Mobilizing the seed storage oil in milk thistle (Silybum marianum) can supply energy for seed germination and early seedling growth and apply as TAGs breakdown marker

Abstract

Milk thistle (Silybum marianum) is a crucial medicinal plant containing a large amount of oil. In the study, the changes in storage oil during seed germination and seedling transition from heterotrophic phases were investigated. The results showed that seed oil decreased from 19.53% to 0.88% on the 7th day of seedling development. Oil hydrolysis continued until the 4th day of germination with a low slope, but then increased the use of oils in seed germination end seedling growth metabolism. The results indicated that the quantitative changes in fatty acids, presented at lower amount, were relatively higher than dominant fatty acids. There were decreasing phenolic content in the developing seedlings, but overall, lowest level of total phenolic content can be attributed to the control (30.52 ​mg· 100 ​g· Oil−1). In contrast, the maximum peroxide value (2.58 meq· kg Oil−1) in the developing seedling was observed on the last day of the experiment. The results showed that there was a significant correlation between saturated fatty acid, unsaturated fatty acid, and lipase activity. However, the correlation between lipase activity and polyunsaturated fatty acids was significantly higher than between lipase activity and monounsaturated fatty acids (R2 ​= ​90% and R2 ​= ​77%, respectively). Therefore, the lipolysis process acts selectively in milk thistle oils. According to the results, C12:0 exhibits a greater impact on the early seedling growth rather than on the germination process and is one of the determining factors in the transition from heterotroph to autotroph. Also, it can be a marker for TAGs breakdown.