Destructive effect of copper oxide nanoparticles on ultrastructure of chloroplast, plastoglobules and starch grains in spring barley (Hordeum sativum)

Abstract

This study focused on determining the phytotoxic mechanism of copper oxide nanoparticles (CuO-NPs); destroying chloroplasts, plastoglobules and starch granules in spring barley (Hordeum sativum distichum) leaves. Recently, plastoglobule emerged as an important role player in chloroplast lipid metabolism operating as a thylakoid microdomain for metabolite synthesis, repair, and disposal. In the past few decades, application of NPs in agriculture has increased drastically which imposed the threat on crops by damaging xylem vessels and photosynthetic apparatus. The study was performed on spring barley grown in a hydroponic condition, supplemented with a high concentration of CuO-NPs to observe the toxicity on the ultrastructure of chloroplasts, plastoglobules and starch granules. The ultrathin cross sections of spring barley leaves revealed that the NPs decreased the counts of plastoglobule and starch granule on chloroplast. However, the size of plastoglobule and chloroplast increased in comparison to control. In addition, swollen starch granules and scattered thylakoids were also found. This is the first detailed study of NPs toxicity on the crop plants. The results indicated that the chloroplast could be as one of the important characteristics in the evaluation of NPs toxicity on plants.