Pollen

Microscopic particles produced by plants for reproduction

Pollen

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Microscopic view of pollen grains.

Pollen is a fine to coarse powdery substance comprising pollen grains which are male microgametophytes of seed plants, responsible for the production of male gametes (sperm cells). Each pollen grain contains a vegetative cell, which produces the pollen tube, and a generative cell, which divides to form the sperm cells. Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the female cone of coniferous plants.

Structure and Function

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Diagram of a pollen grain structure.

The structure of pollen grains varies among species, but they generally consist of three main parts: the exine, intine, and the cytoplasm. The exine is the outer layer, composed of sporopollenin, which is highly resistant to degradation. The intine is the inner layer, made of cellulose and pectin. Inside the pollen grain is the cytoplasm, which contains the vegetative and generative cells.

Pollen serves a crucial role in the reproductive cycle of seed plants. It is involved in the process of pollination, where pollen is transferred from the male anther of a flower to the female stigma. This can occur through various means, including wind, water, and animal pollinators such as bees, birds, and bats.

Types of Pollen

Pollen can be classified based on the method of pollination:

• Anemophilous pollen: This type is adapted for wind pollination. It is typically small, light, and produced in large quantities to increase the chances of successful pollination.
• Entomophilous pollen: Adapted for insect pollination, this type is often sticky or spiky to adhere to the bodies of insects.
• Hydrophilous pollen: Found in aquatic plants, this type is adapted for water pollination.

Allergies and Health Effects

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Pollen can cause allergic reactions in sensitive individuals.

Pollen is a common allergen and can cause allergic rhinitis, commonly known as hay fever, in sensitive individuals. Symptoms include sneezing, runny nose, itchy eyes, and congestion. Pollen allergies are typically seasonal, coinciding with the flowering periods of plants.

Ecological Importance

Pollen is a vital component of ecosystems, serving as a primary food source for many insects, including bees and butterflies. It is also used by some birds and mammals. The transfer of pollen is essential for the fertilization of plants, leading to the production of seeds and fruits, which are crucial for the survival of many species.

Related pages

• Pollination
• Allergic rhinitis
• Sporopollenin
• Seed plant
• Anther
• Stigma (botany)