To investigate the photosynthetic change characteristics of mango leaves under enhanced UV-B radiation, adult ‘Tainong No. 1’ mango (Mangifera indica) trees were treated (N=nine individuals) with simulated enhanced UV-B radiation [24 and 96 kJ/(m2·d)] in the field, and the photochemical reactions, activities of key enzymes in carbon assimilation, and the expression of genes were observed. The results showed that compared with the control, there was a decrease in tree yield and nutritional flavor quality of the fruits under the 96 kJ/(m2·d) treatment, while no significant changes were observed under 24 kJ/(m2·d). After 20 or 40 days, leaves’ net photosynthetic rate (Pn), stomatal conductance (Sc), transpiration rate (Tr), intercellular CO2 concentration (Ci), and chlorophyll a/b under exposure to 96 kJ/(m2·d) of UV-B were significantly lower than in the control, whereas chlorophyll a, chlorophyll b, carotenoids, Hill reaction activity, photochemical quenching coefficient (qP), and Rubisco activities were significantly higher. By contrast, the Hill activity and Rubisco activity under 24 kJ/(m2·d) were significantly higher than the control, while Pn, Sc, Tr, Ci, and the content of photosynthetic pigments were similar to the control. The expression of gene coding the Rubisco big subunit (rbcL) was inhibited by the 96 kJ/(m2·d) treatment. We conclude that stomatal limitation was directly induced by 96 kJ/(m2·d), resulting in the inhibition of photosynthesis and the reduction in yield and deterioration of the quality of mango.

In recent years, magnetic fields have emerged as a non-thermophysical treatment with a signifi-cant impact on microbial fermentation processes. Brassica trispora is a microorganism known for its indus-trial-scale production of lycopene and high yield of single cells. This study aimed to in-vestigate the impact of low frequency magnetic fields on lycopene synthesis by Brassica trispora and elucidate the underlying mechanism for enhancing lycopene yield. The results indicated that both the intensity and duration of the magnetic field treatment influenced the cell. Exposing the cell to a 0.5 mT magnetic field for 48 hours on the second day of fermentation resulted in a lyco-pene yield of 1473.16 mg/L, representing a re-markable increase of 216.1% compared to the con-trol group. Transcriptome analysis revealed that al-ternating magnetic field significantly up-regulated genes related to ROS and cell membrane structure, leading to a substantial increase in lycopene production. Scanning electron microscopy revealed that the magnetic field treatment resulted in rough, loose, wrinkled surface morphology of the mycelium, along with a few mi-cropores, thereby altering the cell membrane permeability to some extent. Moreover, there was a significant increase in intracellular ROS content, cell membrane permeability, key enzyme activi-ty involved in lycopene metabolism, and ROS-related enzyme activity. In conclusion, the alter-nating fre-quency magnetic field can activate a self-protective mechanism that enhances lyco-pene synthesis by modulating intracellular ROS content and cell membrane structure. These find-ings not only deepen our understanding of the impact of magnetic fields on microbial growth and metabolism but also provide valuable insights for developing innovative approaches to en-hance carotenoid fermentation.