Journal of Ecosystem & Ecography
Open Access

Abstract

The Ultraviolet (UV) radiation is defined as that portion of the electromagnetic spectrum between X rays and visible light, i.e., between 40 and 400 nm (30?3 eV). The sun is our primary natural source of UV radiation. UVB is typically the most destructive form of UV radiation because it has enough energy to cause photochemical damage to cellular DNA, yet not enough to be completely absorbed by the atmosphere (Zeman Gary, 2011). The use and benefits of radiation for producing new varieties of cereals, oilseeds crops, pulses, fruits and flowers that have added billion of dollars to the agriculture and provided food for millions in the country. The results with respect to radiation- induced mutagenesis in the case of different crops such as potato, sugarcane, sweet potato, garlic, mint, chrysanthemum, orchids, banana, etc. Near about 3000 mutagen varieties have been released so far and that more than 60% were after 1985 in the era of biotechnology in plant breeding. There are 2275 such varieties as many as 1072, 66 and 34 are in cereals, vegetables and legumes, respectively. In terms of percentage China, India, USSR, Netherlands, USA and Japan account for 26.8, 11.5, 9.3, 7.8, 5.7 and 5.3% of mutagen varieties. Such varieties are 2, 3 and 25% in fruits, vegetables and ornamentals, respectively. Giving examples of Novaria bananas as resistant to new race of Fusarium, black segatoka and yellow segatoka, and verticillium-wilt tolerant varieties of mint. The wider application of radiation technology in agriculture is the economic aspects of mutagen varieties released in Japanese pear, peppermint and chrysanthemum touch 30 million, 200 million and 120 million dollars commerce, radiation- induced mutation holds promise for developing dwarf indoor shrubs (Ahluwalia, B.S, 2009) The effect of UV-B enhancement on plants include reduction in yield and quality, alteration in species competition, decrease in photosynthetic activity, susceptibility to disease and changes in plant structure and pigmentation. This issue is complicated further by reports of equally large response difference among cultivars of a species. About two-thirds of more than 300 species and cultivars tested appear to be susceptible to damage from increase UV-B radiation. The importance of solar angle, atmospheric turbidity, elevation above the sea level, cloud cover, total atmospheric ozone column, and UV albedo of the earth?s surface with respect to the total UV irradiation intensity and wavelength composition should be considered in UV radiation natural environments. Though not all the respondents demonstrated as the result of UV radiation are considered as damaging or disadvantageous for the plant the majority of evidence indicate the UV irradiation is usually detrimental, particularly UV-B irradiation (Caldwell, 1971). In this section a summary of the UV-B effects on crop from the literature will be presented. The growth of many plant species is reduced by enhanced levels of UV-B radiation (Teramura et al., 1989). In agriculture, reduction in stratospheric ozone will require the use of UV-B tolerant cultivars and the development of new ones. Scientific evidence indicates that there will be an adverse effect on crops, but the magnitude of these effects cannot be estimated given the current state of knowledge (UNEP, 1994; Tevini, 1993). Most of the plants have UV shielding, but not always sufficient for complete protection. Only a small proportion of the UV-B radiation striking a leaf penetrates into the inner tissues. When exposed to enhanced UV-B radiation, many species of plants can increase the UV-absorbing pigments in their outer leaf tissues. Other adaptations may include increased thickness of leaves that reduces the proportion of inner tissues exposed to UV-B radiation and changes in the protecting waxy layer of the leaves (Anonyms, 2006). The consequences of increase in UV-B irradiation on the growth, productivity of crops in developing nations are largely ignored. UV-B radiation is reported to be harmful to plants in many ways, and the reduction in their yield by UV-B can have adverse consequences in developing countries. One way plants can protect themselves against UV-B light is by induction of DNA photolyase which can repair the UV-B damaged DNA.

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