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It is Spring...

If you are lucky enough to live away from the city or large industrial areas, you can breath a sign of relief.  The smell of clean and fresh air rejuvenates you.  Unless, you are down wind from a farm, then you will sniff  the farmers gold, manure that is, which he distributes over his plowed land before he plants the seeds.  But this is only for a short time, a small price to pay for the beauty that surrounds you.   Unless you are allergic to pollen, also known as hay fever.  Here is information about pollen that could be useful.

What is pollen?

Plants produce microscopic round or oval pollen grains to reproduce. In some species, the plant uses the pollen from its own flowers to fertilize itself. Other types must be cross-pollinated; that is, in order for fertilization to take place and seeds to form, pollen must be transferred from the flower of one plant to that ofanother plant of thesame species. Insects do this job for certain flowering plants, while other plants rely on wind transport

The types of pollen that most commonly cause allergic reactions are produced by the plain-looking plants (trees, grasses, and weeds) that do not have showy flowers.  These plants manufacture small, light, dry pollen granules that are custom-made for wind transport. Samples of ragweed pollen have been collected 400 miles out at sea and two miles high in the air. Because airborne pollen is carried for long distances, it does little good to rid an area of an offending plant–the pollen can drift in from many miles away. In addition, most allergenic pollen comes from plants that produce it in huge quantities. A single ragweed plant can generate a million grains of pollen a day.

The chemical makeup of pollen is the basic factor that determines whether it is likely to cause hay fever. For example, pine tree pollen is produced in large amounts by a common tree, which would make it a good candidate for causing allergy. The chemical composition of pine pollen, however, appears to make it less allergenic than other types. Because pine pollen is heavy, it tends to fall straight down and does not scatter. Therefore, it rarely reaches human noses.

Among North American plants, weeds are the most prolific producers of allergenic pollen.  Ragweed is the major culprit, but others of importance are sagebrush, redroot pigweed, lamb’s quarters, Russian thistle (tumbleweed), and English plantain.

Grasses and trees, too, are important sources of allergenic pollens. Although more than 1,000 species of grass grow in North America, only a few produce highly allergenic pollen. These include timothy grass, Kentucky bluegrass, Johnson grass, Bermuda grass, redtopgrass, orchard grass, and sweet vernal grass. Trees that produce allergenic pollen include oak, ash, elm, hickory, pecan, box elder, and mountain cedar.

It is common to hear people say that they are allergic to colorful or scented flowers like roses. In fact, only florists, gardeners, and others who have prolonged, close contact with flowers are likely to become sensitized to pollen from these plants. Most people have little contact with the large, heavy, waxy pollen grains of many flowering plants because this type of pollen is not carried by wind but by insects such as butterflies and bees.

When do plants make pollen?

One of the most obvious features of pollen allergy is its seasonal nature, people experience  symptoms only when the pollen grains to which they are allergic are in the air.  Each plant has a pollinating period that is more or less the same from year to year.  Exactly when a plant starts to pollinate seems to depend on the relative length of night and day, and therefore on geographical location, rather than on the weather.  On the other hand, weather conditions during pollination can affect the amount of pollen produced and distributed in a specific year.   Thus, the farther north you go, the later the pollinating period and the later the allergy season.

A pollen count, which is familiar to many people from local weather reports, is a measure of how much pollen is in the air.  This count represents the concentration of all the pollen (or of one particular type, like ragweed) in the air in a certain area at a specific time. It is expressed in grains of pollen per square meter of air collected over 24 hours.  Pollen counts tend to be highest early in the morning on warm, dry, breezy days and lowest during chilly, wet periods. Although a pollen count is an approximate and fluctuating measure, it is useful as a general guide for when it is advisable to stay indoors and avoid contact with the pollen.
Most of the information was obtained courtesy: National Institute of Allergy and Infectious diseases.

April 9th, 2010 | Category: home & garden

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