Abstract: Cryptogam means nonseedbearing plant; it is a constituent part of biological soil crust (BSC)——the main characteristic on the surface in arid and semiarid regions, which plays a vital role in ecosystem. According to diversity and difference of the dominated species in BSC, the cryptogam is mainly distinguished into three basic types: algae, moss and lichen. Because of their simple morphological and anatomical structures, the cryptogam is easily influenced by environments and often used as an indicator of environmental variations. So the response and adaptability of cryptogam to environmental factors is of great importance in the stability of the whole ecosystem. The increase in the intensity of ultraviolet radiation (mainly UV-B) invades land due to stratospheric ozone depletion resulted from human activities, made a series of impacts on terrestrial beings, it also effects the composition, structure and function of cryptogam to an even greater degree. Many studies have shown that enhanced UV-B radiation intensity made effects on growth development, photosynthesis, metabolism, antioxidant system and cell membrane of plants. Therefore, studies related to the effects of enhanced UV-B radiation on cryptogam has become a growing tendency and one of the hot spots in UV-B radiation research. The Cryptogam has very important ecovalue in arid and semiarid regions, which is the dominant component of BSC in desert region, It is also one of the evaluating index for ecosystem stability and restoration of degraded ecosystem. Now there are many reports about the researches concerned with the effects of UV-B on cryptogam and as a result the paper introduces the concerned domestic and international researches in this field, which include effects of cryptogam to enhanced UV-B radiation on biomass, photosynthetic ability, photosynthetic pigments, antioxidant enzymes activity, watersoluble protein content, DNA damage, fatty acids and so on. In order to understand the effects of UV-B radiation on the physiological properties of cryptogam, based on different kinds of cryptogam, the research progresses were systematically reviewed of the responsive and adaptive mechanism of cryptogam to enhanced UV-B radiation, and further some deficiencies were proposed in current studies and a prospect set out for the future researches to enhance the understanding on responsive and adaptative mechanism of cryptogam to increased UV-B radiation in arid and semiarid regions of China. The conclusions are as follows: the effects of UV-B radiation are closely related to plant species, UV-B radiation and treatment time. It is significant to study enhanced UV-B radiation on cryptogam, which could be helpful to deepen our understanding on cryptogam and to promote the researches of its ecological functions and provide the theory basis for accurately predicating irthe effects in the arid and semiarid areas in China under global elevated UV-B radiation.

Key words: UV-B, Algae, Lichen, protective pigments, adaptive mechanism