**5. Conclusions**

While modifications in pectin do not allow the cell wall to form an impassable barrier, these elements remain critical in the role of the cell wall as a barrier to stress. While our findings on cell wall rheology, shear force, calcium localization and analysis of water loss in pure pectin standards are indicative that "egg-box" structures and RG-II dimers likely formed, this alone was not sufficient in significantly (*p* > 0.05) improving dehydration stress tolerance. Variation was also observed with respect to resistance to the fungal pathogens of interest, suggesting that while boron and PMEI5 likely play a role in resistance to dehydration stress and fungal pathogens, the true picture appears to be far more nuanced. Overall, our findings demonstrate the cell wall is not a silver bullet to dehydration stress or fungal pathogens. Even so, the results of this study help to further our understanding of the role of the cell wall as a physical barrier to both abiotic and biotic stresses.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/plants11030385/s1. Figure S1: Generalized additive models showing the relationship between temperature (◦C) and pectin viscosity (Pa.S), Figure S2: Analysis of green pixels from images obtained from *Allium fistulosum* epidermal cell layers stained with fluorescein diacetate, Figure S3: Analysis of green pixels from images obtained from *Allium cepa* epidermal cell layers stained with fluorescein diacetate; Table S1: Primers used to genotype *nip5;1-1*, *nip6;1-2* and *bor1-3*, Table S2: ANOVA for generalized additive models examining the relationship between temperature (◦C) and pectin viscosity (Pa.S), Table S3: ANOVA analyzing the force required to shear *Allium fistulosum* sheaths, Table S4: ANOVA analyzing percent water loss in *Allium fistulosum* and *Allium cepa* sheaths, Table S5: ANOVA analyzing percent water loss in pectin solutions, Table S6: Tukey's test analyzing percent water loss in pectin solutions, Table S7: ANOVA examining percent viability based on electrolyte leakage following dehydration in *Allium fistulosum* and *Allium cepa*, Table S8: Two-sample *t*-tests analyzing the intensity of green pixels following staining with fluorescein diacetate in *Allium fistulosum* and *Allium cepa*, Table S9: ANOVA analyzing lesion size following *Botrytis cinerea* inoculation in *Arabidopsis*, Table S10: Tukey test analyzing lesion size following *Botrytis cinerea* inoculation in *Arabidopsis*, Table S11: ANOVA analyzing lesion size following *Colletotrichum higginsianum* inoculation in *Arabidopsis*, Table S12: Tukey test analyzing lesion size following *Colletotrichum higginsianum* inoculation in *Arabidopsis*.

**Author Contributions:** Conceptualization, K.K.T.; methodology, K.K.T., C.K., Y.Z.F., S.G. and Y.W.; software, A.D.F., M.L. and J.S.; formal analysis, A.D.F., M.L. and J.S.; investigation, A.D.F., Y.Z.F., S.W. and K.K.T., resources, K.K.T., Y.W., L.Q. and S.G.; data curation, A.D.F., M.L. and J.S.; writing original draft preparation, A.D.F. and K.K.T.; writing—review and editing, A.D.F. and K.K.T.; visualization, K.K.T.; supervision, K.K.T., C.K., Y.Z.F., S.G. and Y.W.; project administration, K.K.T.; funding acquisition, K.K.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Alexander Graham Bell Canadian Graduate Scholarship-Masters (CGS-M) from the National Science and Engineering Research Council (NSERC) of Canada awarded to A.D.F, in addition to an NSERC Discovery grant awarded to K.K.T (RGPIN-2018-05853).

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data supporting the above findings are available within this paper and Supplementary Materials published online.

**Acknowledgments:** We thank Fatemeh Keivaninahr and Chi Diem Doan (University of Saskatchewan (USask), Canada) for their assistance with the rheometer and Phyllis Shand (USask, Canada) for her help with texture analysis, Na Liu (Canadian Light Source, Canada) for assistance with sample preparation for the synchrotron and Eric Lamb (USask, Canada) for guidance related to generalized additive models. We would also like to acknowledge Keristein Muller (Veristat, Canada) for the p35S::PMEI5 line and Hong Wang (USask, Canada) for assistance in ordering primers. Eldon Siemens (Agriculture Greenhouse, USask, Canada) in addition to other greenhouse staff were instrumental in the growth of Allium plants. We acknowledge fellow lab members Ian Willick and Eric Rae for support and assistance in the project. Finally, we acknowledge the University of Saskatchewan for their generosity, as this work was supported in part by various scholarships and bursaries. Part of the research described in this paper was performed at the Canadian Light Source, a national research facility of the University of Saskatchewan, which is supported by the Canada Foundation for Innovation (CFI), the Natural Sciences and Engineering Research Council (NSERC), the National Research Council (NRC), the Canadian Institutes of Health Research (CIHR), the Government of Saskatchewan, and the University of Saskatchewan. This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory and was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357, and the Canadian Light Source and its funding partners.

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