Copper (Cu) pollution of agricultural land is a major threat to crop production.Exogenous chemical treatment is an easily accessible and rapid approach to remediate metal toxicity, including Cu toxicity in plants.• We compared the effects of ascobin (ASC; ascorbic acid:citric acid at 2:1) and glutathione (GSH) in mitigation of Cu toxicity in rice.• Plants subjected to Cu stress displayed growth inhibition and biomass reduction, which were connected to reduced levels of chlorophylls, RWC, total phenolic compounds, carotenoids and Mg 2+ . Increased accumulation of ROS and malondialdehyde indicated oxidative stress in Cu-stressed plants. However, application of ASC or GSH minimized the inhibitory effects of Cu stress on rice plants by restricting Cu 2+ uptake and improving mineral balance, chlorophyll content and RWC. Both ASC and GSH pretreatments reduced levels of ROS and malondialdehyde and improved activities of antioxidant enzymes, suggesting their roles in alleviating oxidative damage. A comparison on the effects of ASC and GSH under Cu stress revealed that ASC was more effective in restricting Cu 2+ accumulation (69.5% by ASC and 57.1% by GSH), Ca 2+ and Mg 2+ homeostasis, protection of photosynthetic pigments and activation of antioxidant defence mechanisms [catalase (110.4%), ascorbate peroxidase (76.5%) and guaiacol peroxidase (39.0%) by ASC, and catalase (58.9%) and ascorbate peroxidase (59.9%) by GSH] in rice than GSH, eventually resulting in better protection of ASCpretreated plants against Cu stress. • In conclusion, although ASC and GSH differed in induction of stress protective mechanisms, both were effective in improving rice performance in response to Cu phytotoxicity.

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Cold stress has become problematic for rice seedling production in many sub-tropical areas, including in Bangladesh. Cold stress causes poor germination, stunted seedlings, chlorosis or withering, and limited tillering. Application of various exogenous stimulants metabolically prepares plants to fight against cold stress. This review summarized the role of different exogenous stimulants in mediating cold tolerance in rice seedlings. Seed priming or seedling treatment with exogenous stimulants can be promising approach to improve cold stress tolerance. However, additional research should be conducted to reveal the molecular mechanisms, as well as field level trials should be conducted to determine field level applicability.