Ultraviolet (UV) light makes up a part of light. The human eye cannot see ultraviolet light as it is shorter than visible light. This ultraviolet light can be harmful to animals when they are exposed to it over a long period of time, according to the Ozone Hole. Fortunately, the clouds and the ozone are capable of deflecting enough of the UV radiation to where it is not too harmful.
When plants are hit with ultraviolet light, this event triggers the plant's defense mechanisms. The plant then becomes more resistant to insect attacks as it releases 15 defense proteins. The ultraviolet light also affects message pathways that impact plant development, growth and metabolism, according to Washington State University. The ultraviolet light tricks the plant into thinking that it is wounded, which occurs when the plant is being feed on by insects. However, the ultraviolet radiation does not help the plant compete with weeds, according to Plant Cell.
UV rays can also have a harmful effect on plants. UV radiation reduces production rates of crops, which reduces the worldwide availability of food, according to the Ozone Hole.
Ultraviolet light can do damage to the DNA of the plant. These changes in DNA can have very random effects, causing some species of plants to mutate, according to Plant Cell. Also, the cells can die as a result of the DNA damage. To prevent these events, the DNA must be repaired before the DNA is replicated. The DNA is repaired through photoreactivation, excision repair or recombination repair.
Ultraviolet light can also do damage to the plant's physiological processes. UV-B radiation reduces the amount of pollen that the plant is able to release, according to Plant Cell. The UV-B also reduces the biomass of the plant. These plants also experience epidermal deformation and cuticular wax composition. These effects not only come from the DNA damage but also from protein destruction, hormone inactivation and signal transduction, which is a conveyance of signals, through phytochrome. These changes can cause damage to the plant tissue, which can eventually cause plant death.
Some kinds of ultraviolet light can cause more damage to plants than others. UV-C protons are very energetic and are very highly absorbed by the plants, so they can do a lot of damage very quickly, according to Plant Cell. Because of the speed in which the UV-C protons affect the plants, they are usually the rays used to study the affects of UV light on plants.