Proline doped ZnO nanocomposite alleviates NaCl induced adverse effects on morpho-biochemical response in Coriandrum sativum

•Proline was doped on chemically synthesized ZnO nanoparticles.•Coriander plants were grown in presence of NaCl and synthesized material.•Plant morphological response significantly improved by nanocomposite.•Oxidative stress and antioxidants level in plants decreased by ZnO-proline NPs.•ZnO-proline NPs can be applied as nanofertilizer to mitigate abiotic stress. Salinity stress is a major abiotic factor causing destructive impact on plant growth. Therefore, an approach is needed to alleviate the negative effect of salinity stress. Considering the distinct and advantageous effects of proline and zinc oxide nanoparticles (ZnO NPs) on plant growth, ZnO NPs were functionalized by proline (ZnOP NPs) under the concept of nanofertilizer and slow release of molecules. An in vitro study was performed to investigate the effect of nanocomposite on Coriandrum sativum (coriander) exposed to 50 mM NaCl stress. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed 14.73 nm and 20.59 nm size of ZnO NPs and ZnOP NPs, respectively with spherical to hexagonal structures. Vegetative parameters of plants like height and biomass were improved by the application of NPs. ZnOP NPs at 100 mg/L depicted 200% increase in shoot length while 157% increase in root length when applied with NaCl stress. Fresh weight of shoots and roots increased upto 387 mg and 127 mg, respectively at 100 mg/L ZnOP NPs. Antioxidant and phytochemical activities that were increased due to salinity stress, decreased by ZnOP NPs. Radical scavenging activity reduced upto 55%, antioxidant potential upto 35%, and reducing power by 20% in shoots of plants as compared to NaCl stressed plants. A similar trend was also observed in roots. Likewise, phenolic content decreased by 30% in shoots and 43% in roots at 100 mg/L of ZnOP NPs and same for flavonoid contents. Application of ZnOP NPs to salt stressed plants also reduced the concentrations of superoxide dismutase (SOD) and peroxide dismutase (POD). In conclusion, proline functionalized ZnO NPs were proved effective against salinity stress. This nanofertilizer can be promoted as a potential candidate for combating the negative effects of saline condition.