocados have a high fiber content of 75% insoluble and 25% soluble fiber.[1][19]

High avocado intake was shown in one preliminary study to lower blood cholesterol levels. Specifically, after a seven-day diet rich in avocados, mild hypercholesterolemia patients showed a 17% decrease in total serum cholesterol levels. These subjects also showed a 22% decrease in both LDL (harmful cholesterol) and triglyceride levels and 11% increase in HDL (helpful cholesterol) levels.[1][20]

The Downside of Avocados

Some people have allergic reactions to avocado. There are two main forms of allergy: those with a tree-pollen allergy develop local symptoms in the mouth and throat shortly after eating avocado; the second, known as latex-fruit syndrome,[1][21] is related to latex allergy[1][22] and symptoms include generalized rash and itchy welts, abdominal pain, and vomiting and can sometimes be life-threatening.[1][23]

Avocado leaves, bark, skin, or pit are documented to be harmful to animals; cats, dogs, cattle, goats, rabbits,[1][24]  rats, guinea pigs, birds, fish, and horses[1][25][26] can be severely harmed or even killed when they consume them. The avocado fruit is poisonous to some birds, and the American Society for the Prevention of Cruelty to Animals (ASPCA) lists it as toxic to many animals including cats, dogs, and horses.[1][27]

Avocado leaves contain a toxic fatty acid derivative, persin, which in sufficient quantity can cause colic in horses and, without veterinary treatment, death.[1][28]  Birds also seem to be particularly sensitive to this toxic compound. 

Evolutionary Anachronism 

Megatherium (ground sloth) was one of the
largest land mammals known, weighing up to
4 tonnes[33] and measuring up to 6 m in length
from head to tail.[34][35] 

In 1982, the evolutionary biologist Daniel H. Janzen suggested that the avocado may be an example of an 'evolutionary anachronism', a fruit adapted for an ecological relationship with now-extinct large mammals.[1]

Most large fleshy fruits serve the function of seed dispersal, accomplished via their consumption by large animals. There are some reasons to think that the fruit, with its mildly toxic pit, may have co-evolved with *Pleistocene megafauna to be swallowed whole and excreted in their dung, ready to sprout. No surviving native animal is large enough to effectively disperse avocado seeds in this fashion.[1][29][30]

*Pleistocene fauna in North America included giant sloths; short-faced bears; the American lion; giant condors;  saber-toothed cats; dire wolves; at least two species of bison; stag-moose; horses; mammoths; and giant tortoises. In contrast, today the largest North American land animal is the American bison.[31][32]

UPDATES / RELATED

The Fit Food Fruit: 7 Benefits Of Avocado For A Long, Healthy Life / Medical Daily / May 11. 2015

