Pollen

Pollen consists of small spores that contain reproductive material for flowering plants. Animals, birds, insects, and the wind can move pollen from one flower to another, randomly distributing genes and allowing the plants to reproduce.

Many people experience irritating pollen allergies. Their bodies react to the pollen in the air, causing them to release chemicals called histamines. Histamines can cause itchiness, watery eyes, coughing, and congestion. Pollen allergies are commonly treated with antihistamines. However, more extreme reactions may require prescription medication.

Background

Pollen is the reproductive material created by male varieties of many plants. It takes the form of a fine powder of microspores. Pollen carries the male reproductive genes to the female reproductive parts of many plants, allowing for the genetic exchange that leads to plant reproduction. Pollen is formed in the anther, the male reproductive parts of the plant. Over time, it is delivered to the pistil, the female reproductive parts of the plant.

The stamen is the part of a plant that produces pollen. It usually features a long stalk called a filament, which is topped by a pollen storage structure called the anther. Pollen is deposited into the pistil, which is made up of the style, ovary, ovule, and stigma. The stigma is a sticky object in the center of a flower. It gathers the pollen. The style is a long stalk that supports the stigma. The ovary contains the ovules, which develop into seeds after pollination.

Overview

Cross-pollination is the transfer of pollen from one plant to another. Pollen is light enough to be carried by the wind, allowing it to spread throughout a wide area. Most grasses are pollinated by wind, as are some trees and shrubs. Plants pollinated by wind tend to have dull or no flowers. Wind pollination is much less reliable than other forms of pollination. For wind pollination to take place, random breezes must take spores of pollen from one flower to another. To compensate for such low odds of successful pollination, plants that pollinate by wind produce massive amounts of pollen.

Other plants that rely on cross-pollination use animals to distribute their pollen. These plants rely on a symbiotic relationship with nearby wildlife. Plants that form this relationship with birds tend to have large, colorful flowers. The bright flowers are easy for birds to discern from the rest of the plant.

Plants that rely on birds for pollination usually produce much nectar. Birds eat the nectar, which attracts them to the flowers. In many cases, the nectar is located at the bottom of the flower. This forces birds to push past the stamen to find the nectar, causing pollen to stick to the bird. The bird will then deposit that pollen to the next flower on which it lands.

Many plants use insects for pollination. These plants use strong scents to attract insects. Some also use brightly colored flowers, like those that use birds for pollination. These flowers often feature specialized, extra-wide petals to give insects a convenient landing place. As insects visit numerous flowers, they distribute pollen throughout them.

Cross-pollination leads to greater variation in offspring. This gives the species a greater chance at long-term survival. However, it relies on external sources for pollination. Relying on an external source of pollination makes it extremely difficult for the plants to spread to any area that lacks a prominent pollinating species of animal.

Some plants self-pollinate. When self-pollination occurs, pollen is moved from the male parts of a flower to the female parts of the same flower. Self-pollination is most commonly found in sunflowers, peas, peanuts, potatoes, and orchids. Self-pollinating plants tend to have smaller, less colorful flowers than plants that utilize cross-pollination. They also experience less genetic variation, leading to more uniform offspring. However, the process of self-pollination requires significantly less energy than cross-pollination. It also does not rely on outside sources for moving pollen, allowing plants to spread wherever their seeds land.

Pollen causes allergic reactions in many individuals. Allergic reactions are disproportionate immune system responses to a specific stimulus. Allergies can be seasonal, which means they get worse at a particular time of the year, or perennial, meaning they happen all year-round. In addition to pollen, many individuals are allergic to animal fur, dust mites, insect stings, or certain foods. Eggs, nuts, and shellfish are several common food allergies. When an individual is exposed to something to which he or she is allergic, the body releases histamines.

Histamines are chemicals that help force a foreign substance out of the body. They are created by the immune system and then stored in mast cells. When an individual's body begins to release histamines, he or she may begin to cough, sneeze, itch, or experience watery eyes. In extremely severe cases, the body goes into anaphylaxis.

Anaphylaxis is an allergic reaction that begins with mild allergy symptoms. However, it quickly advances to feature hives, swollen lips, a swollen tongue, coughing, wheezing, itching, a swollen throat, and trouble swallowing. Anaphylaxis requires immediate medical attention. Should the reaction remain untreated, anaphylaxis can be fatal.

Allergies are commonly treated with antihistamines. Antihistamines suppress the body's reaction to histamines, reducing the symptoms of an allergy. Histamines also help keep the body awake and alert, while antihistamines can sometimes induce drowsiness when ingested. Extreme reactions, such as anaphylaxis, are often treated with epinephrine injections.

Pollen allergies are often caused by plants that pollinate by wind. Pollen produced by ragweed, grasses, and oak trees are all common allergy triggers. Symptoms of pollen allergies include itchy, watery eyes; sneezing; congestion; itchy throat, and coughing.

Bibliography

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