Pollination: Difference between revisions

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-[[Image:Bee carpenter with pollen.jpg|thumb|250px|[[Carpenter bee]] with pollen collected from [[Night-blooming cereus]]]]
-'''Pollination''' is an important step in the [[reproduction]] of [[seed plant]]s: the transfer of [[pollen|pollen grains]] (containing the male gametes) to the plant [[carpel]], the structure that contains the [[ovule]] (female gamete). The receptive part of the carpel is called a ''[[carpel|stigma]]'' in the [[flower]]s of [[flowering plant|angiosperm]]s and a ''micropyle'' in [[gymnosperm]]s. The study of pollination brings together many disciplines, such as [[botany]], [[horticulture]], [[entomology]], and [[ecology]]. Pollination is important in horticulture because most plant [[fruit]]s will not develop if the ovules are not [[fertilisation|fertilized]]. The pollination process as interaction between flower and [[Vector (biology)|vector]] was first addressed in the 18th century by [[Christian Konrad Sprengel]].
-== Types ==
-The process of pollination requires [[pollinator]]s: agents that carry or move the pollen grains from the [[Stamen|anther]] to the receptive part of the carpel. The various flower traits that attract different pollinators are known as [[pollination syndrome]]s. Methods of pollination, with common pollinators or plants, are:
-[[Image:Bees Collecting Pollen 2004-08-14.jpg|250px|thumb|Honey bee, pollinating.]]
-'''Biotic pollination''' occurs when pollination is mediated by an organism, termed a [[pollinator]]. '''[[Entomophily]]''', pollination by [[insect]]s, often occurs on plants that have developed  blue petals and a strong scent to attract insects such as, bees, wasps and occasionally ants ([[Hymenoptera]]), [[beetle]]s ([[Coleoptera]]), moths and butterflies ([[Lepidoptera]]), and flies ([[Diptera]]). In '''[[Zoophily]]''', pollination is done by vertebrates such as [[birds]] and [[bats]], particularly, [[hummingbird]]s, [[sunbird]]s, [[spiderhunter]]s, [[honeyeater]]s, and [[fruit Bat]]s. Plants adapted to this strategy tend to develop red petals to attract birds and rarely develop a scent because few birds have a sense of smell.
-'''Abiotic pollination''' occurs when pollination is mediated without the involvement of other organisms. For example, '''[[anemophily]]''' is pollination by [[wind]]. This form of pollination is very common in [[Poaceae|grasses]], most [[conifer]]s, and many deciduous trees. '''[[Hydrophily]]''' is pollination by [[water]] and occurs in aquatic plants which release their seeds directly into the surrounding water. About 80% of all plant pollination is [[biotic]].  Of the 20% of [[abiotic]]ally pollinated species, 98% is by wind and 2% by [[water]].
-== In agriculture ==
-[[Image:bee pollenating a rose.jpg|thumb|200px|right|An ''[[Andrena]]'' bee collects pollen among the [[stamens]] of a [[rose]]. The female [[carpel]] structure appears rough and globular to the left. The bee's stash of pollen is on its hind leg.]]
-[[Pollination management]] is a branch of agriculture that seeks to protect and enhance present pollinators and often involves the culture and addition of pollinators in [[monoculture]] situations, such as commercial fruit [[orchard]]s. The largest managed pollination event in the world is in [[California]]n [[almond]] orchards, where nearly half (about one million [[beehive (beekeeping)|hives]]) of the US [[honey bee]]s are trucked to the almond orchards each spring. [[New York]]'s [[apple]] crop requires about 30,000 hives; [[Maine]]'s [[blueberry]] crop uses about 50,000 hives each year.
-Bees are also brought to commercial plantings of [[cucumber]]s, [[squash (fruit)|squash]], [[melon]]s, [[strawberry|strawberries]], and many other crops. Honey bees are not the only managed pollinators: other [[species]] of bees are also raised as pollinators. The [[alfalfa leafcutter bee]] is an important pollinator for [[alfalfa]] [[seed]] in western [[United States]] and [[Canada]]. [[Bumblebee]]s are increasingly raised and used extensively for [[greenhouse]] [[tomato]]es and other crops.
-[[Image:Blackberry fruit formation 0698.JPG|thumb|right|200px|Well-pollinated blackberry blossom begins to develop fruit. Each incipient [[drupelet]] has its own [[carpel|stigma]] and good pollination requires the delivery of many grains of pollen to the flower so that all drupelets develop.]]
-The [[ecology|ecological]] and financial importance of natural pollination by insects to [[agriculture|agricultural]] [[Crop (agriculture)|crops]], improving their quality and quantity, becomes more and more appreciated and has given rise to new financial opportunities. The vicinity of a [[forest]] or wild [[grassland]]s with native pollinators near agricultural crops, such as apples, almonds or [[coffea|coffee]] can improve their yield by about 20%. The benefits of native pollinators may result in forest owners demanding payment for their contribution in the improved crop results - a simple example of the economic value of ecological services.
