Ultraviolet radiation effect on photosynthetic pigments, biochemical attributes, antioxidant enzyme activity and hormonal contents of wheat

As a result of contamination with man-made chlorofluorocarbons, the stratospheric ozone layer is being depleted which results of that enhanced solar ultraviolet-B (UV-B) irradiance rising an adverse impact on living organisms. However, under a nature condition, it is very difficult to simulate UVB irradiance spectral changes. Present investigation was aimed to determine the effect of ultraviolet radiation on photosynthetic pigments, biochemical attributes, antioxidant enzyme activities and hormonal contents in wheat. The UV-B was applied for 1, 2 and 3 h to 25-day old plants at vegetative stage. The results indicated that increased UV-B radiation produced negative effects on stem height, dry weight, leaf area, spike length, number of grain per spike and 100 grain weight, while leaf thickness was increased with enhancing duration of UV-B treatment. The supplementary UV-B radiation significantly increased sugar, protein and proline content in wheat leaves. Concomitantly, transcripts of key enzymes of the antioxidative defense system, such as superoxide dismutase (SOD), peroxidases (POD) and ascorbate peroxidase (APOX) were also enhanced by UV-B radiation while, the chlorophyll and carotenoid contents of leaves were decreased as compared to untreated plants. Furthermore, the use of UV-B augmented the ABA contents but decreased the IAA and GA contents. These results suggest that wheat varieties with resistance against UV-B radiation were found sensitive by possible negative effect of additional UV-B radiation on the photosynthetic pigments and also on IAA and GA contents, while an increase was found in UV-absorbing compound, antioxidant enzymes and ABA contents.