Investigation of the effects of azaleic acid on aos regulation, defence responses and cell wall resistance mechanisms under drought and salt stress in soybean (Glycine max L.) leaves

Azelaic acid (AzA) is a nine-carbon dicarboxylic acid and a signaling molecule effective in systemic acquired resistance (SAR). Since AzA is a mobile molecule that can be transported to different tissues under stress conditions; it is thought to play an important role in reducing the negative effects of stress on different tissues of the plant. This work; it was carried out to determine the effect of AzA on salt and drought stress in soybean (Glycine max L.) plant leaves. Soybean seeds were grown in soil culture in 3-5 climate chambers at 23 oC ± 1 oC, in a photoperiod of 16 hours light / 8 hours dark, under 500 μmol m2s1 light, in an environment with 60 % humidity. 15 % PEG (Polyethylene glycol 6000 MA) was used to create drought stress, NaCl (250 mM) was used to create salt stress, and two different concentrations of AzA (12, 24 ppm) were dissolved in Houglound and applied to the soil for 10 days. Harvesting was done on the 5th and 10th days. Fresh and dry weight, length, relative water content and chlorophyll amount of roots and stems were determined from the harvested samples. In addition, AOT (MDA, Proline, H2O2, O2, OH scavenging capacity), antioxidant enzyme (SOD, POX, APX, GR, GST, DHAR, MDHAR, KAT), as well as cell wall enzymes and components (PAL, PME, Lignin). Cell wall genes (XTH, EXP, WAK4) analyzes were carried out. As a result, AzA application caused improvements in physiological (chlorophyll, leaf area), biochemical (reducing MDA and ROS content), and molecular parameters in soybean plants under salt and drought stress. While AzA plays inducer role on enzyme acitivities ( SOD, APX, POX, GR, PME), it can also serve as an antioxidan without causing an increase in the cell wall related enzyme (PAL) and proline content. Beside this, it can be said that the AzA application under salt and drought stress provides stimulant effect on cell wall related gene expressions (GmXTH3, GmEXPA2, GmWAKS4).