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Item Laser induced fluorescence for stress studies on maize plants under control conditions(University of Namibia, 2015) Van Kent, Alfred A.The growth of plants is affected by several environmental parameters of which light (particularly UV) is the most important. It is a well established fact that similar plants grow differently in different regions, due to the fact that the local environmental conditions vary from place to place. Stratospheric ozone depletion has caused an increase in the amount of ultraviolet-A (UV-A) and ultraviolet-B (UV-B) radiation reaching the earth’s surface. In Namibia, excessive ultraviolet (UV) radiation is one of the main factors that adversely effects the growth of vegetation and therefore the study of its influence on the growth of plants is very vital. For this study, an advanced technique of Laser-Induced Fluorescence (LIF) is used. When plant leaves are irradiated by ultraviolet (UV) radiation, fluorescence spectrum shows four peaks centered at wavelengths of 450nm, 530nm, 685nm and. The ratio of blue (450nm) to red (730nm) fluorescence differs from plant to plant and is considered a stress indicator. For laboratory measurement of fluorescence spectra from the leaves of maize plants grown under controlled conditions such as humidity, temperature, water and mineral stresses, and exposed to UV-A and UV-B radiation over different timelines are used. The emission spectrum of the third leaf from the bottom side of each maize seedling were obtained using a AvaLight- D(H)S Deuterium-Halogen light sources (337 nm), which was connected to Ava Spec-2048 Fiber Optic Spectrometer and a computer for displaying the results in a graph format. In this study, the intensity ratios of these peaks as 𝐅𝟒𝟏𝟎𝐅𝟒𝟑𝟎 , 𝐅𝟒𝟏𝟎𝐅𝟓𝟓𝟎, and 𝐅𝟓𝟓𝟎𝐅𝟓𝟗𝟎 corresponding to blue to green, blue to red, and chlorophyll fluorescence were calculated and analyzed. This study focused on maize plants due to socio-economic importance of maize in Namibia. The ratio 𝐹410𝐹430 , that is blue to green, has decreased from 0.4 to 0.2, that is a 50% decrease, while the ratio 𝐹410𝐹550, that is blue to red, increase from 0.2 to 0.4, which is an increase of 100%. On the other hand, it was found that the ratio 𝐹550𝐹590 , the chlorophyll flurescence, has decreased from 2.9 to 1.6, which is a decrease of 44.8%. The decease in the ratio 𝐹550𝐹590 , the chlorophyll flurescence is due to the reduction in photosynthesis activity and hence the health status of plants, whereas the decrease in the ratio F410F430 (blue to green fluorescence) reflects the chlorophyll and carotenoid pigmentation in green leaves. The increase in the ratio of F410F550 (blue to red) with the increase of UV-A and UV-B radiation, could be due to the reabsorbtion on the red light in the the inner leaf with high concentrations of flavonoids and anthocynanins. Furthermore, it was found that UV-B was more destructive than UV-A. From measurements taken of the growth parameters, such as number of leaves, width of the leave, diameter of the stem and height of seedling, the following were observed. When exposed to UV–A, the width of the leave reduces from 1.7 to 0.7 (58%), the diameter of the stem reduced from 0.4 to 0.1 (75%), and the height of the seedling from 41 to 19 (53%). In this study it is thus observed that UV and in particular UV-B has significant impacts on the total biomass and the growth of plants. This is in agreement with other reports that plants are more susceptible to long-wave UV-B irradiation and that this difference is more apparent from the changes in total area of leaves and dry mass of shoots, rather than from the parameters of chlorophyll fluorescence and net photosynthetic rate. It is recommended that the continued advancement of laser research and the further development of laser remote sensing techniques for atmospheric, environmental and further vegetative studies be actively promoted and motivated.