(1) Background: The growth of plants is impacted by salinity and alkali, Lilium pumilum (L. pumilum) is an ornamental plant with strong resistance to salinity and alkali, while the LpPsbP gene is helpful to fully understand the Saline-Alkali tolerance of L. pumilum. (2) Methods: Gene cloning, bioinformatics analysis, expression of fusion protein, determination of physiological indices of plant after Saline-Alkali stress, yeast two-hybrid screening, luciferase complementation assay, chromosome walking to obtain the promoter sequence, and then analyzed by PlantCARE. (3) Results: The LpPsbP gene was cloned and the fusion protein was purified. The transgenic plants had higher Saline-Alkali resistance than the wild type. A total of eighteen proteins interacting with LpPsbP were screened, and nine sites in the promoter sequence were analyzed. (4) Conclusion: Under Saline-Alkali or oxidative stress, L. pumilum will promote the expression of LpPsbP, which will then directly scavenge reactive oxygen species (ROS) in order to protect its photosystem II, reduce its damage, and thus improve the Saline-Alkali resistance of the plant. Moreover, according to some of the literature and the following experiments, two additional speculations are developed on the mechanisms of how two newly found objects, namely jasmonic acid (JA) and FoxO protein, could be involved in ROS scavenging processes were made.

· Ferric reduction oxidase plays important roles in the attraction of iron to plants, which is also involved in how plants react to biotic and abiotic stressors. However, the molecular mechanism of ferric reduction oxidase ( LpFRO7) from Lilium pumilum responding to NaHCO is unknown. ·RT-qPCR and bacterial solution resistance analysis were used to demonstrate that LpFRO7 is tolerant to NaHCO . Overexpressing LpFRO7 L. pumilum enhances plant tolerance to NaHCO . The wilting degree and H O content of LpFRO7 overexpressed lines was relatively lower than that of wild type under NaHCO treatment. In addition, the stomatal changes of the overexpressed lines were smaller, and the ferrite reductase activity, chlorophyll content, iron content, and respiration rate were greater than those of the wild type. ·The bHLH family is participating in the ROS signaling pathway. We demonstrate that the LpbHLH115 transcription factor binds to the promoter of LpFRO7 using EMSA, Yeast one-hybrid assay, and luciferase complementation assay. ·By using yeast two-hybrid, 8 distinct interacting proteins were discovered. Yeast two-hybrid assay and BiFC assay were perform to verify whether there is a reciprocal relationship between LpFRO7 and LpTrx. ·Our results showed that LpFRO7 increases the tolerance of L. pumilum to NaHCO through the ROS signaling pathway.