Remediation of pear iron chlorosis by nanocellulose-iron chelation and mechanisms

Abstract Background: Nanocrystal cellulose has a strong ability to chelate iron and the nanocomposite possesses strong adsorptive property. Iron deficiency chlorosis (IDC) is a mineral disorder that weakens pear photosynthesis and cause a significant decline in plant yield and quality. Conventional methods to control IDC are generally due to low efficiency and overuse of chemicals. The purpose of this study was to explore the capability of nanocellulose (NC)-Fe chelate to remediate pear IDC. Acidic hydrolyzed NCs were chelated with Fe (NCFe) based on the net charge density of the components. Foliar application of NCFe was employed to pre-etiolated seedlings of Pyrus betulifolia as a plant material. The ability of NCFe to promote active iron content (CFe), photosynthesis rate, and relative gene expression was studied. Results: Nanocrystal cellulose prepared by acidic hydrolysis exhibit rod-like whiskers carrying on negative charges. When NCs were mixed with FeSO4, the NCFe particles maintained a small, whisker-like morphology with small dots (Fe) on the surface of the NC particles. The Z-average hydrodynamic diameter and zeta potential of the NC whiskers measured by DLS were 84.3 ± 0.2 nm and -47.3 ± 1.7 mV, respectively. The particle size and zeta potential of NCFe were 107.4±3.0 nm and -9.7±0.4 mV, respectively. The results showed that NCFe could significantly mitigate IDC in seedlings by increasing CFe, photosynthesis parameters, major physiological indicators, and regulating the expression of key enzymes. When NCFe was prepared at a NC-to-Fe charge density ratio of 1:3,000, CFe and chlorophyll contents were enhanced by approximately 9 times and 72.7%, respectively; the major physiological indicators were all significantly increased. Interestingly, NCFe treatment significantly downregulated the expression of the pectin methylesterase gene (PbPME) and upregulated the expression of the ferritin gene (PbFER) to increase CFe.Conclusion: NCs have strong potential to promote plant photosynthesis when chelated with Fe. The remediation capability of NCFe to IDC is attributed to the enhancement of photosynthesis parameters and indicators. NCFe treatment significantly downregulated the expression of the PME gene (PbPME) and upregulated the expression of the ferritin gene (PbFER) to increase the active iron content. This finding will provide a good alternative and a complementary strategy for Fe-chelate applications in plant iron chlorosis management.