Rosa roxburghii fruit has a short postharvest shelf life, with rapid declines in quality and antioxidant capacity. This research assessed how phytic acid affects the antioxidant capacity and quality of R. roxburghii fruit while in the postharvest storage period and reveals its potential mechanism of action. The findings suggested that phytic acid treatment inhibits the production of malondialdehyde (MDA) and enhances the activities and expressions of glutathione peroxidase (GPX), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) while decreasing the generation of superoxide anions (O₂^•−) and hydrogen peroxide (H₂O₂). Phytic acid treatment activates the ascorbate–glutathione (AsA-GSH) cycle and enhances the activity and expression of key enzymes in the cycle: ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR). It also increases the levels of non-enzymatic antioxidants, such as ascorbic acid (AsA) and glutathione (GSH), while reducing the production of dehydroascorbic acid (DHA) and oxidized glutathione (GSSG). Moreover, phytic acid treatment enhances the ratios of AsA/DHA and GSH/GSSG, maintaining the reduced state of the fruit. In summary, phytic acid improves antioxidant defense system and activates the AsA-GSH cycle, alleviating oxidative damage and ensuring R. roxburghii fruit quality after harvest.

Melatonin treatment has been reported to effectively preserve and improve the postharvest quality of fruits and vegetables during storage. This research focused on examining the significance of melatonin on maintaining the quality of fresh Gastrodia elata tubers throughout the storage period. The findings demonstrated that melatonin application effectively reduced the deterioration rate and inhibited the rise in respiratory rate, malondialdehyde content, and weight loss, while slowing down the decline in soluble solid content. Melatonin treatment led to a decrease in hydrogen peroxide production and a rise in non-enzymatic antioxidant concentrations, including ascorbic acid. Furthermore, it boosted both the activity and expression of indispensable antioxidant enzymes, like superoxide dismutase, catalase, and ascorbate peroxidase. Additionally, melatonin treatment promoted the accumulation of total phenols, flavonoids, and lignin in fresh G. elata, while enhancing both the activity and expression of critical enzymes in the phenylpropanoid pathway, including phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumarate-CoA ligase. Moreover, melatonin treatment boosted the activity and expression of energy-associated enzymes including H⁺-ATPase, succinate dehydrogenase, Ca²⁺-ATPase, and cytochrome C oxidase, contributing to the improvement of energy levels in fresh G. elata. In summary, melatonin enhances the antioxidant potential and reduces oxidative damage in fresh G. elata by activating reactive oxygen species, phenylpropanoid metabolism, and energy metabolism, thereby maintaining its postharvest quality.

Fresh Gastrodia elata tubers are highly perishable after harvest because pathogen infection accelerates quality deterioration and limits their storage and commercial utilisation. This study examined lesion development in wounded, pathogen-inoculated tubers held at 24 ± 1 °C and, in a separate experiment, quality and physiological changes in non-inoculated tubers stored at 4 ± 1 °C. In the inoculation assay, 1 mM salicylic acid (SA) reduced lesion development following inoculation with Fusarium sp. (isolate 1022-1-1) and Aspergillus sp. (isolate 1022-11). During cold storage, SA-treated tubers maintained higher soluble solid content and showed less weight loss, membrane permeability, and malondialdehyde accumulation than controls. SA application promoted the enzymatic activities and transcriptional expression of superoxide dismutase, catalase, and peroxidase. It also activated the ascorbate–glutathione cycle by promoting ascorbic acid and glutathione accumulation, along with increasing the enzymatic activities and transcript abundance of several cycle-related enzymes, including ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, and dehydroascorbate reductase. These responses limited superoxide anion production and excessive hydrogen peroxide accumulation, thereby alleviating oxidative damage. SA enhanced phenylpropanoid metabolism through the upregulation of phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, and 4-coumaroyl-CoA ligase at both enzymatic and transcriptional levels, contributing to increased levels of total phenolics, flavonoids, and lignin. Furthermore, SA contributed to ATP maintenance by upregulating hexokinase, succinate dehydrogenase, cytochrome c oxidase, H⁺-ATPase, and Ca²⁺-ATPase at both enzymatic and transcriptional levels. Overall, SA treatment reduced lesion development in inoculated G. elata tubers and helped maintain the quality of non-inoculated tubers during cold storage.