Active constituents Changes of Silybum marianum in Water Stress

Water deficit is one of the major abiotic stresses, which adversely affects crop growth and development. These changes are mainly related to the alternation of some metabolic functions. This alteration can resist plant under stresses. Certain plants have devised mechanisms to survive under low water conditions. Usually, water deficit has a positive effect in the biosynthesis of secondary metabolites such that these constraint decrease oxidative stress. In this study to evaluate the effect of Water stress on active substance of Silybum marianum two experiments under pot and field conditions were carried out. In the first experiments, a completely randomized design (CRD) was conducted with four levels of water stress inducing soil water potential of -0.33, -4, -8 and -12 bar. In the second experiment, five treatments inducing soil water potential of –0.33, -4, -8, -12 and –15 bar were applied treatments was applied using a randomized complete block design with four replications. The highest content of Silibin a, b and total amount were measured to be -4 and -12 bar in pot and field experiments respectively. The highest content of Silymarin and oil percentage were accumulated under water potential of -4 bars in both experiments. Thus, the result showed that soil water potential of -4 bar was the best treatment to increase of milk thistle secondry metabolites.