Time course of physiological and biochemical responses of Thymus vulgaris to short-term salinity stress in hydroponics

The present study aimed to investigate the physiochemical responses of Thymus vulgaris L. to salinity stress and was arranged in a two-factorial experiment based on a completely randomized design (CRD) with three replications under floating hydroponic conditions. The effect of salinity stress at three levels of 0, 100, and 200 mM NaCl for seven different time courses of 0, 6, 12, 24, 48, 72, 96, and 120 h on 3 months garden thyme plant (4 months after seed cultivation and 3 months after transplanting in hydroponic system) was investigated. The results showed that different concentrations of NaCl and different times of salinity stress had no significant effect on the fresh mass, while photosynthetic pigment content and DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical scavenging activity were significantly decreased under high concentrations of sodium chloride and 72-120 h after salt stresses. In addition, the increase of salinity stress (100 and 200 mM) in 72-120 h treatment significantly increased compatible osmolytes, such as proline content. On the other hand, the activity of non-enzymatic antioxidants, such as phenolics and flavonoids under salt stress treatment with concentrations of 100 and 200 mM sodium chloride in the floating hydroponic system during 72-120 h showed significant increases. In general, it can be concluded that high concentrations of sodium chloride in floating hydroponic systems can cause significant adverse effects on the physical and biochemical properties of the garden thyme plant.