Modification of Tomato Photosystem II Photochemistry with Engineered Zinc Oxide Nanorods

Abstract

We recently proposed the use of engineered irregularly shaped zinc oxide nanoparticles (ZnO NPs) coated with oleylamine (OAm), as photosynthetic biostimulants, to enhance crop yield. In the current research, we tested newly engineered rod-shaped ZnO nanorods (NRs) coated with oleylamine (ZnO@OAm NRs) regarding their in vivo behavior related to photosynthetic function and reactive oxygen species (ROS) generation in tomato (Lycopersicon esculentum Mill.) plants. ZnO@OAm NRs were produced via solvothermal synthesis. Their physicochemical assessment revealed a crystallite size of 15 nm, an organic coating of 8.7% w/w, a hydrodynamic diameter of 122 nm, and a ζ-potential of −4.8 mV. The chlorophyll content of tomato leaflets after a foliar spray with 15 mg L−1 ZnO@OAm NRs presented a hormetic response, with an increased content 30 min after the spray, which dropped to control levels 90 min after the spray. Simultaneously, 90 min after the spray, the efficiency of the oxygen-evolving complex (OEC) decreased significantly (p < 0.05) compared to control values, with a concomitant increase in ROS generation, a decrease in the maximum efficiency of PSII photochemistry (Fv/Fm), a decrease in the electron transport rate (ETR), and a decrease in the effective quantum yield of PSII photochemistry (ΦPSII), indicating reduced PSII efficiency. The decreased ETR and ΦPSII were due to the reduced efficiency of PSII reaction centers (Fv’/Fm’). There were no alterations in the excess excitation energy at PSII or the fraction of open PSII reaction centers (qp). We discovered that rod-shaped ZnO@OAm NRs reduced PSII photochemistry, in contrast to irregularly shaped ZnO@OAm NPs, which enhanced PSII efficiency. Thus, the shape and organic coating of the nanoparticles play a critical role in the mechanism of their action and their impact on crop yield when they are used in agriculture.

Mechanistic Approach on Melatonin-Induced Hormesis of Photosystem II Function in the Medicinal Plant Mentha spicata

“…When the OEC fails to efficiently reduce the chlorophyll molecule at the PSII RC, it results in damaging oxidations in PSII [59]. Consequently, donor-side photoinhibition is often associated with the production of ROS [55,[62][63][64]. The minor increase in ROS generation that we observed (Figure 7c), as a result of donor-side photoinhibition (Figure 2b), can be attributed to a malfunction of the OEC (Figure 2a).…”

Zinc oxide and copper oxide nanoparticles as a potential solution for controlling Phytophthora infestans, the late blight disease of potatoes

“…The ROS produced may include hydroxyl radicals (OH•), superoxide ions (O2•), and singlet oxygen (1O2), which induce lipid peroxidation and ultimately result in cell death [ 17 ]. Tryfon et al [ 79 ] demonstrated that the synthesized ZnO@OAm NRs resulted in a decrease in the efficiency of the oxygen-evolving complex (OEC), accompanied by an increase in reactive oxygen species (ROS) generation and reduced Photosystem II (PSII) photochemistry efficiency.…”