Abstract
The aim of the present work was to investigate the toxic effects of zinc oxide nanoparticles (ZnO NPs, particle size < 50 nm) on the physiological and anatomical indices of spring barley (Hordeum sativum L.). The results show that ZnO NPs inhibited H. sativum growth by affecting the chlorophyll fluorescence emissions and causing deformations of the stomatal and trichome morphology, alterations to the cellular organizations, including irregularities of the chloroplasts, and disruptions to the grana and thylakoid organizations. There was a lower number of chloroplasts per cell observed in the H. sativum leaf cells treated with ZnO NPs as compared to the non-treated plants. Cytomorphometric quantification revealed that ZnO NPs decreased the size of the chloroplast by 1.5 and 4 times in 300 and 2000 mg/L ZnO NP-treated plants, respectively. The elemental analysis showed higher Zn accumulation in the treated leaf tissues (3.8 and 10.18-fold with 300 and 2000 mg/L ZnO NPs, respectively) than the untreated. High contents of Zn were observed in several spots in ZnO NP-treated leaf tissues using X-ray fluorescence. Deviations in the anatomical indices were significantly correlated with physiological observations. The accumulation of Zn content in plant tissues that originated from ZnO NPs was shown to cause damage to the structural organization of the photosynthetic apparatus and reduced the photosynthetic activities.
Highlights
The application of nanoparticles (NPs) in agriculture was accepted at the beginning of the 21st century [1], and more than 231 products are available for various agricultural applications (https://product.statnano.com/)
The properties of the zinc oxide (ZnO) NPs were characterized by transmission electron microscopy (TEM; Tecnai G12, FEI Company, Czech Republic), powder X-ray diffraction was used to estimate the crystalline sizes, and their stability was analyzed using dynamic light scattering (DLS) and ζ-potential measurements
The TEM observations showed that the NPs consisted of hexagonal lamellar particles with a major axis of 50–150 nm and a minor axis of 20–70 nm (Figure 1a,b)
Summary
The application of nanoparticles (NPs) in agriculture was accepted at the beginning of the 21st century [1], and more than 231 products are available for various agricultural applications (https://product.statnano.com/ (accessed on 15 March 2021)). Zinc-based NPs are among the most widely used NPs in the nanoindustry [4], and are produced (550–5550 t a−1 ) 10 to 100 times more than the other NPs [5,6]. They are extensively utilized in the cosmetics industry [7], medicines [8], food, and solar cells [9], which inevitably leads to their transfer to the environment [10]. Due to their ability to absorb and accumulate pollutants, plants play a crucial role in this transfer, especially in the food chain [11]
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