Gas Exchange Parameters, Fruit Yield, Quality, and Nutrient Status in Tomato Are Stimulated by ZnO Nanoparticles of Modified Surface and Morphology and Their Application Form

Nanoparticles (NPs) of ZnO are reported to enhance plant growth; however, during NPs syntheses, they tend to agglomerate, affecting their dispersion. Agglomeration can be counteracted if NPs surface is modified and/or they have the appropriate morphology. The objective of the present study was to assess the effects of the morphology, the surface modification, and the way of application of NPs-ZnO on tomato. Two NPs-ZnO morphologies (spherical or hexagonal) whose surface was modified with maltodextrine (MDX) or not, and applied to tomato plants via foliar sprays or drench at 1500 ppm were assessed. Hexagonal and spherical NPs increased plant growth, and fruit yield, quality and nutrient status, and gas exchange parameters. Fruit P, K, Ca, Mg, Mn, and Si were higher when hexagonal NPs-ZnO modified with MDX were applied by drench; however, Zn was higher when spherical or hexagonal no surface modified NPs were applied. The morphology of NPs, alone or combined with foliar or drench applications, did not affect fruit yield or quality. MDX applied alone increased fruit yield and quality. Nanoparticles of ZnO increased growth and yield, although spherical or hexagonal NPs produced similar results. Hexagonal nanoparticles applied by drench increased biomass when their surface was modified with MDX; however, even though fruit yield was not affected, drench applications of MDX-modified hexagonal NPs resulted favorable for macronutrient and Mn and Si status in the fruits. MDX had a biostimulant effect as it increased yield, quality of fruits, photosynthesis, transpiration, and nutrients status in fruits.