## 4 Discussion  
In the present paper, algae bio-products were obtained by their homogenization. Mechanical processing of macroalgae avoids the use of organic solvent, acid or alkali to produce extracts with properties that are significantly different from products obtained by chemical methods [34; 35]. Therefore, these products are safe for application in agriculture. In the present study we examined the multi-elemental composition of raw algae biomass, as well as the obtained filtrate and homogenate. Algal products are rarely studied in terms of the content of elements. The results showed that the tested products can be a source of micro- and macro-elements in plant cultivation, especially algal homogenate that was rich in B, Fe, Mn, Zn, K, P, and S in contrary to algal filtrate. The results from the present study were compared with multi-elemental composition of algal extract obtained from the same algae using microwave assisted extraction (MAE) [30] and chemical hydrolysis with acidified water (pH 2) [36]. It was found that especially micro-elements were extracted more efficiently using mechanical processing than the mentioned physico-chemical methods. The filtrate and homogenate were also examined in terms of their ability to complex Zn(II) ions. It was assumed, that algal products enriched with microelement ions can be used as liquid fertilizers or organic fertilizers/soil amendments that will supply plants with a highly bio-available form of elements. It was shown that the amount of Zn(II) ions complexed by homogenate was higher than by filtrate. This can result from the physical form of the examined products (solid residue and liquid). Algal homogenate may contain many more macromolecules, such as polysaccharides (e.g., ulvan in green seaweeds) rich in functional groups capable of binding micronutrient ions in a reversible process [37]. Usually, as it is reported in the literature, the chelating properties of algal extracts are tested for ferrous ions when the antioxidant properties of extracts were examined [10]. The aim of the present study was also to examine the utilitarian properties of algal homogenate and filtrate in the tests on radial. We studied the effect of the method of application of algal filtrate (soil and foliar), as well as the effect of seed treatment with algal filtrate and homogenate (seed soaking and coating, respectively) on the length, weight, and multi-elemental composition of seedlings. In the literature, there are some papers that describe the effect of algal products obtained by mechanical processes on plant growth. [PERSON] et al. (2010) examined the effect of 15% algal filtrate obtained from green macroalgae _Ulva ferticulata_ and _Chaetomorpha_ sp., by homogenization in a blender, on the growth and yield of rice plants. Seaweed extract treatment was done by spraying the whole plant. The examined extracts did not give positive response to the rice plant height or the weight of stems and roots, but influenced the number of leaves, tilters, and the weight of rice panicle [21]. [PERSON] et al. (2014) used a seaweed filtrate from _Ascophyllum nodosum_ (produced after micro-grinding, flocculation, and filtration) in greenhouse trials on lettuce. The addition of filtrate directly to the irrigation water increased the lettuce shoot dry weight [1]. [PERSON] and [PERSON] (2012) indicated that depending on the application method of biostimulants, different effects on plants can be observed, for example the drenching application method enhances the stem height, whereas foliar application increases the flower buds number and promotes the fresh weight of bulb roots [38]. In our research, it was found that better results in terms of seedlings' length were obtained for soil application of algal filtrate (50%) than foliar (by 21% longer). Soil application of algal extracts is known to improve shoot growth, root development, and mineral absorption [4].