Tez effects of salicylic acid and methyl jasmonate applications on lead stress in local Karacadağ rice (Oryza sativa L.) variety

In this thesis the effects of exogenous methyl jasmonate (MeJA) and salicylic acid (SA) on photosynthetic pigment content (chlorophyll-a, chlorophyll-b, total carotenoid), proline, malondialdehyde (MDA), total protein contents and their ability to reduce heavy metal toxicity in rice plants under lead (Pb) metal stress were investigated. In the experiment, two different concentrations of MeJA and SA were applied separately (2 and 20 mM SA; 20 and 100 µM MeJA) and in combination (2mM SA+20µM MeJA) to the plants of Hazro population of Karacadağ rice variety exposed to different concentrations of Pb (0, 100, 400 ppm) stress by foliar spraying.When the results for photosynthetic pigment contents in rice plants are evaluated; it was observed that there were significant increases in the chlorophyll-a content in Pb stress factor application (100 and 400 ppm) compared to the control group.This increase in response to Pb toxicity showed that the plant was not affected by stress in terms of chlorophyll-a content.It was determined that there was a decrease in chlorophyll-b and total carotenoid content for both concentrations of Pb compared to the control group, indicating that the plant was affected by Pb toxicity in this respect. The highest increase for all three photosynthetic pigment contents examined was obtained from plants in the group where two elicitors were applied together (2 mM SA + 20 µM MeJA). At 400 ppm Pb toxicity, groups formed by the addition of elicitors showed low MDA content, and the highest decrease was observed in 2 mM SA+20 µM MeJA treated plants with 0.537 µmol/g TA. This led to the conclusion that lipid peroxidation was prevented in this application and reduced MDA content by counteracting Pb stress. At 400 ppm Pb toxicity, the application of elicitors alone led to an increase in total phenolic content, while flavonoid content decreased. In both parameters, the combined application of elicitors at high concentrations of Pb resulted in a significant increase in the contents. In rice plants exposed to 100 ppm Pb stress factor, elicitor application affected the proline content in varying ways depending on the concentration, while there were significant increases in proline content at 400 ppm Pb stress. Among all applications, the highest increase in total protein content was obtained in the experimental group treated with 400 ppm Pb+2 mM SA+20 µM MeJA with 8.325 mmol/g TA and the highest improvement in terms of total protein content was achieved in this group. There were significant decreases in the Pb content of the elicitors applied to rice plants against the 400 ppm Pb stress factor as the concentration increased, and it was determined that MeJA was more effective than SA in counteracting Pb toxicity in these decreases.In conclusion, in this thesis, especially at high Pb concentrations (400 ppm), MeJA+SA co-application induced the toxic effect of Pb by decreasing MDA and improving photosynthetic pigments, total protein, proline and secondary metabolites and led to the best results in terms of all these properties studied. Keywords: Heavy metal, lead stress, methyl jasmonate, Oryza sativa L., salicylic acid