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Okra pod is sensitive to low temperature, which results in chilling injury under improper low‐temperature storage. This study aimed to evaluate the effect of different concentrations of methyl jasmonate (MeJA) treatment on okra pod stored at 4 ± 1°C for 12 days and illuminate the mechanism of MeJA alleviating chilling injury. Compared to the control, MeJA treatments maintained lower relative electric conductivity (REC), chilling injury (CI) degree, and lignin content, as well as higher total soluble solids, total soluble sugar, pectin content, and chlorophyll content. The factor analysis was applied to comprehensively evaluate the effects of MeJA so that 1 μmol/L MeJA was screened as the optimum concentration to maintain the okra quality throughout the storage time. In contrast with control, MeJA not only accelerated the generation of antioxidant substances (phenolics and flavonoids) but also increased the superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) activity, inhibited malondialdehyde (MDA), hydrogen peroxide (H2O2) content accumulation, and the polyphenol oxidase (PPO) activity. This work confirmed that MeJA could effectively alleviate chilling injury and maintain the quality during cold‐stored by regulating reactive oxygen species (ROS) metabolism. These results provide theoretical guidance for the application of MeJA in okra storage and preservation.

The aim of this study was to investigate the effect of 20 mg/L 2,4-D on the quality during ripening of on-tree longan fruits. We investigated external and internal properties of the on-tree longan fruits. The results showed that 2,4-D treatment promotes the growth based on the fruit size and weight. The respiration rate, contents of TSS, total soluble sugar, sucrose, glucose, fructose, and hexose revealed an increasing tendency with advancing the maturity and reached the high status during 110-126DPA. By contrast, the relative electric conductivity and TA content displayed a declining trend during the ripening stage, increase with the senescence. All these pieces of information indicated that 2,4-D treatment could effectively promote the sensory quality of on-tree longan fruit, prolong the harvest time to 118DPA, while CK should harvest before 110DPA.

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Amaranthus tricolor L. is a cultivated green vegetable, commonly known as amaranth, which is similar to spinach, broccoli, and cabbage. In the present study, we investigated the antioxidant and antimicrobial activities of the methanol extract and various fractions from A. tricolor. Results show that A. tricolor ethyl acetate (EtOAc) extract displayed the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging activity (IC50=16.43±1.53 μg/ml), which was higher than that of the positive control, butyl hydroxy anisd (IC50=19.42±0.91 μg/ml). This extract had a reducing power of 2.743 at 0.5 mg/ml and significantly attenuated production of reactive oxygen species in a dose-dependent manner. Further bioassay-monitored fractionation of the EtOAc extract yielded two flavonoids, kaempferol (1) and quercetin (2), and one phenolic acid, gallic acid (3). We found that the antimicrobial activity of compound 3 (at a dose of 63 μg/mL) was superior to that of the tetracycline control (at a dose of 250 μg/mL) against Escherichia coli. Additionally, compounds 1 and 2 (at a dose of 63 μg/mL each) displayed higher activities against Penicillium oxalicum and Staphylococcus aureus than the control. These results suggest that A. tricolor extract may represent a promising nutraceutical source due to the antioxidant and antimicrobial properties of its phenolic compounds.