Effect of UV-B radiation on growth and development on in vitro grown salvia limbata c.a.mey

In this thesis, the responses of Salvia limbata cultures in the early vegetative growth (EVB) and late vegetative growth (GVB) stages to UV-B applications were investigated. In this context, after cultures at two different developmental stages were exposed to UV-B radiation for different durations (15, 30, 45 and 60 min), shoot number, stem length, total phenolic and flavonoid content and total antioxidant activity data of the control and all treatment groups were evaluated. Growth responses, antioxidant activity potential, total phenolic and flavonoid content of the application groups were found to be variable depending on the developmental stage and application period. When the treatment groups were compared with the control in terms of shoot number and stem length, the best result was obtained from the 15 min UV-B application period in the EVB phase. In this group, the number of shoots per explant (4.7000±1.15) and the data on stem length (7.5750±0.43 cm) were found to be statistically significant. The fact that the morphological development in the shoots was similar to the controls and the shoot number and stem length results were approximately 2.5 times higher than the controls explains the positive effect of the 15-min application period on growth and development. On the contrary, 30 min. UV-B caused slight color change in shoots, leaf blade enlargement, stem thickening and most importantly a significant decrease in the number of shoots (2.3000±0.21). Despite this decrease, it was recorded that the number of shoots in this group was higher than the control group (1.9000±0.160). At the end of 45 and 60 min UV-B applications, the number of shoots in both groups was statistically similar, but unlike the other groups, these application times caused yellowing of the leaves, necrotic spots, increase in leaf thickness and shortening of leaf petioles. In all application groups of GVB stage, data on stem length showed statistically similarity. Although 15-min applied in the GVB phase increased the number of shoots (2,8500±0,20) and stem length (4,4350±0,13 cm.), it was not found to be as efficient as the results obtained for the same time of the EVB stage. At the same time, 15 min. UV-B applied at the GVB stage caused shrinkage and slight color change in the leaves. Compared to the control group, it was determined that there was an approximately 1.8-fold increase in the number of shoots per explant with 30 min application and an approximately 2-fold increase with 45 min application in the GVB stage. Unlike other application times, 60 min UV-B caused shrinkage and browning of leaves, shortening of leaf petioles and formation of intense basal callus. In this thesis study, it was determined that the total phenolic substance accumulation in the extracts of the application groups changed depending on the UV-B exposure time and developmental stage. In the EVB phase, a decrease in the total phenolic substance content of the extracts was observed due to the extension of the application time, except for the 15 min UV-B group. In the GVB phase, the increase in the total phenolic substance amount due to the extension of time was found to be lower than the control group, except for the 60 min application (413.73±6.14 µg GAEs/mg extract). The results of this study show that the amount of total flavonoids in the extracts of cultures at EVB and GVB stages changed depending on the application time. Compared to the control group (20.36±1.48 µg QEs/mg extract), the best data regarding this parameter were obtained from the 15 and 30 min application groups (respectively, 99.63±2.05; 83.42-1.79 µg QEs/mg extract) in the EVB stage. Although there was a significant decrease in the total flavonoid amount due to the extension of the application time (45 to 60 min. UV-B), the results obtained were found to be higher than the controls. In the GVB phase, it was determined that the total flavonoid accumulation in the extracts increased regularly with the extension of the application period. It was determined that the maximum flavonoid accumulation in this developmental stage occurred in the 60 min time (49.18±1.74 µg QEs/mg extract), and the minimum accumulation occurred in the 15 min time (22.61±1.26 µg QEs/mg extract). In this thesis, the total antioxidant activity potential in extracts of the application groups was investigated using the DPPH test method. As a result of the analyses carried out for this purpose, the increase detected in total antioxidant activity data as the concentration of control and positive controls increased was also recorded in all application groups of EVB and GVB stages. The analysis results show that the total antioxidant activity potential of the 15-min application group in the EVB phase is close to the control group. However, it was noted that the antioxidant activity potential was more active in the 100, 150 and 200 µg/ml concentration extracts of the 60 min UV-B group in the GVB phase compared to the control extracts. As a result, it was determined that antioxidant activity data were close to or higher than the control group in some concentrations of the extracts of the application groups.