Department of Horticulture Science, College of Agriculture and Natural Resources, University of Tehran, P.O.Box 31587 77871, Karaj, Iran.
Department of Horticultural Science, Faculty of Agriculture, University of Maragheh, P.O.Box 55136-553, Maragheh, Iran.
BMC Plant Biol. 2023 Jun 10;23(1):309. doi: 10.1186/s12870-023-04312-w.
Salinity, a severe worldwide issue, compromises the economic production of medicinal plants including mints and causes drug-yield decline. γ-Aminobutyric acid (GABA) is a tolerance-inducing signaling bio-molecule in various plant physiological processes. Pineapple mint (Mentha suaveolens Ehrh.) is a valuable medicinal herb with an exhilarating scent of citrus fruit. Piperitenone oxide is the major bioactive constituent of its essential oil, having significant demand by pharmaceutical industries. Nonetheless, modeling and optimizing the effective concentration of GABA remain within twin foci of interest. Therefore, a two factor-five level (NaCl 0-150 mM and GABA 0-2.4 mM) central composite design was conducted to model and optimize drug yield and physiological responses of M. suaveolens. Based on the design of experiments (DoE) approach, different linear, quadratic, cubic, and quartic models were assigned to the response variables. Change trends of shoot and root dry weights followed a simple linear model, whereas sophisticated models (i.e., multiple polynomial regression) were fitted to the other traits. NaCl stress inevitably reduced root and shoot dry weight, piperitenone oxide content, relative water content, pigments content, and maximum quantum yield of PSII. However, content of malondialdehyde (MDA) and total flavonoid, and DPPH radical scavenging activity were increased under salinity. Under severe NaCl stress (150 mM), the essential oil content (0.53%) was increased three times in comparison with control (0.18%). Optimization analysis demonstrated that the highest amount of essential oil (0.6%) and piperitenone oxide (81%) as a drug yield-determining component would be achievable by application of 0.1-0.2 mM GABA under 100 mM NaCl. The highest dry weight of root and shoot was predicted to be achieved at 2.4 mM GABA. Overall, extremely severe NaCl stress (i.e., more than 100 mM) in which a sharp drop in yield components value was observed seemed to be out of M. suaveolens salinity tolerance range. Hence, it is rationale to compensate the decrease of drug yield by foliar application of a dilute GABA solution (i.e., 0.1-0.2 mM) under 100 mM NaCl stress or lower levels.
盐度是一个全球性的严重问题，它会降低包括薄荷在内的药用植物的经济产量，并导致药物产量下降。γ-氨基丁酸（GABA）是各种植物生理过程中诱导耐受的信号生物分子。菠萝薄荷（Mentha suaveolens Ehrh.）是一种有价值的药用草本植物，具有柑橘类水果的清新香气。胡椒烯酮氧化物是其精油的主要生物活性成分，受到制药行业的高度需求。然而，建模和优化 GABA 的有效浓度仍然是两个关注焦点。因此，进行了一个两因素五水平（NaCl 0-150 mM 和 GABA 0-2.4 mM）中心组合设计，以对 M. suaveolens 的药物产量和生理反应进行建模和优化。根据实验设计（DoE）方法，不同的线性、二次、三次和四次模型被分配给响应变量。茎和根干重的变化趋势遵循简单的线性模型，而其他性状则采用复杂的模型（即多元多项式回归）进行拟合。NaCl 胁迫不可避免地降低了根和茎的干重、胡椒烯酮氧化物含量、相对含水量、色素含量和 PSII 的最大量子产量。然而，在盐胁迫下，丙二醛（MDA）和总类黄酮的含量以及 DPPH 自由基清除活性增加。在严重的 NaCl 胁迫（150 mM）下，与对照（0.18%）相比，精油含量（0.53%）增加了三倍。优化分析表明，在 100 mM NaCl 下应用 0.1-0.2 mM GABA 可获得最高的精油（0.6%）和作为药物产量决定成分的胡椒烯酮氧化物（81%）。预测在 2.4 mM GABA 下可获得根和茎的最大干重。总的来说，在观察到产量成分值急剧下降的极其严重的 NaCl 胁迫（即超过 100 mM）下，似乎超出了 M. suaveolens 的耐盐范围。因此，在 100 mM NaCl 胁迫或更低水平下，通过叶面喷施稀释的 GABA 溶液（即 0.1-0.2 mM）来补偿药物产量的下降是合理的。
