The effect of plant growth promoting bacteria application on physiological parameters, volatile components and nutrient elements in mint grown under salt stress

In this thesis study, Bacillus amyloliquefaciens (Ba) was applied to Mentha piperita L. seedlings grown for six weeks at various salt levels (0, 50, 75, and 100 mM). The study was carried out with a total of eight groups, with 24 seedlings (8 seedlings and 3 replicates) in each group. At the end of six weeks, some physiological parameters, plant nutrients, and volatile component contents were examined in the seedlings. The negative effect of salinity was observed in almost all parameters (except water content). There was a 19% decrease in root length between the control with the highest value (17.3 cm) and the lowest value with 100 mM NaCl (14.0 cm). The highest and lowest values in stem elongation, root width, fresh weight, and dry weight parameters were determined in the same group. Accordingly, the highest values were detected in the control, and the lowest values were detected in Ba+100 mM NaCl. When the highest and lowest values were compared, 50% reduction in stem elongation, 38% in root width, 76% in fresh weight and 84% in dry weight were observed. Unlike other parameters, the lowest value in water content was found in the control and the highest value was found in Ba+100 mM NaCl and the increase was approximately 10%. The negative effect of salt was intense in physiological parameters, but Ba application did not show the expected promoter effect on the groups. When all groups of plant nutrients are evaluated, Ba had positive effects on Zn, Mn, Cu, and Na values compared to the control, but it could not show its effect on B, Fe, K, P, Mg, and Ca. In volatile components, limonene was detected as the major component in all groups. As a result of the evaluation made on limonene, the highest rate was found in the control, and the lowest rate was found in 100 mM NaCl. Salt-dependent inhibition was 73% between the groups with the highest and lowest limonene. While the negative effects of salt on almost all parameters were intensely observed, the promoter effects of Ba were not very evident.