NASA SOHO Mission,Yohkoh
science team
Ecological impacts of
UV-B radiation
Organismal effects and responses
Plants
Most research on the responses of plants to UV-B to date has been conducted on phytoplankton and agricultural plants. Less is known about responses of plants of forest, grassland, heathland, tundra, savannah, etc. ecosystems. Plants exposed to UV-B exhibit physiological, biochemical, morphological, and anatomical changes (Wetzel 2001) with the level of exposure closely related to the response. Dose of UV-B, the ability of the plant to escape from further exposure and allow repair, life cycle, and other environmental conditions are important factors that complicate the effects of UV-B on plants.Dose
High levels of UV-B cause DNA damage but most plants also possess repair mechanisms (Frohnmeyer and Staiger 2003). Meanwhile low doses of UV-B have been observed to stimulate production of protective and photomorphogenic responses such as production of UV-B absorbing phenolic compounds(Frohnmeyer and Staiger 2003). In potato plants, UV-B exposure activated defense mechanisms such as decreased plant height and leaf area and increased leaf thickness, as well as increases in flavenoid levels, and synthesis of a new type of protein (Santos et al. 2004). Similarly, Coleman and Day (2004) found that >70% of ambient UV-B induced production of soluble UV-B absorbing compounds in sorghum and cotton plants.Mobility
Since some phytoplankton can move in the water column, they are thought to be able to limit their exposure to UV-B as compared to more sessile plants. On the other hand, reduced exposure to UV-B by swimming to deeper depths also means that the phytoplankton would be exposed to less light for photosynthesis and thus, their productivity would decrease. Phytoplankton community diversity has been observed to decrease in response to elevated UV-B in montane lakes (Tank and Schindler 2004), and phytoplankton primary production has been observed to decrease in marine environments (Karentz and Bosch 2001), in response to UV-B .Life stage
South African Mediterranean-climate legumes (Podalyria calyptrata) were shown to be more susceptible to UV-B damage during a particular stage. In a study done by Musil et al. (2003), supplements of nitrate caused the plants to become more metabolically active and thus, more susceptible to photosynthetic inhibition by UV-B.Environmental conditions
Lichens (algal and fungal symbionts were observed to be more susceptible to UV-B damage during periods of desiccation despite that they are normally able to withstand UV-B exposure (Nybakken et al. 2004). Dessication of lichen is a response to severe temperatures or drought. Additionally, Gleason and Wellington (1993) suggest that periods of coral bleaching (dissociation of endosymbiotic algae) in the Caribbean , not attributable to temperature alone, may be due to calm clear waters and associated increased UV-B exposure. They observed that regardless of high water temperature, bleaching is induced by short-term increases in UV-B.