## 5 Conclusions  
Our study is summarised in a schematic pathway (Figure 8) which illustrates that magnetopriming of soybean seeds enhanced the NO production by up-regulation of genes of enzymes related to NOS-like and NR along with their enhanced activities. The comparison of the two biosynthetic pathways showed that the contribution of NR towards NO production is more than that of NOS-like, which is supported by the results obtained from the treatment of different inhibitors (ST and L-NAME) of the two enzymes under non-saline and saline conditions. The _GmNOS-like 2_ and _GmNR1_ genes could be ideal candidates to be characterised towards their involvement in the NO production in soybean. There is an inverse correlation between STI and Na\({}^{+}\)/K\({}^{+}\) ratio, i.e., the STI values are higher and Na\({}^{+}\)/K\({}^{+}\) ratio lower in the seedlings that emerged from MP and SNP + MP treatments in non-saline as well as in saline conditions. The higher GA and IAA content with lower ABA/GA and IAA/GA ratios in the magnetoprimed seeds under both the non-saline and saline conditions indicated that priming induced NO production had lowered the Na\({}^{+}\)/K\({}^{+}\) ratio to increase the salt tolerance index in soybean seeds. Thus, MP-induced NO production is directed towards the homeostasis of these hormones to favour the germination and seedling growth in the presence or absence of salt.  
**Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/cells11142174/s1](https://www.mdpi.com/article/10.3390/cells11142174/s1)]([https://www.mdpi.com/article/10.3390/cells11142174/s1](https://www.mdpi.com/article/10.3390/cells11142174/s1)), Table S1: List of putative NOS-like and NR genes in soybean. References [45,87] are cited in Supplementary Materials.  
**Author Contributions:** Conceptualization, S.K. ([PERSON]); methodology, S.K. ([PERSON]), A.A., R.K.R. and S.K. ([PERSON]); software, S.K. ([PERSON]), A.W. and A.A.; validation, S.K. ([PERSON]), A.A. and R.K.R.; formal analysis, S.K. ([PERSON]), A.A, R.K.R. and S.K. ([PERSON]); investigation, S.K. ([PERSON]); resources, S.K. ([PERSON]), A.A., M.J., A.W. and M.B.; data curation, S.K. ([PERSON]); writing--original draft preparation, S.K. ([PERSON]), A.A. and R.K.R.; writing--review and editing, S.K. ([PERSON]), A.A., R.K.R., M.J. and M.B.; visualization, S.K. ([PERSON]) and A.A.; supervision, S.K. ([PERSON]); project administration, S.K. ([PERSON]); funding acquisition, S.K. ([PERSON]) and M.B. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The work was supported by the grant received by the first author under the Women Scientists Scheme-A (DST/SR/WOS-A/LS-17/2017) of Department of Science and Technology, New Delhi, India.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data can be obtained on request from the authors.  
Figure 8: Proposed model for magnetopriming-induced salt tolerance in soybean seeds. Magnetopriming of soybean seeds promotes NO synthesis via (I) Nitrate reductase and (II) Nitric oxide synthase-like. There may be involvement of (III) Plasma membrane H\({}^{+}\)-ATPase and (IV) Na\({}^{+}\)/H\({}^{+}\) antiporter. The Na\({}^{+}\) influx may be regulated by enzyme activities of plasma membrane III and IV. NO regulates homeostatic control of ABA/GA and IAA/GA ratio in magnetoprimed seeds. Overall, magnetopriming-induced NO-mediated homeostasis of germination hormones and lower Na\({}^{+}\)/K\({}^{+}\) ratio improve the salt tolerance index in soybean seeds. SOD = Superoxide dismutase, CAT = Catalase.  
**Acknowledgments:** The authors thanks to [PERSON] for assistance in HPLC.  
**Conflicts of Interest:** The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.