The effect of pretreatment of seeds of Thymus daenensis by peppermint and seaweed extracts on germination and seedling growth under salinity stress conditions

The percentage and rate of seed germination are critical factors leading to high yield in agriculture, but it has a diminishing effect on environmental stress. Seed pretreatment is one of the ways to increase the strength and velocity of seed germination to deal with salt stress. The purpose of this study was to investigate the effect of seed pretreatment by peppermint (0.5, 1, and 2%) and seaweed extract (0.5, 1, and 2%) with control on the growth and biochemical traits of Thymus daenensis seedling under salinity stress (0, 50, 100, and 150 mM NaCl) conditions. This experiment was conducted as a factorial as a completely randomized design in four replications at the seedling growth stage. The results showed that seed pretreatment with peppermint and seaweed extract increased the percentage, velocity, and time of germination as well as the number of germinated seeds, in the absence of salinity stress. In seedling growth characteristics, although they were better in the absence of salinity stress, the pretreatment of the seeds significantly reduced the effects of salinity stress compared to the control conditions. The highest amount of chlorophyll in this condition was obtained in seeds treated with 2% seaweed extract. The highest activity of catalase enzyme and polyphenol oxidase enzyme was obtained in 100 and 150 mM salinity stress conditions and seeds treated with 1 and 2% seaweed extract, respectively. Salinity stress had caused a decrease in growth parameters, but seaweed extract pretreatment had improved the conditions.