A pot experiment was conducted during the 2019/2020 and 2020/2021 seasons to evaluate the effect of silver nanoparticles (SNPs), iron nanoparticles (FeNPs), zinc nanoparticles (ZnNPs), and nitrogen, phosphorus, and potassium nanoparticles (NPK NPs) and humic acid (HA) in improving the growth of Philodendron plants. Our findings indicated that the highest increase in plant height and leaf width was recorded with 60 mg/L SNPs. Additionally, the highest values in the number of leaves plant−1 were

more »

... ecorded with 60 mg/L SNPs compared to the control. FeNPs at 150 mg/L treatment gave the best result of total chlorophyll and carotenoid content, followed by SNPs at 60 mg/L and then NPK NPs at 2 mL/L in the two seasons. Furthermore, ZnNPs at 200 mg/L, SNPs at 20 mg/L, SNPs at 40 mg/L, and SNPs at 60 mg/L gave the best results of enzyme activity (catalase, peroxidase, and polyphenol oxidase). However, the treatments with 40 and 60 mg/L SNPs led to improve the anatomical characters of leaves and stem such as thickness of the blade, mesophyll tissue, xylem vessel diameter, vascular bundle dimension, stem diameter, and epidermis cell dimension compared with other treatments and the control.