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Bee Pollen: Benefits, Side Effects, Uses, Dosage, Warnings?

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BEE POLLEN: Benefits, Side Effects, Uses, Dosage, Warnings?

The pollen (from the Greek πάλη ( LEAP ): flour or dust ) is, in higher plants, the male fertilizing element of the flower : they are tiny grains of more or less ovoid few tens of micrometers in diameter, initially contained in the anther at the end of the stamens .

The pollen grain is not a gamete but a gametophyte in itself, that is to say, a producer of gamete. You can not make an analogy between the pollen grain and egg because the egg is not a gametophyte itself, but a macrosporange containing a gametophyte.

The counterpart of the pollen grain in lower plants ( algae , mosses , prothallus of ferns ) is the male gametophyte.

It corresponds to the phase haploid plant development.

In some flowering plants, germination of the pollen grain often begins before it leaves the microsporangium with generative cell forming the two cells "sperm" .

Summary [ hide ]
1 size, structure and appearance of the pollen
1.1 Chemical and Biochemical Composition
2 Pollination
3 Allergies
4 Measurement of pollen counts in the air
5 Palynologie
6 Notes and references
7 See also
7.1 Bibliography
7.2 Related articles
7.3 External Links
Size, structure and appearance of pollen [ change | change the code ]

Pelottes fresh pollen reported by the honeybee

Anther of thale cress ladies ( Arabidopsis thaliana ) with pollen grains revealed by fluorescence micrograph.
About the size, it is considered that the smaller pollens are those of the Forget-Me (7 microns) and larger, those of squash (150 microns). Pollens under 10 microns are considered more etc.

Pollen can consist of a single grain (Monad inaperturate, porated, or Colpé colporé) or multiple grains (dyad, tetrad polyad) 1 .

The pollen grain is the gametophyte male. It appears in préspermaphytes , which therefore does not release the spores, as they remain sporophyte .

The mature pollen grain is usually made:

two or three cells not chambered. It has two cores haploid : the bigger the vegetative nucleus, the other generative or reproductive nucleus. Vegetative cell consists of a core, to organelles , small vacuoles and dried reserves ( starch , lipid droplets). Its primary function is to ensure the survival of the pollen grain, the second function to produce the pollen tube. The reproductive cell is small and surrounded by the eccentric vegetative cell. The ring is fused and blocked in prophase I of meiosis .
an external jacket, except in some aquatic plants submerged with:
highly resistant outer layer, the exine which is the exospore. It consists of sporopollenin . This layer includes apertures (weakest points, which allow the transmission of the pollen tube to fertilize the egg. exine The heavily cuticularisée resists most chemical and biological degradation, allowing the pollen to be released in environment without being damaged even if too nevertheless some pollen die quickly. THE ectexine is cellular and the other layers may be smooth ( spread by wind ) or ornamented ( cling to hair for animals, insect legs, etc. .
the ornaments of the exine in the form of thorns, indentations, "warts" hooks or species-specific patterns often allow the identification of genera, species, or even cultivar or individual. they make possible to identify the plant that produced the pollen grain, sometimes even millions of years after its production, which are the subject of palynology .
The inner layer that forms endospores. It is thin and brittle, consisting of cellulose unmodified and possibly other polysaccharides . It is called the intine.
Pollen provides food for browsers with bees which it is the main source of protein. It enters into the composition of royal jelly and honey .

Chemical and biochemical composition [ change | change the code ]
Pollen contains a high proportion of protein (16 to 40%) containing all the amino acids known. It also contains many vitamins , including Vitamin C , Vitamin E , Pro-vitamin A , niacin and many essential minerals including selenium (may contain up to 515% RDA). It is always present in small amounts in honey , which identifies its botanical origins. The bee uses the melissopalynology which is the science of honey and pollen. The carbohydrate levels vary by species from 15% to 75% usually in the center of France 2 , it is about 30% on average for all pollen flowers and 50% for example pollen date 3 . These carbohydrates are fructose , the glucose in a proportion that may itself vary much and sucrose "trained" to a lesser extent.

Pollination [ change | change the code ]

The bees, whose bee family belongs, are the most important pollinators
To germinate, the pollen grain must land on the pistil of a flower (female) of the same species.

The pollen transport : It is usually by a vector such as wind or insect : the pollination . The plant can also spread itself. Animals provide some targeting. The wind, however, no specificity. Plants which pollen is dispersed by the wind will therefore produce larger quantities. Similarly, when the mature stamens, pistil must be used also for the fertilization possible.

Germination of the pollen grain in angiosperms : Pollen must be retained by the stigma. For this, there are small electrostatic forces holding the grain or there are sticky substances (sugars). There are also specific links between the molecules of the pollen grain and the receiver at the stigma.

The pollen grain must be hydrated (water comes from the pistil). It will then be the first step in forming the pollen tube. At pore pollen: thinning is observed endexine during turgor, the pore of the pollen grain is pierced. The cell of the pollen tube then passes between the two cells of the stigma and style that have special (rather loose cells, cellulose walls unlignified, middle lamella rather hydrated with pectin liquefied appearance of spaces for the passage of the pollen tube).

