Exposure to the types of radiation encountered during space flight such as solar protons and helium ions beyond Earth's magnetosphere, galactic cosmic ray HZE particles (protons and particles of high atomic number and high energy), and high proton fluxes from solar proton events may cause a number of health-related problems such as the increased risk of cancer induction in astronauts (Kennedy and Todd, 2003; National Research Council, 1996). Recent studies have shown that flavonoid compounds found in many plant species have biological activities that may mitigate oxidative damage resulting from ionizing radiation-induced damage (Arora et al., 2005; Rabin et al., 2005). It is believed that a diet rich in bioactive phytochemicals could be an effective countermeasure to both reduce the effective dose of oxidative compounds and events and induce in situ repair of oxidative damage in tissue (Stutte, 1999; Venkatachalam and Chattopadhyay, 2005; Wheeler et al., 2002).
There is significant literature that the use of naturally occurring antioxidants can mitigate the effect of radiation damage and be an effective countermeasure to mitigate the effect of, and enhance healing from, oxidative damage (Bhatia and Jain, 2004; Rabin et al., 2005). High antioxidant capacity has been attributed to members of the flavonoid family, particularly anthocyanins. Purified anthocyanins have been found to rank highly among other phenolic antioxidants, and their capacities to absorb oxygen radicals is up to four times greater than those of ascorbic acid and vitamin E (Gould, 2004).
In addition to their health benefits, anthocyanins are a key indicator of commercial quality for many fruits, vegetables, and ornamentals. As such, treatments that can increase the accumulation of anthocyanins are of great interest and importance in agriculture. Treatments that increase the production of anthocyanin include a number of environmental stressors such as high irradiance, temperature extremes, ultraviolet radiation, mineral imbalances, water stress, mechanical injury, and pathogen attack (Gould, 2004).
A promising electric light source for controlled-environment plant growth is light-emitting diodes (LEDs), which are solid-state, durable, lightweight, extremely long-lived, and come in selectable narrow-waveband emissions that can be matched to the absorption spectra of plant pigments (Goins et al., 1997; Kim et al., 2005).
The objective of these experiments was to test the hypothesis that high anthocyanin production and antioxidant potential could be obtained when growing red leaf lettuce under LEDs.
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