**5. Conclusions**

A recent study reported that seeds primed with SPM exhibited a great capability to mitigate Cr-induced adverse effects in rice seedlings of both cultivars. Cr (100 μM) disclosure in nutrients media severely damaged the plant biomass/growth, impaired the photosynthetic pigment, imbalanced the micro- and macro-nutrients, augmented the cellular oxidative damage, altered the endogenous phytohormone level and cellular ultrastructure, and desynchronized the antioxidant defense system in rice seedlings, especially in CY927. Simultaneously, seeds primed with SPM ameliorated biomass/growth production, chlorophyll pigments, total soluble sugar, total soluble protein, maintained nutrient balance, and improved antioxidants' defense system by lowering the Cr uptake, accumulation, translocation, lipid peroxidation, oxidative damage, and electrolyte leakage. Moreover, SPM modulated the endogenous phytohormones content, as well as the transcription level of SA-related genes (*PR1*, *PR2*, and *NPR1*) under Cr stress. Henceforth, it was revealed that SPM can enhance plant tolerance and mitigate the Cr phytotoxicity in different rice varieties. Furthermore, Cr stress damaged the rice cultivar CY927 more than YLY689. YLY689 was found more tolerant to Cr stress and SPM further enhanced tolerance capacity, while CY927 displayed susceptibility to Cr stress whose negative effects were reversed by SPM.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/antiox11091704/s1, Figure S1. Effect of seed primed with SPM on phenotypic changes of two different rice cultivars under Cr toxicity. (a) Cr-induced phenotypical changes on the CY927 cultivar and mitigation effect of SPM under Cr stress. (b) Cr-induced phenotypical changes on the YLY689 cultivar and mitigation effect of SPM under Cr exposure, Table S1. Primers information.

**Author Contributions:** F.B. and Z.U. have equally contributed to this work as first author. Y.G., J.A.B. and P.A. were involved in conceptualization, Y.G., F.B. and Z.U. designed the experiment. F.B., Z.U., M.N. and A.A. performed the experiment and wrote the manuscript. F.B., Z.U., M.N., B.Z. and A.A. helped in writing, while W.Z. and Y.G. revised/edited the manuscript. B.Z. and P.K. performed the statistical analysis. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Science and Technology Department of Zhejiang Province (2022C02034), Zhejiang Provincial Natural Science Foundation (No. LY21C130006), National Natural Science Foundation of China (No. 32072127), Dabeinong Funds for Discipline Development and Talent Training in Zhejiang University, and Collaborative Innovation Center for Modern Crop Production co-sponsored by Province and Ministry (CIC-MCP). National Natural Science Foundation of China (No. 31800386).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data are contained within the article and Supplementary Materials.

**Acknowledgments:** The authors would like to extend their sincere appreciation to the Researchers Supporting Project Number (RSP-2021/350), King Saud University, Riyadh, Saudi Arabia.

**Conflicts of Interest:** The authors declare no conflict of interest.
