The late summer and fall pollen allergies are usually caused by ragweed (Ambrosia aratemisiifolia and Ambrosia trifida), a widespread anemophilous plant.
Arizona was once regarded as a haven for people with pollen allergies, since ragweed does not grow in the desert.
The transfer of pollen grains to the female reproductive structure (pistil in angiosperms) is called pollination.
Germination of the microspore begins before it leaves the pollen-sac.
Each pollen grain contains one or two generative cells (the male gametes) and a vegetative cell.
Anemophilous plants typically produce great quantities of very lightweight pollen grains, often with air-sacs, and generally have inconspicuous flowers.
Once the pollen grains have been identified, they can be plotted on a pollen diagram, which is then used for interpretation.
Anemophilous spring blooming plants such as oak (Quercus), birch (Betula), hickory (Carya), pecan (Carya illinoinsis), and early summer grasses may also induce pollen allergies.
Pollen diagrams are useful in giving evidence of past human activity (anthropogenic impact), vegetation history, and climatic history.
The male cells are carried to their destination in the tip of the pollen tube.
Some windblown pollen is likely to be inadvertently collected by bees, since they bear a static charge.
Entomophilous (literally insect-loving) plants produce pollen that is relatively heavy, sticky, and protein-rich, for dispersal by insect pollinators attracted to their flowers.
The study of pollen is called palynology and is highly useful in paleontology, paleoclimatology, paleobotany, archeology, and forensics.
Bees will collect pollen from some grasses and grains when they cannot find pollen with more nutritional value; however, anemophilous plants such as grasses generally have very low real value to bees.
Pollen reflects the male aspect of the harmonized positivity and negativity that are fundamental attributes of nature (protons and electrons in atoms, positive and negative ions in molecules, male and female in animals, etc.).
Pollen is produced in the microsporangium (contained in the anther of an angiosperm flower or male cone of a coniferous plant).
Pollen grains come in a wide variety of shapes, sizes, and surface markings characteristic of the species (see photomicrograph at right).
Pollen, or flower sperm, is a fine to coarse powder consisting of microgametophytes (pollen grains), which carry the male gametes of seed plants (angiosperms and gymnosperms).
Many trees and flowering plants are a good source of pollen for honeybees.
Pollen grains of pines, firs, and spruces are winged.
Breathing air containing these pollen grains brings them into contact with the nasal passages.
Palynology is the study of pollen and spores, both living and in fossil form.
Ragweed and pine pollen can settle on leaves and other flowers, to add to the total quantity of pollen that are found upon analysis of gathered pollen.
Except in the case of some submerged aquatic plants, the mature pollen-grain has a double wall, a thin delicate wall of unaltered cellulose (the endospore or intine) and a tough outer cuticularized exospore or exine.
Pollen is sold as a nutritional supplement, marketed as "bee pollen" (even though it is, of course, from flowers).
The smallest pollen grain, that of the Forget-me-not plant (Myosotis sp.