This study examined the effects of exogenous citrulline (control, 1 and 2 mM) and water availability (100%, 50% and 25% WA) on antioxidant attributes and essential oil constituents of Hyssopus officinalis L. in two successive harvests. Hyssop tolerantly responded to water deficiency by well-promoted antioxidant enzymes (i.e., superoxide dismutase, and catalase), strong DPPH-scavenging activity, and increasing polyphenols; however, the essential oil content was negatively reduced by water stress. External citrulline further increased the activity of antioxidant enzymes. Citrulline application at 2 mM under severe water stress could also improve essential oil (EO) content in the first and second harvests by about 15 and 30%, respectively. Furthermore, under severe drought, citrulline at 2 mM could obtain the highest yield of isopinocamphone (47%) as the main component of EO. The results showed the high potential of this novel applied metabolite agent to be used in a well-fulfilled production of this medicinal plant.

本研究抗氧化属性和精油成分外源瓜氨酸（对照，1和2毫摩尔）和水的可用性（100％，50％和25％WA）的影响神香草L.连续两次收获。牛膝草对水分缺乏的反应是通过充分促进抗氧化酶（即超氧化物歧化酶和过氧化氢酶），强DPPH清除活性和增加多酚来应对的。然而，水分胁迫使精油含量降低了。外部瓜氨酸进一步增加了抗氧化酶的活性。在严重的水分胁迫下，以2 mM的量施用瓜氨酸还可以分别使第一季和第二季收获的精油（EO）含量分别提高约15％和30％。此外，在严重干旱下，瓜氨酸为2 mM可能获得最高产量的异烟酰胺（47％）作为EO的主要成分。结果表明，这种新型应用的代谢产物剂在该药用植物的充分生产中具有很高的潜力。