REFERENCES

[1] http://en.wikipedia.org/wiki/Avocado
[2] Galindo-Tovar, María Elena 5, Arzate-Fernández, Amaury M., Ogata-Aguilar, Nisao, and Landero-Torres, Ivonne (2007). "The Avocado (Persea Americana, Lauraceae) Crop in Mesoamerica: 10,000 Years of History". Harvard Papers in Botany. Harvard University Herbaria. Retrieved 2014-04-27.
[3] "Fossil avocado leaves found in California" (PDF). Retrieved 2014-08-25.
[4] Nahuatl Dictionary/Diccionario del náhuatl. Whp.uoregon.edu. Retrieved on 2013-07-25.
[5] "Online Etymology Dictionary". Etymonline.com. Retrieved 2014-02-01.
[6] "Ethylene gas and produce". Mindfully.org. 1976-06-01. Archived from the original on 26 May 2010. Retrieved 2010-05-12.
[7] Steve Chawkins (2013-06-03). "Gil Henry dies at 88; revolutionized avocado industry; Henry pioneered the use of a 'ripening room' at his family's Escondido farm. The method, now an industry standard, allows markets to sell fruit that is ready to eat or close to it.".Los Angeles Times. Retrieved 2013-06-04.
[8] http://en.wikipedia.org/wiki/Sequential_hermaphroditism
[9] Cultivar - Merriam-Webster Online www.merriam-webster.com/dictionary/cultivar
[10] "Agriculture Handbook". University of California. 2007. Archived from the original on 17 December 2007. Retrieved 2007-12-29.
[11] Crane, JH; Balerdi CF; Maguire I (2007-08-01). "Avocado Growing in the Florida Home Landscape". University of Florida. Archived from the original on 13 January 2008. Retrieved 2007-12-29.
[12] Blumenfeld, Amos; Gazit, Shmuel. "Development of Seeded and Seedless Avocado Fruit". Agricultural Research Organization, Volcani Center, Bet-Dagan, Israel. Retrieved2010-09-21.
[13] Stewart, W.S.; Smoyer, K.M.; Puffer, R.E. "Progress Report on Effects of Plant Growth Regulator Sprays on Avocados". California Avocado Society 1948 Yearbook 33: 113–116. Retrieved 2010-09-21.
[14] Boning, Charles (2006). Florida's Best Fruiting Plants: Native and Exotic Trees, Shrubs, and Vines. Sarasota, Florida: Pineapple Press, Inc. p. 33.
[15] Ohr, HD; Coffer MD & McMillan RT (2003-08-04). "Common Names of Plant Diseases". American Phytopathological Society. Archived from the original on April 23, 2008. Retrieved 2008-05-13.
[16] Jules Janick, ed. (2008). The Encyclopedia of Fruit & Nuts. Oxforshire, England: CABI. p. 440. ISBN 9780851996387.
[17] "Avocados, raw, all commercial varieties, per 100 grams". NutritionData.com. 2013.
[18] "Fatty acids found in avocado oil". Esoteric Oils. 14 November 2011.
[19] Naveh E, Werman MJ, Sabo E, Neeman I (2002). "Defatted avocado pulp reduces body weight and total hepatic fat but increases plasma cholesterol in male rats fed diets with cholesterol". J. Nutr. 132 (7): 2015–8. PMID 12097685.
[20] Lopez Ledesma, R; Frati Munari, A C: Hernandez Dominguez, B C: Cervantes Montalvo, S: Hernandez Luna, M H: Juarez, C: Moran Lira, S (Winter 1996). "Monounsaturated fatty acid (avocado) rich diet for mild hypercholesterolemia". Arch-Med-Res. 27 (4): 519–23.PMID 8987188.
[21] Brehler R, Theissen U, Mohr C, Luger T (April 1997). "Latex-fruit syndrome": frequency of cross-reacting IgE antibodies". Allergy 52 (4): 404–10. doi:10.1111/j.1398-9995.1997.tb01019.x. PMID 9188921.
[22] "Latex allergy". Better Health Channel.
[23] "Avocado - allergy information (InformAll: Communicating about Food Allergies - University of Manchester)". Inflammation-repair.manchester.ac.uk. 2006-10-18. Retrieved2014-08-25.
[24] Clipsham, R. "Avocado Toxicity". Archived from the original on 12 January 2008. Retrieved 2007-12-29.
[25] "Notes on poisoning: avocado". Canadian Biodiversity Information Facility. 2006-06-30.Archived from the original on 14 January 2008. Retrieved 2007-12-29.
[26] Appleman, D. (1944). "Preliminary Report on Toxicity of Avocado Leaves" (PDF). Retrieved 2012-10-09.
[27] "Avocado". ASPCA Animal Poison Control Center.
[28] Oelrichs PB, Ng JC, Seawright AA, Ward A, Schäffeler L, MacLeod JK (1995). "Isolation and identification of a compound from avocado (Persea americana) leaves that causes necrosis of the acinar epithelium of the lactating mammary gland and the myocardium".Nat. Toxins 3 (5): 344–9. doi:10.1002/nt.2620030504. PMID 8581318.
[29] Cited in Barlow, Connie C. (2000). The ghosts of evolution: nonsensical fruit, missing partners, and other ecological anachronisms. New York: Basic Books. ISBN 0-465-00551-9.
[30] Wolstenholme, B. N. and Whiley, A. W. (1999). "Ecophysiology of the avocado (Persea americana Mill.) tree as a basis for pre-harvest management". Revista Chapingo Serie Horticultura 5: 77–88.
[31] http://en.wikipedia.org/wiki/Pleistocene_megafauna
[32] Ice Age Animals
[33] Bargo, M. S. (2001). "The ground sloth Megatherium americanum: Skull shape, bite forces, and diet". Acta Palaeontologica Polonica 46 (2): 173–192. Retrieved 22 July2012.

[34]  "Megatherium Wildfacts". BBC. Retrieved 22 July 2012.

[35] Haines, T.; Chambers, P. (2007). The Complete Guide to Prehistoric Life. Italy: Firefly Books Ltd. pp. 192–193. ISBN 1-55407-181-X.

[36] Whiley, A (2000-09-01). "Avocado Production in Australia". Food and Agriculture Organization of the United Nations. Archived from the original on 12 January 2008. Retrieved 2007-12-29.

http://www.brainpickings.org/2013/12/04/avocado-ghosts-of-evolution/

"Ghosts of Evolution" https://www.youtube.com/watch?v=ZWW5OuxlKec

http://sciencelearn.org.nz/Contexts/Pollination/NZ-Research-Collection/Avocado-pollination

http://ucavo.ucr.edu/Flowering/FloweringBasics.html

http://www.smithsonianmag.com/arts-culture/why-the-avocado-should-have-gone-the-way-of-the-dodo-4976527/?no-ist

IMAGE CREDITS

"Avocado" by Unknown - http://web.archive.org/web/20060515202557/http://www.nass.usda.gov/fl/apfp.htm (Original link: http://www.nass.usda.gov/fl/apfp.htm). Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Avocado.jpeg#mediaviewer/File:Avocado.jpeg

"Avocado Seedling" by Mark Hofstetter - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Avocado_Seedling.jpg#mediaviewer/File:Avocado_Seedling.jpg

"Seedless Avocado in Mexico" by nsaum75¡שיחת!‎. Original uploader was Nsaum75 at en.wikipedia - Transferred from en.wikipedia; transferred to Commons by User:Nsaum75 using CommonsHelper.(Original text : I (nsaum75¡שיחת!‎) created this work entirely by myself.). Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Seedless_Avocado_in_Mexico.jpg#mediaviewer/File:Seedless_Avocado_in_Mexico.jpg

"Megatherum DB" by ДиБгд at Russian Wikipedia - Transferred from ru.wikipedia to Commons.. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Megatherum_DB.jpg#mediaviewer/File:Megatherum_DB.jpg