-The [[American Institute of Biological Sciences]] <ref>BioScience'', April 2006, Vol. 56 No. 4, pp. 315-317</ref> reports that native insect pollination saves the [[United States of America|United States]] [[Agriculture|agricultural]] economy nearly an estimated $3.1 billion annually through natural crop production.
-Pollination of food crops has become an [[environmental movement|environmental issue]], due to two trends. The trend to [[monoculture]] means that greater concentrations of pollinators are needed at bloom time than ever before, yet the area is [[forage (honeybee)|forage]] poor or even deadly to bees for the rest of the season. The other trend is the [[pollinator decline|decline of pollinator populations]], due to [[pesticide]] misuse and overuse, new diseases and [[parasite]]s of bees, [[clearfelling|clearcut logging]], decline of beekeeping, [[suburb]]an development, removal of [[hedge]]s and other [[Habitat (ecology)|habitat]] from [[farm]]s, and public [[paranoia]] about bees. Widespread [[agricultural aircraft|aerial spraying]] for [[mosquito]]es due to [[West Nile fever|West Nile]] fears is causing an acceleration of the loss of pollinators.
-The US solution to the pollinator shortage, so far, has been for commercial beekeepers to become pollination [[independent contractor|contractor]]s and to migrate. Just as the [[combine harvester]]s follow the [[wheat]] [[harvest]] from [[Texas]] to [[Manitoba]], beekeepers follow the bloom from south to north, to provide pollination for many different crops.
-=== Pollinators and pollenizers ===
-Pollination also requires consideration of [[pollenizer]]s. (The terms "pollinator" and "pollenizer" are often confused: a '''''pollinator''''' is the agent that moves the pollen, whether it be wind, bees, bats, moths, or birds; a '''''pollenizer''''' is the plant that provides the pollen.) Some plants are '''[[Self-incompatibility in plants|self-fertile]]''' or '''self-compatible''' and can pollinate themselves. Other plants have chemical or physical barriers to [[self-pollination]] and need to be cross-pollinated: with these self-infertile plants, not only pollinators must be considered but pollenizers as well. In pollination management, a good pollenizer is a plant that provides compatible, viable and plentiful pollen and blooms at the same time as the plant that is to be pollinated.
-Pollination can be '''cross-pollination''' with a pollinator and an external pollenizer, '''self-pollenization''' with a pollinator, or '''self-pollination''' without any pollinator:
-* Cross-pollination ('''''syngamy'''''): pollen is delivered to a flower of a different plant. Plants adapted to outcross or cross-pollinise have taller stamens than carpels to better spread pollen to other flowers.
-[[Image:Hummingbird in ggp 7.jpg|thumb|right|250px|A [[hummingbird]] feeding, as pollen flies around.]]
-* Self-pollenization ('''''autogamy'''''): pollen moves to the female part of the same flower, or to another flower on the same individual plant. This is sometimes referred to as self-pollination, but this is not synonymous with autogamy. Clarity requires that the term "self-pollination" be restricted to those plants that accomplish pollination without an external pollinator (example: the stamens actually grow into contact with the pistil to transfer the pollen). Most [[peach]] varieties are autogamous, but not truly self-pollinated, as it is generally an insect pollinator that moves the pollen from anther to stigma. Plants adapted to self-fertilize have similar stamen and carpel length.
-*'''''Cleistogamy''''': pollination that occurs before the flower opens is always self-pollination.  Some ''cleistogamous'' flowers never open, in contrast to '''''chasmogamous''''' flowers that open and are then pollinated. Cleistogamous flowers must of necessity be self-compatible or self-fertile plants. Other plants are self-incompatible. These are end points on a continuum, not absolute points.
-'''[[Hybrid (biology)|Hybridization]]''' is effective pollination between flowers of different [[species]] of the same [[genus]], or even between flowers of different genera (as in the case of several [[orchid]]s).
-[[Peach]]es are considered self-fertile because a commercial crop can be produced without cross-pollination, though cross-pollination usually gives a better crop. Apples are considered self-incompatible, because a commercial crop must be cross-pollinated. Remember that most fruits are [[grafting|grafted]] [[cloning|clone]]s, [[genetics|genetically]] identical. An orchard block of apples of one variety is in effect all one plant. Growers now consider this a mistake. One means of correcting this mistake is to graft a limb of an appropriate pollenizer (generally a variety of [[crabapple]]) every six trees or so.
