Seed Priming with Zinc Oxide Nanoparticles and/or Calcium Ion: Alleviation Potential for Salt Toxicity in Tomato (Solanum lycopersicum) through Modulation of Physiochemical Attributes and Antioxidant Enzyme Activity

This study assesses how zinc oxide nanoparticles (ZnO-NPs) and calcium chloride (CaCl2), affect the physiology and growth of tomato (Solanum lycopersicum L.) under salt (NaCl) stress. Before sowing, tomato seeds were soaked in 100 mM of ZnO-NPs and 2 mM of CaCl2 for 12 h alone and in combination with 100 mM of NaCl. The findings showed that salinity stress had an adverse effect on tomato plant growth and physiology by reducing photosynthesis, fresh and dry weight, and the SPAD value of chlorophyll, carbonic anhydrase (CA), nitrate reductase (NR) while increasing the activity of antioxidant enzymes, hydrogen peroxide (H2O2), malondialdehyde (MDA), proline, and other chemicals that are directly linked to increased oxidative stress. Pre-treatment of ZnO-NPs and CaCl2 alleviated the negative effects of salinity on tomato plants, as indicated by improving these attributes. Seed soaking treatments of ZnO-NPs and CaCl2 was found efficient in improving the length, fresh and dry weight, photosynthesis, transpiration rate, total carbohydrate and reducing sugar in tomato plants under salinity stress. Beside, ZnO-NPs and CaCl2 decreased the NaCl-induced oxidative stress by declining proline, Na+, and Na+/K+ contents. Thus, our research showed that ZnO-NPs are more efficient and advantageous than CaCl2 in encouraging tomato plant growth and mitigating the negative impacts of NaCl stress.