Zinc Oxide Nanoparticle Sustain Photosystem II Functionality and Specific Energy Fluxes in Two Cereal Crops under Hyper-Saline Environment

Nanotechnology is an emerging tool which has the potential to stimulate photosynthetic process in stress related environment. Unfortunately, the role of nanotechnology on photosynthetic performance explaining photosystem II functionality and specific energy fluxes in crop plants are rather scarce. Photosystem II contributes 90% of the energy requirement in plants, therefore its participation in a sub-optimal environment cannot be ruled out. The current study not only elucidates the role of Zinc-NP on light harvesting efficiency of photosystem II and specific energy fluxes but also explains their subsequent involvement in physiological tolerance against salt stress in saline soil. Oryza sativa L. rice var. Diamond and Triticum aestivum L.wheat var. Benazir seeds were sown in plastic pots and were allowed to grow in natural condition. Fifteen-day-old plants were exposed to ZnO-NP at 0.02 g/L with or without salt stress (0, 75, and 150 mM) NaCl concentration. Application of nanoparticles in saline environment showed 22 to 36% increase in rice and 9 to 25% in wheat growth. Biomass accumulations and relative water content (RWC) were also increased from 10 and 111% in a suboptimal condition. Moreover, nanoparticles reduced the oxidative damages in both rice and wheat plants indicating –20.2 to –58.3% and −28.7 to –20.2% reduction in the MDA and H2O2 production under moderate to severe salt stress. Maximum quantum yield (Fv/Fm) was less affected in severe and moderate salt stress indicating –7 and –5.4% decrease in stress condition. Foliar application of ZnO-NP improves the size and number of active reaction centre of photosynthetic machinery (Fv/Fo) and performance index (PIabs) in saline soil. It was concluded that Zn-NP not only sustained light harvesting potential in both cereal plants under salinized soil but also increases the biomass accumulation and reduces oxidative damage in a sub-optimal environment.