-=== Honey bee pollination ===
-{{main|List of plants pollinated by bees}}
-[[Honey bee]]s travel from flower to flower, collecting [[nectar]] (later converted to [[honey]]), and pollen grains. The bee collects the pollen by rubbing against the anthers. The pollen collects on the hind legs, in dense hairs referred to as a '''[[pollen basket]]'''. As the bee flies from flower to flower, some of the pollen grains are transferred onto the stigma of other flowers.
-[[Image:European honey bee extracts nectar.jpg|thumb|right|250px|A bee collects nectar, while pollen collects on its body.]]
-Nectar provides the energy for bee [[nutrition]]; pollen provides the [[protein]]. When bees are rearing large quantities of [[brood (honey bee)|brood]] (beekeepers say hives are "building"), bees deliberately gather pollen to meet the nutritional needs of the brood. A honey bee that is deliberately gathering pollen is up to ten times more efficient as a pollinator than one that is primarily gathering nectar and only unintentionally transferring pollen.
-Good pollination management seeks to have bees in a "building" state during the bloom period of the crop, thus requiring them to gather pollen, and making them more efficient pollinators. Thus the management techniques of a [[beekeeper]] providing pollination services are different from, and somewhat incompatible with, those of a beekeeper who is trying to produce honey.
-Other species of bees differ in various details of their behavior and pollen-gathering habits, and it should be remembered that honey bees are not native to the [[Western Hemisphere]]; all pollination of native plants in the Americas has been historically performed by various native bees.
-==== Number of hives needed per acre (4,000 m²) of crop pollination ====
-<!-- This is getting far too specific and needs to be moved somewhere else -->
-[[Image:Pumpkin pollination4365.jpg|250px|thumb|Placing honey bees for pumpkin pollination in [[Mohawk Valley]], [[NY]]]]
-:Apples: 1&ndash;2
-:Blueberries: 4
-:Cantaloupe: 2&ndash;4
-:Cucumber 1&ndash;2
-:Squash: 1
-:Watermelon: 1&ndash;3
-It is estimated that about one hive per acre will sufficiently pollinate watermelons. In the 1950s when the woods were full of wild bee trees, and beehives were normally kept on most [[South Carolina]] farms, a farmer who grew ten acres (40,000 m²) of watermelons would be a large grower and probably had all the pollination needed. But today's grower may grow 200 acres (800,000 m²), and, if lucky, there might be one bee tree left within range. The only option in the current economy is to bring beehives to the field during blossom time.
-'''''Source:''''' Delaplaine et al. 1994, Bee pollination of Georgia crop plants. ''CES Bulletin 1106''.
-==See also==
-{{commonscat|pollination}}
-*[[Fruit tree pollination]]
-*[[Hand pollination]]
-*[[List of plants pollinated by bees]]
-*[[Self-pollination]]
-*[[Pollination syndrome]]s
-*[[Monsanto Canada Inc. v. Schmeiser]] - A Supreme Court of Canada lawsuit involving a farmer who was sued by Monsanto for having genetically modified plants on his farm.  The farmer claimed that the wind blew the seeds onto his land, and therefore did not violate any patents.
-==References==
-{{Reflist}}
-* Dafni, Amots; Kevan, Peter G.; and Husband, Brian C. (2005). ''Practical Pollination Biology''. Enviroquest, Ltd. ISBN 978-0-9680123-0-7.
-== External links ==
-{{Wiktionary}}
-*[http://dels.nas.edu/pollinators New "Pollinator Garden Wheel" from the National Academies provides information on pollination and tips on building a pollinator-friendly garden.]
-* [http://www.beeculture.com/content/pollination_handbook/index.cfm Insect Pollination Of Cultivated Crop Plants by S. E. McGregor  USDA 1972] (needs updating but still valuable)
-* [http://pollinator.com The Pollination Home page]
-* [http://www.pulseplanet.com/archive/May98/1625.html Pulse of the Planet description of buzz pollination]
-* [http://www.cas.vanderbilt.edu/bioimages/pages/pollination.htm Pollination syndromes images at bioimages.vanderbilt.edu]
-{{-}}
-{{Botany}}
-[[Category:Symbiosis]]
-[[Category:Pollination]]
-[[ar:تلقيح]]
-[[bs:Oprašivanje]]
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-[[ca:Pol·linització]]
-[[cs:Opylení]]
-[[da:Bestøvning]]
-[[de:Bestäubung]]
-[[es:Polinización]]
-[[eo:Polenado]]
-[[fr:Pollinisation]]
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-[[hr:Oprašivanje]]
-[[id:Penyerbukan]]
-[[it:Impollinazione]]
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-[[lt:Apdulkinimas]]
-[[nl:Bestuiving]]
-[[ja:受粉]]
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-[[ru:Опыление]]
-[[simple:Pollination]]
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-[[sv:Pollinering]]
-[[vi:Thụ phấn]]
-[[uk:Запилення]]
-[[zh:授粉]]

Revision as of 00:25, 6 February 2008