Vertical hydroponics farming has emerged as an alternative solution to feed the continuously growing world population. Additionally, recent studies reported that the exogenous treatments of jasmonic acid influence the phytochemical composition of Brassicaceae. We conducted this study to determine the effect of preharvest methyl jasmonate (MeJA) treatment on the phytochemical composition and antioxidant activities of soil- and hydroponically grown pak choi. An aqueous solution of 0.5-mM MeJA was sprayed to saturation on the aerial plant part three days before harvest. The harvested pak choi was freeze-dried and then powdered to measure the antioxidant activity and the contents of chlorophylls (Chls), total phenolics and flavonoids, and glucosinolates (GSLs). The overall results revealed that pak choi grown in vertical hydroponics had higher total Chls and total phenolics than those grown in soil in the greenhouse, regardless of MeJA treatment. Nevertheless, the GSLs content and total flavonoids increased significantly due to MeJA treatment in both growing systems, and the highest values were recorded in hydroponically grown MeJA-treated pak choi. Similarly, the 2, 2-di-phenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, Trolox-equivalent antioxidant capacity (ABTS), oxygen radical absorbance capacity (ORAC), and ferric-reducing antioxidant power (FRAP) were highest in hydroponically grown MeJA-treated pak choi. Taken together, the preharvest foliar treatment of MeJA can be used to improve the phytochemical composition of pak choi grown in both growing systems. Interestingly, the results strongly support the use of MeJA treatment in the vertical hydroponics growing system compared to the conventional growing system in the soil. This indicates that supplementing the vertical hydroponic growing system with preharvest MeJA treatment could be the best option to improve both the yield per square meter and the quality of pak choi. Besides, MeJA-treated pak choi could be used as a value-added horticultural commodity, as its antioxidant activity increased after treatment. Moreover, after further studies, MeJA could also be applied to other Brassica vegetables to improve their GSL contents and antioxidant properties.

中文翻译：

---

采前茉莉酸甲酯处理提高了水培小白菜的抗氧化活性和芥子油苷含量


垂直水培农业已成为养活不断增长的世界人口的替代解决方案。此外，最近的研究报告称，茉莉酸的外源处理会影响十字花科植物的植物化学成分。我们进行这项研究是为了确定采前茉莉酸甲酯 (MeJA) 处理对土壤和水培小白菜的植物化学成分和抗氧化活性的影响。收获前三天，将 0.5-mM MeJA 水溶液喷洒到气生植物部分上至饱和。将收获的小白菜冷冻干燥，然后磨成粉末，测定其抗氧化活性以及叶绿素（Chls）、总酚和黄酮类化合物以及芥子油苷（GSL）的含量。总体结果表明，无论是否进行 MeJA 处理，在垂直水培法中生长的小白菜比在温室土壤中生长的小白菜具有更高的总叶绿素和总酚类物质。然而，由于 MeJA 处理，两个生长系统中的 GSL 含量和总黄酮类化合物显着增加，并且水培生长的 MeJA 处理的小白菜中记录了最高值。同样，2, 2-二苯基-1-三硝基苯肼（DPPH）自由基清除能力、Trolox 等效抗氧化能力（ABTS）、氧自由基吸收能力（ORAC）和铁还原抗氧化能力（FRAP）在水培种植的经 MeJA 处理的小白菜。总而言之，MeJA 的采前叶面处理可用于改善两种生长系统中生长的小白菜的植物化学成分。有趣的是，与传统的土壤种植系统相比，结果强烈支持在垂直水培种植系统中使用 MeJA 处理。 这表明，在垂直水培种植系统中添加采前 MeJA 处理可能是提高小白菜每平方米产量和品质的最佳选择。此外，经过MeJA处理的小白菜可以用作增值园艺商品，因为处理后其抗氧化活性增加。此外，经过进一步研究，MeJA还可以应用于其他芸苔属蔬菜，以提高其GSL含量和抗氧化性能。