The present research attempted to investigate the role of sodium nitroprusside (SNP) as a NO donor in yield and accumulation of active substances in milk thistle under drought stress in a 2-year farm experiment. In this experiment, two genotypes of milk thistle (Hungarin and Sari) were sprayed with SNP solutions (0, 100, and 200 µM) under water stress (control or withholding of irrigation from the stages of stem elongation and anthesis). Withholding of irrigation decreased the grain and silymarin yield and increased malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content. Application of 100 µM SNP decreased the content of MDA and H₂O₂ in plants submitted to water deficit and as a result, prevented silymarin yield reduction under stress by increasing grain yield. In both years, with increasing the intensity of stress, taxifolin content, silychristin, silybin A and B, as well as isosilybin B were increased in both genotypes. While, exogenous NO further enhanced taxifolin, silychristin, silybin B, and isosilybin B accumulation, compared with plants solely grown under water deficit without SNP. The results of this study indicated that SNP application, especially at the dose of 100 µM, prevented the leaf water loss and reduces irrigation times from eight times to six or four times under drought stress from the stages of anthesis and stem elongation, respectively, and thus improved grain yield in milk thistle. Moreover, exogenous application of SNP to increasing taxifolin synthesis further enhanced secondary metabolites’ performance under conditions with low water availability.

本研究试图在两年的农场试验中研究硝普钠（SNP）作为NO供体在干旱胁迫下奶蓟中活性物质的产量和累积中的作用。在该实验中，在水分胁迫下（从茎伸长和开花期开始控制或停止灌溉），用SNP溶液（0、100和200 µM）喷洒两种基因型的乳蓟（Hungarin和Sari）。停止灌溉会降低谷物和水飞蓟素的产量，并增加丙二醛（MDA）和过氧化氢（H ₂ O ₂）的含量。100 µM SNP的使用降低了MDA和H ₂ O ₂的含量水分不足的植物中，其结果是通过增加谷物产量来防止水飞蓟素在胁迫下的产量下降。在这两年中，随着压力强度的增加，两种基因型的滑石粉含量，水飞蓟素，水飞蓟宾A和B以及异水飞蓟宾B均增加。同时，与仅在缺水无SNP的条件下生长的植物相比，外源NO进一步增强了滑石粉，水飞蓟素，水飞蓟宾B和异水飞蓟宾B的积累。这项研究的结果表明，在干旱胁迫下，从花期和茎伸长的阶段开始，特别是在100 µM的剂量下，施用SNP可以防止叶片水分流失，并将灌溉时间从八倍减少到六倍或四倍。因此提高了水飞蓟的谷物产量。而且，