the effect of seed priming on alpha amylase activity, starch, proline and soluble sugars total levels of milk thistle seeds under saline stress condition

Introduction: nowadays, the use of medicinal plants has increased. milk thistle (silybum marianum) is one of the most important chemotypes specific medicinal plants of asteracea family whose seeds effective substance is used in the production of medicines for liver diseasesand and biliary tract (migahid et al., 2019; liava et al., 2023). the seeds of this plant consist of silymarin (a flavonolignan complex) and 20–35% fatty acids, including linoleic acid. silymarin is a complex mixture of polyphenolic molecules, including seven closely related flavonolignans (silybin a, silybin b, isosilybin a, isosilybin b, silychristin, isosilychristin, silydianin) and one flavonoid (taxifolin).(nasiri et al., 2014) seed priming is a pre-sowing treatment in different ways so as to cause early germination, increasing of competitive ability, tolerate drought periods and salinity condition and obtain better seed vigor (ebrahimi et al., 2020). the purpose of this study is to investigate the effect of seed priming on some physiological characteristics of two genotypes of majar and amol under salinity. materials and methods: this study was conducted to evaluate the physiological and biochemical mechanisms of seed priming treatment which improved the quality of milk thistle (silybum marianum) seeds. the experiment was conducted in agricultural biotechnology research institute of iran (abrii) and its experimental design was arranged in a completely randomized design with three replications and four factors. the factors were first: genotype (amol and majar), second: primed (kno3 -2 bar) and non-primed seeds, third: salinity (150 mm) and controlled (non-salinity) conditions and the fourth: time of sampling in 24 and 96 hours after sowing. biochemical indices that were analyzed in this step included alpha amylase activity, proline (bates, 1973), starch (the modified method of schlegle et al, 1986) and soluble sugares (aoac,1995) levels using advanced analyzing methods and spectrophotometer varian cary 300. results and discussion: priming had a significant effect on the amount of total soluble sugars during seed germination. so that under stress conditions, the total amount of soluble sugars increased due to priming. the amount of total soluble sugars in both genotypes under stress conditions was higher than the control, but in the majar, its amount was higher than amol. simultaneously with the increase of soluble sugars during germination, the amount of starch decreased and the activity of alpha-amylase increased. also, the significant increase of soluble sugars under stress conditions was accompanied by a significant decrease in starch and an increase in alpha-amylase enzyme activity. priming significantly decreased starch and increased alpha-amylase of primed seeds of two genotypes under salt stress conditions. therefore, the increase of soluble sugars in primed seeds under salinity stress conditions is another mechanism that improved resistance to salinity stress. seed priming increased proline in majar, while in amol, priming decreased the proline level. until the seed imbibition stage, the amount of proline under stress conditions was significantly lower than the seeds under control conditions, but during the germination stage, the amount of proline increased significantly under salt stress conditions. the results showed that proline did not play a significant role in the osmotic regulation of silybum marianum seedlings. conclusion: in general, priming improved the germination of studied genotypes of silybum marianum seeds under salt stress compared to non-stress conditions. the reactions of both genotypes to priming and salt stress were different. seed priming increased soluble sugars total level and alpha amylase activity and decreased starch level in majar in comparison to in amol.