Abiotic factors in nutrient solutions (NSs), such as salinity and high electrical conductivity (EC), may adversely alter plant growth and crop performance. However, there are medicinal/aromatic plants which can not only withstand these adverse conditions, but which can also increase their productivity or even enhance their quality in such conditions. As fresh water sources suitable for irrigation are becoming more and more limited, the use of low-quality water sources and hydroponic growing systems have been suggested as the main alternatives. Towards that direction, this study aims to evaluate the effect of high EC levels in NSs on geranium (Pelargonium graveolens L’Hér.) and common verbena (Verbena officinallis L.) plants cultivated in a soilless (perlite) hydroponics system. Plants were irrigated with a full nutrient solution of EC 2.1 dS m⁻¹ and pH 5.8 until they reached a uniform size. Then, three treatments were applied, namely: (a) a control treatment with an EC of 2.1 dS m⁻¹ in the NS, (b) a high-salinity NS created by adding 75 mM of NaCl (EC under 8.5 dS m⁻¹) and (c) a concentrated NS with an EC of 8.5 dS m⁻¹. In pelargonium, high salinity decreased the total phenolic and total flavonoid contents; antioxidant capacity; N, K, Mg and P content; as well as chlorophyll fluorescence, compared to the control treatment. On the other hand, increased salinity levels increased the Na and Ca content and stomatal resistance. In common verbena, salinity decreased total phenolic content and chlorophyll fluorescence but increased total flavonoid content; antioxidants; leaf K, P, Na, Cu and Zn content; and stomatal resistance, compared to the control. In both species, high EC did not affect polyphenols, flavonoids or antioxidants, whereas it increased stomatal resistance and nutrient accumulation in the leaves, and decreased chlorophyll fluorescence compared to the control treatment. Damage indices, indicated by lipid peroxidation, hydrogen peroxide production and the elevation of enzymes’ antioxidant activities, were evidenced in both saline- and high-EC-treated plants. In conclusion, despite having the same EC levels in the nutrient solution, it seems that ionic stress caused by high mineral concentrations in the nutrient solution had less severe effects on the tested plants than the relevant osmotic stress caused by high salinity due to the addition of NaCl in the nutrient solution.

中文翻译：

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水培天竺葵和马鞭草在盐度和高电导率水平下的性能

营养液 (NS) 中的非生物因素，例如盐度和高电导率 (EC)，可能会对植物生长和作物性能产生不利影响。但是，有些药用/芳香植物不仅可以承受这些不利条件，而且还可以在这些条件下提高其生产力甚至提高其质量。随着适合灌溉的淡水资源越来越有限，已建议使用低质量水源和水培种植系统作为主要替代方案。朝着这个方向，本研究旨在评估 NSs 中高 EC 水平对天竺葵 ( Pelargonium Graveolens L'Hér.) 和马鞭草 ( Verbena officinallis) 的影响L.) 在无土（珍珠岩）水培系统中栽培的植物。用EC 2.1 dS m ^-1和pH 5.8的全营养液灌溉植物，直到它们达到均匀的大小。然后，应用三种处理，即：（a）在 NS 中EC 为 2.1 dS m ^-1的对照处理，（b）通过添加 75 mM NaCl（EC 低于 8.5 dS m ^-）产生的高盐度 NS ¹ ) 和 (c) 浓缩 NS，EC 为 8.5 dS m ^-1. 在天竺葵中，高盐度降低了总酚和总黄酮含量；抗氧化能力；N、K、Mg、P含量；以及与对照处理相比的叶绿素荧光。另一方面，盐度增加会增加 Na 和 Ca 含量以及气孔阻力。在马鞭草中，盐度降低了总酚含量和叶绿素荧光，但增加了总黄酮含量；抗氧化剂；叶K、P、Na、Cu和Zn含量；和气孔抗性，与对照相比。在这两个物种中，高 EC 不影响多酚、类黄酮或抗氧化剂，但与对照处理相比，它增加了气孔抗性和叶片中的养分积累，并降低了叶绿素荧光。损伤指数，由脂质过氧化指示，在盐水和高 EC 处理的植物中都证明了过氧化氢的产生和酶的抗氧化活性的提高。总之，尽管营养液中的 EC 水平相同，但似乎营养液中高矿物质浓度引起的离子胁迫对受试植物的影响不如由添加的高盐度引起的相关渗透胁迫严重。营养液中的氯化钠。