Impact of exogenous salicylic acid and hydrogen peroxide on vitamins, essential nutrients and silymarin content of milk thistle grown at two different altitudes of balochistan under cadmium stress

Abstract

Cadmium (Cd+2), a potentially toxic element, inhibits growth and development of several plant species, especially medicinal plants. However, exogenous supplementation of various hormones, compounds and signaling molecules helps to mitigate the impact of Cd+2 toxicity. Medicinal value of plants in today's era cannot be undermined. Silybum marianum (L.) Gaertn. (milk thistle) is one of most important and valuable medicinal plant; its silymarin content is widely being used to treat liver diseases. The present study was conducted during October 2019–March 2020 to analyze the potential impact of exogenous supplementation with 0.25 μM salicylic acid (SA) and 10 μM hydrogen peroxide (H2O2) priming, foliar and their combinational treatments on various attributes of milk thistle at two diverse ecological zones of Balochistan province of Pakistan, i.e., Quetta (Qta) and Turbat (Tbt) under Cd+2 toxicity. So far, no study conducted considering these two ecological zones of Pakistan with respect to cadmium toxicity on milk thistle nutritional and physio-biochemical attributes. The design of the experiment was randomized complete block design (RCBD) under factorial with three replication each treatment. Results portrayed that SA and H2O2, priming, foliar spray and combinational treatments were quite effective in alleviating the negative impacts of Cd+2 toxicity. The essential nutrients, i.e., nitrate (NO3−), calcium (Ca2+), potassium (K+) and vitamins viz., ascorbic acid (AsA), niacin and riboflavin were affected by Cd+2 induced toxicity; however, the substantial impact of SA and H2O2 helped to reduce the Cd+2 toxicity and boosted up plant nutrients vitamin content. In a nutshell, exogenous treatments of SA and H2O2 enhanced the yield potential by increasing the weight of hundred seeds, enhancing the accumulation of silymarin content in milk thistle seeds which is of prime significance for its medicinal importance in treatment of liver diseases. Therefore, the data obtained in this study highly recommends priming (P) and foliar (F) spray along with combinational treatment of SA and H2O2 as the best strategy to ameliorate Cd+2 toxicity in plants, which will ultimately lead to better growth and yield of the plants.

Keywords

• Abiotic stress
• Altitudinal variation
• Plant growth promoters
• Metal toxicity
• Stress physiology