Jasmonic acid (JA) is an important phytohormone, which among others may be involved in the regulation of plant accumulating heavy metal. This experiment was designed to explore the effects of exogenous JA on the responses of alfalfa to Cu stress (100 μM) in Hoagland solution. When 1, 5 or 10 mM JA was added to the treatment with Cu addition, Cu concentrations in roots and leaves of alfalfa were significantly decreased (p < 0.05) to some extents compared to the treatment without JA addition. The biomasses of roots and leaves of alfalfa in treatments of JA additions were significantly increased (p < 0.05) compared to the Cu stress treatment. Similarly, the concentrations of Chlorophyll, antioxidant enzyme activities, MDA and H2O2 were improved accordingly. But these factors of JA were not improved further when its concentration added in media was the highest (10 mM), indicating its improvement roles were limited. These results suggested that there were positive roles of exogenous JA on alfalfa decreased its Cu accumulation and toxicities might via reduced oxidative stress.

中文翻译：

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外源茉莉酸减少了紫花苜蓿的铜积累，改善了其光合色素和抗氧化系统。

茉莉酸（JA）是一种重要的植物激素，可能与植物体内重金属的积累有关。设计该实验旨在探讨外源JA对Hoagland溶液中苜蓿对Cu胁迫（100μM）响应的影响。与不添加JA的处理相比，向添加Cu的处理中添加1、5或10 mM JA时，紫花苜蓿的根和叶中的Cu浓度显着降低（p <0.05）。与铜胁迫处理相比，添加JA的处理中苜蓿根和叶的生物量显着增加（p <0.05）。同样，叶绿素浓度，抗氧化酶活性，MDA和H2O2也相应提高。但是，当添加到培养基中的浓度最高（10 mM）时，JA的这些因素并没有得到进一步改善，这表明其改善作用是有限的。这些结果表明，外源JA对紫花苜蓿具有积极作用，可降低其铜积累，并可能通过降低氧化应激而降低毒性。