The Protection Research Of Natural Aloe Extracts On Wheat Under UV-B Stress

The ozone in the stratosphere of the earth can effectively absorb the solar UV radiation,which protect the life on the earth from harm of ultraviolet radiation.However,with the rapid development of modern industry,the concentration of HCFC compounds is increasing year by year. When HCFC compounds research the top of stratosphere,the compounds would be degraded and give off chlorine atoms,and it would catalyze ozone molecule into oxygen molecule.Then the ozone is consumed,making ozone layer in the stratosphere thinning,and which lead to the enhancement of solar UV radiation reaching the earth surface. Then it does harm to the life on the earth various extents. A large number of studies have been reported that the damage of enhanced UV radiation on plants at present. However, there is few research materials about how to prevent or reduce the harm of enhanced radiation to the crops in field conditions.In this paper, the effects on morphology and physiological and biochemical indexes of wheat sprayed by natural aloe extract under artificially enhanced ultraviolet radiation condition were investigated by means of plant anatomy and phytochemistry. The purpose of this study is to explore the degree of damage on wheat under enhanced UV radiation and the protection of natural aloe extracts on wheat under UV stress. The results showed that:1.The epidermis of wheat leaf consist of one layer cells,which align along the long axis of leaf ,and it contains long and short two types cells.The long cells are rectangle.The long diameter has the same direction with the long axis of leaf. The outside wall is keratinocyted with silicon; The short cells is square or slightly compressed, inserted in the long cells and they contains silicon cells and bolt qualitative cells.There are bulliform cell in the upper epidermis.Stomata arrange longitudinally in the both upper and lower epidermal layers.The guard cells of stomata are square-shaped.In the natural condition,the stomata,long and short cells are all in the same plane.But in the conditions of enhancing UV radiation,the stomata subsidence is obvious and cuticle increases.This is a kind of structural adaptation to reduce moisture loss.Because the aloe polysaccharide has moisturizing function. When spraying the aloe extract on the wheat surface,the stomata subsidence of leaf ease sharply. 2.Applying the method of cell segregation and microscopic inspection, the mesophyll cells of wheat under UV stress were observed. We found that most mesophyll cells of wheat are parenchyma cells with many rings and chloroplasts. The cells of CK group have a few more rings(6-8 rings) and larger chloroplast. The ring number(2-4 rings) of mesophyll cells of UV group decreased sharply,and the cells became shorter and their chloroplasts became smaller. It shows that enhancing UV radiation is not good for growth and development of mesophyll cells of wheat. The structure of mesophyll cells sprayed aloe extract was similar to that of under natural light.3.The determination results of physiological and biochemical indexes showed that under the conditions of artificially enhanced UV radiation ,the chlorophyll content and biomass of UV group which were not sprayed with aloe extract , significantly decreased compared with CK group. While some indicators such as POD activity, SOD activity, relative conductivity and MDA content increased at different level. Every index of the wheat under enhanced UV radiation but sprayed with 3 different concentration of aloe extracts tended to that of the CK group, in which the protection effect of the concentration with 0.01g/mL was better. The total amount of chlorophyll and biomass of wheat in T2 group are higher than that of UV group by 19.21% and 9.74%.The relative conductivity, MDA content and POD activity decreased respectively by 21.16%, 21.98% and 11.53% compared with UV group.4.Analyzing the results of plant anatomy and physiological and biochemical research comprehensively, it proved that natural aloe extract could protect plant from UV damage.Plant chemical analysis shows that aloe extract mainly contains anthraquinones and aloe polysaccharide. With the fluorescence microscope observing aloe anthraquinones, it issued orange fluorescence by purple or blue light irradiation.Accordingly,the author analyzed that the wheat surface was sprayed by Aloe anthraquinone which absorbed UV light,and making the electronic jumping from ground state to excited state. When the electronic goes back to the ground state,it would release the absorbed light with the form of orange fluorescence whose weak radiating capacities. Thereby it can protect plant from the harm of UV radiation.So spraying natural aloe extract on the wheat surface is an effective measure to defense UV radiation harm.