Glycyrrhiza glabra L. (licorice) is a medicinal species rich in the specialised plant metabolite glycyrrhizin. It has been previously proposed that drought, which is increasing in importance due to the climatic change and scarcity of water resources, can promote the synthesis of glycyrrhizin. The effects of slight, moderate and intense drought (70, 35 and 23% of the regular irrigation, respectively) on growth parameters, osmolyte content, oxidative stress markers, antioxidant enzymes, glycyrrhizin biosynthesis genes and root glycyrrhizin concentration and contents, have been assessed in five Iranian licorice genotypes grown in the field. Drought decreased progressively biomass and leaf relative water contents, and increased progressively osmolyte (proline, glycine-betaine and soluble sugars) concentrations in leaves and roots. Drought caused oxidative stress in leaves, as indicated by lipid peroxidation and hydrogen peroxide concentrations, and increased the activities of antioxidant enzymes in leaf extracts (catalase, peroxidase, superoxide dismutase and pholyphenoloxidase). Drought promoted the synthesis of glycyrrhizin, as indicated by the increases in the expression of the glycyrrhizin biosynthesis pathway genes SQS1, SQS2, bAS, CYP88D6, CYP72A154 and UGT73, and increased the root concentrations of glycyrrhizin with drought in some genotypes. However, the large decreases in root biomass caused by drought led to general decreases in the amount of glycyrrhizin per plant with moderate and intense drought, whereas the slight drought treatment led to significant decreases in glycyrrhizin content in only one genotype. Under intense drought two of the genotypes were still capable to maintain half of the control glycyrrhizin yield, whereas in the other three genotypes glycyrrhizin yield was 22-33% of the control values. Results indicate that under intense drought, with only 23% of the normal water dose being applied, an appropriate choice of genotype can still lead to acceptable glycyrrhizin yields.

中文翻译：

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干旱胁迫对田间生长的甘草（Glycyrrhiza glabra L.）生长参数、渗透物含量、抗氧化酶和甘草甜素合成的影响

Glycyrrhiza glabra L.（甘草）是一种富含特殊植物代谢产物甘草甜素的药用物种。先前有人提出，由于气候变化和水资源稀缺，干旱的重要性日益增加，可以促进甘草甜素的合成。已评估轻度、中度和重度干旱（分别为常规灌溉的 70%、35% 和 23%）对生长参数、渗透物含量、氧化应激标记物、抗氧化酶、甘草甜素生物合成基因和根部甘草甜素浓度和含量的影响在田间种植的五种伊朗甘草基因型中。干旱逐渐降低生物量和叶片相对水分含量，并逐渐增加叶片和根中渗透物（脯氨酸、甘氨酸-甜菜碱和可溶性糖）的浓度。干旱引起叶片氧化应激，如脂质过氧化和过氧化氢浓度所示，并增加叶片提取物中抗氧化酶（过氧化氢酶、过氧化物酶、超氧化物歧化酶和多酚氧化酶）的活性。干旱促进了甘草甜素的合成，如甘草甜素生物合成途径基因 SQS1、SQS2、bAS、CYP88D6、CYP72A154 和 UGT73 的表达增加，并且在某些基因型中随着干旱增加了甘草甜素的根浓度。然而，干旱引起的根生物量大幅下降导致每株甘草甜素含量在中度和重度干旱下普遍下降，而轻度干旱处理仅导致一种基因型甘草甜素含量显着下降。在严重干旱下，其中两种基因型仍能维持对照值的一半甘草甜素产量，而在其他三种基因型中，甘草甜素产量为对照值的 22-33%。Results indicate that under intense drought, with only 23% of the normal water dose being applied, an appropriate choice of genotype can still lead to acceptable glycyrrhizin yields.