Preparation of Seaweed Nanopowder Particles Using Planetary Ball Milling and Their Effects on Some Secondary Metabolites in Date Palm (Phoenix dactylifera L.) Seedlings

Due to their distinctive physicochemical characteristics, nanoparticles have recently emerged as pioneering materials in agricultural research. In this work, nanopowders (NP) of seaweed (Turbinaria triquetra) were prepared using the planetary ball milling procedure. The prepared nanopowders from marine seaweed were characterized by particle size, zeta potential, UV-vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). When the seaweed nanopowder of Turbinaria triquetra was subjected to FT-IR analysis, it revealed the presence of different functional groups, including alkane, carboxylic acids, alcohol, alkenes and aromatics. Moreover, the methanol extract was used to identify the polyphenolic components in seaweed (NP) using high performance liquid chromatography (HPLC) and the extract revealed the presence of a number of important compounds such as daidzein and quercetin. Moreover, the pot experiment was carried out in order to evaluate the effects of prepared seaweed (NP) as an enhancer for the growth of date palm (Phoenix dactylifera L.). The date palm seedlings received four NP doses, bi-distilled water was applied as the control and doses of 25, 50 or 100 mg L−1 of seaweed liquid NP were used (referred to as T1, T2, T3 and T4, respectively). Foliar application of liquid NP was applied two times per week within a period of 30 days. Leaf area, number of branches, dry weight, chlorophylls, total soluble sugars and some other secondary metabolites were determined. Our results indicated that the foliar application of liquid NP at T3 enhanced the growth parameters of the date palm seedlings. Additionally, liquid NP at T3 and T4 significantly increased the photosynthetic pigments. The total phenolic, flavonoid and antioxidant activities were stimulated by NP foliar application. Moreover, the data showed that the T3 and T4 doses enhanced the activity of the antioxidant enzymes (CAT, POX or PPO) compared to other treatments. Therefore, the preparation of seaweed NP using the planetary ball milling method could produce an eco-friendly and cost- effective material for sustainable agriculture and could be an interesting way to create a nanofertilizer that mitigates plant growth.