Õietolm

Õietolm, the Estonian term for pollen, is the male gametophyte of seed plants, produced in the anthers of flowers and in the male cones of conifers. In flowering plants, a pollen grain contains a vegetative cell and a generative cell that divides to form two sperm cells. After pollination, pollen tubes grow through the style to deliver sperm to ovules, enabling fertilization and seed development.

The pollen wall consists of an inner intine and an outer exine made largely of sporopollenin, a highly resistant biopolymer that helps pollen survive environmental stresses and facilitates identification under microscopy. Pollen grains vary in size, shape, and surface ornamentation among species, and their unique morphology is used in palynology, the study of pollen and spores, to reconstruct vegetation and past climates.

Pollen is dispersed by different vectors. Wind-dispersed pollen (anemophilous) tends to be small, light and smooth, while insect-pollinated pollen (entomophilous) is usually larger, sticky or spiky to adhere to pollinators. Some plants rely on birds or other animals.

In humans, pollen inhalation is a common allergen source; pollen allergies cause rhinitis and asthma in sensitive individuals. Pollen also has uses in science and archaeology, where pollen grains are found in sediment layers to infer historical vegetation and climate conditions.

Overall, õietolm plays a central role in plant reproduction and ecosystem functioning, while also intersecting with human health and scientific research.