Germination may be inhibited by mechanisms of incompatibility. There are different types of pollen incompatibility: Interspecies heteromorph, homomorphic (gametophytic or sprorophytique). Fertilization occurs in the opposite case, the tube until reaching the egg cell . Of the two male gametes:

A male gamete go with the egg cell (this will give the main egg diploid);
A male gamete go with one of the two polar nuclei that are diploid (which generate a triploid egg, will give the later albumen ).
This is what is called "double fertilization."

Allergies [ change | change the code ]
The presence of pollen grains (20-55 microns in diameter in general) in the atmosphere we breathe is normal (since much of the fertilization of plants is by anémogamie ). It is naturally higher in spring and summer in the temperate zone, and all year round in the tropics.

Some pollens cause allergies (called pollinosis ) in sensitized individuals.

This type of allergy ( rhinitis , asthma , conjunctivitis ) seems recent; described in England by Bostock (1819) at the beginning of the industrial era just before the first descriptions of allergic rhinitis are made ​​in 1830 in the Ruhr and in New England , while in France, no cases of hay fever has been described by the medical or scientific literature before 1860 4 . These rhinitis then appear in the world, apparently concomitantly (in space and time 5 ) the occurrence of massive chemical and particulate air pollution mainly due to coal and then to oil and chemicals, leaving think there is a link between air pollution and pollen allergenicity 6 (either because it is more sensitive, it is more allergenic, or both at once).

Since the end of the xix th century pollinoses seem steady progress at the same pace as overall air pollution and where the pollution appears or increases, especially in city traffic; This made ​​the hypothesis that factors other than the mere presence of pollen were involved including air pollution 7 .

In addition, since the 1970s, we observe a depletion (or near extinction, locally) pollinators (bees, butterflies in particular), other pollens, allergens or also potentially allergenic content are present in the air [style to review] .
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Studies have shown that in an artificial context these pollens are less fixed in the ground quickly, unless carried away by runoff or less absorbed by the foam or lichens in nature. These pollens are degraded by the action of the acidity of the air, ozone (superoxydant), other pollutants or for mechanical reasons (deposits on roadways and sidewalks) 8 . Smaller fragments (<2.5 microns, in the range of so-called PM2.5 fine particles that penetrate deeper into the lungs and deemed more allergens) are then trained and available for inhalation 8 . These include fragments of cuticles of pollen or pollen internal molecules 9 , which may become more allergens by combining with pollutants motor 10 . Found for example in air grains of starch , and known allergens associated with asthma epidemics thunderstorms during the pollen season various herbaceous 4 , 11 . Studies have also shown in vitro that intrapolliniques allergens (eg "Lol p I" ., a major allergen from the pollen of many herbaceous) combine (in our environment can be in microdroplets of water mist, rain and in aerosols ) to other fine particles allergens, also massively present during episodes of urban air pollution, especially fine carbon particles emitted by diesel engines in the form of carbon nanospheres from 30 to 60 nanometers (nm) in diameter grouping fractal spontaneously aggregates from about 1 to 2 micrometers (microns) in diameter 8 . This is one possible mechanism of concentration of allergens in the air, can trigger asthma attacks 8 . The diesel particulate stimulate the synthesis of IgE and cytokines involved in allergy and the sulfur dioxide and carbon monoxide, and especially ozone and nitrogen dioxide, this time directly as respiratory irritant may also weaken or strengthen the mucous membranes and prepare the inflammation allergic 4 . It also appears that the increase of CO2 in the air boosts pollen production (eg 130% in the ambrosia (especially allergen in France), compared to a pre-industrial atmospheric levels 12 )
Finally, lifestyle also seems relevant: if atopy is undeniably more important in urban areas, it was shown in Germany as hay fever and asthma were twice as frequent in the former West Germany than in the ancient inhabitants of the former East Germany, perhaps more susceptible to microbial stimulation in early childhood 13 (or less exposed to traffic?).

In France , the Institut Pasteur has its own cultures allergenic flowers that will be used to desensitize allergy sufferers and in 2013, the new program HANDLES includes a program on bee health , the veterinary drugs , the "cumulative risk of mixtures of pesticides " and possible interactions between pollen and air pollutants 14 .

Measuring the levels of pollen in the air [ change | change the code ]
Palynologists and network alerts and measurement of air pollution or organizations measuring the levels of pollen in the air benefit of remedies permitted by sensors pollens, whose samples are periodically analyzed. A pollen index can be produced and maintained and used for standby and prevention regarding the risk of allergy to pollen.

Pollen sensor to Lille

Detail

Pollen Index

Click on a thumbnail to enlarge
Palynology [ change | change the code ]
The palynology is the scientific study of pollens.

Pollen is often specific to a plant group ( family , genus ), sometimes the case : it is possible to identify a plant species by observing its pollen. The observed characteristics are size (from 2.5 to 200 microns ), the general shape and appearance of the exine: stratification, sculptures and grit from the surface, the number, shape and arrangement of apertures.

Applications of palynology are numerous:

palynology provides useful elements in studies of systematic plant;
the paléopalynologie is the study of pollen fossils : it allows to provide information on the climate and vegetation during the Quaternary ;
the aéropalynologie , which analyzes the presence in the air of different types of pollen, has applications in medicine ( allergic diseases ) and agriculture ( pollination );
the melissopalynology is the study of pollen present in the honey , which can detect mixtures and fraud.

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