The Health of our Air Document in PDF Format Please direct all questions and comments to Barry Grace Effect of ultraviolet radiation on crops Because some UV radiation reaches the earth's surface, terrestrial plants have evolved protective mechanisms. Some produce pigments, similar to sun screen, that absorb UV radiation. The size distribution of an aerosol is closely related to its source. Coarse particles are generated mainly from mechanical processes, such as wind, whereas fine particles are produced by chemical reactions. Size distribution and chemical contents of aerosols are important factors determining global climate change and visibility.
Aerosols have a cooling effect, which offsets, in part, the warming effect of greenhouse gases.
Despite these defense mechanisms, high exposure to UV can injure cell membranes and DNA within cells. Damage to the chloroplasts reduces photosynthesis, which, in turn, can reduce plant growth. Many recent studies have evaluated the effects of increased UV on plant growth using a combination of UV filters and UV lamps to produce a range of UV intensities. Much of the research has focused on UV-B, a band of wavelengths from 290 to 315 nm. Furthermore, as observed with canola and soybean, the response to UV-B seems to vary among varieties of the same crop.