Effects of humic acid and salt stress on growth, physiological parameters and mineral substance uptake in Artemisia dracunculus L. (Tarragon)

In this study, the physiological changes in Artemisia dracunculus L. plants under salinity stress and the remediative roles of leonardite-derived liquid humic acid (HA) were investigated. Salt stress caused a significant decrease in measured growth parameters (plant height, fresh weight of leaves and stems, dry weight of leaves and stems, number of leaves and leaf area). HA had a positive effect on growth parameters at 75 mM NaCl concentration, except for leaf number, but its effect was limited at 150 mM NaCl concentration. The total amount of protein was found to be lower in the leaves of seedlings grown under the conditions of 75 and 150 mM NaCl+HA compared to plants under both salt-stressed regimes (75 and 150 mM NaCl). Peroxidase activity was increased in the 75 mM+HA group and slightly decreased in 150 mM NaCl salt-stressed samples (75 and 150 mM NaCl+HA) compared to the samples with the same salt concentrations alone. The amount of total chlorophyll and carotenoids decreased in the presence of 75 mM NaCl+HA compared to the samples of moderately stressed seedlings (75 mM NaCl), whereas the total chlorophyll and carotenoids increased in 150 mM NaCl+HA applications compared to 150 mM NaCl treatments. Analyses of nutrient elements in the above-ground and root organs of tarragon seedlings using inductively coupled plasma atomic emission spectrometry (ICP/OES) showed that in the 75 mM NaCl+HA application, the amounts of Mg, Mn, Fe and K in the above-ground organs and only Na in the root increased compared to the 75 NaCl group. In 150 mM NaCl+HA treatment, the amounts of Mg, Ca, Mn, K and Na in the above-ground organs and Ca, Mn, Fe, Cu, K and Na in the roots increased compared to the 150 mM NaCl group.