This review presents a comprehensive and systematic study of the field of plant biostimulants and considers the fundamental and innovative principles underlying this technology. The elucidation of the biological basis of biostimulant function is a prerequisite for the development of science-based biostimulant industry and sound regulations governing these compounds. The task of defining the biological basis of biostimulants as a class of compounds, however, is made more complex by the diverse sources of biostimulants present in the market, which include bacteria, fungi, seaweeds, higher plants, animals and humate-containing raw materials, and the wide diversity of industrial processes utilized in their preparation. To distinguish biostimulants from the existing legislative product categories we propose the following definition of a biostimulant as ‘a formulated product of biological origin that improves plant productivity as a consequence of the novel or emergent properties of the complex of constituents, and not as a sole consequence of the presence of known essential plant nutrients, plant growth regulators, or plant protective compounds’. The definition provided here is important as it emphasizes the principle that biological function can be positively modulated through application of molecules, or mixtures of molecules, for which an explicit mode of action has not been defined. Given the difficulty in determining a ‘mode of action’ for a biostimulant, and recognizing the need for the market in biostimulants to attain legitimacy, we suggest that the focus of biostimulant research and validation should be upon proof of efficacy and safety and the determination of a broad mechanism of action, without a requirement for the determination of a specific mode of action. While there is a clear commercial imperative to rationalize biostimulants as a discrete class of products, there is also a compelling biological case for the science-based development of, and experimentation with biostimulants in the expectation that this may lead to the identification of novel biological molecules and phenomenon, pathways and processes, that would not have been discovered if the category of biostimulants did not exist, or was not considered legitimate.

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Biostimulants in Plant Science: A Global Perspective.

Titanium (Ti) is considered a beneficial element for plant growth. Ti applied via roots or leaves at low concentrations has been documented to improve crop performance through stimulating the activity of certain enzymes, enhancing chlorophyll content and photosynthesis, promoting nutrient uptake, strengthening stress tolerance, and improving crop yield and quality. Commercial fertilizers containing Ti, such as Tytanit and Mg-Titanit, have been used as biostimulants for improving crop production; however, mechanisms underlying the beneficial effects still remain unclear. In this article, we propose that the beneficial roles Ti plays in plants lie in its interaction with other nutrient elements primarily iron (Fe). Fe and Ti have synergistic and antagonistic relationships. When plants experience Fe deficiency, Ti helps induce the expression of genes related to Fe acquisition, thereby enhancing Fe uptake and utilization and subsequently improving plant growth. Plants may have proteins that either specifically or nonspecifically bind with Ti. When Ti concentration is high in plants, Ti competes with Fe for ligands or proteins. The competition could be severe, resulting in Ti phytotoxicity. As a result, the beneficial effects of Ti become more pronounced during the time when plants experience low or deficient Fe supply.

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Titanium as a Beneficial Element for Crop Production

Field and laboratory experiments were carried out in 2012–2013, aimed at evaluating the influence of new products stimulating plant growth based on amino acids on crop yield, characteristics of grain and content of macro- and micronutrients in winter wheat (Triticum aestivum L.). The tests included two formulations produced in cooperation with INTERMAG Co. (Olkusz, Poland)—AminoPrim and AminoHort, containing 15% and 20% amino acids, respectively, and 0.27% and 2.1% microelements, respectively. Field experiments showed that the application of products based on amino acids influenced the increase of grain yield of winter wheat (5.4% and 11%, respectively, for the application of AminoPrim at a dose 1.0 L/ha and AminoHort at dose 1.25 L/ha) when compared to the control group without biostimulant. Laboratory tests showed an increase of technological characteristics of grain such as ash content, Zeleny sedimentation index and content of protein. The use of the tested preparations at different doses also contributed to the increase of the nutrients content in grains, in particular copper (ranging 31–50%), as well as sodium (35–43%), calcium (4.3–7.9%) and molybdenum (3.9–16%). Biostimulants based on amino acids, tested in the present study, can be recommended for an efficient agricultural production.

https://www.mdpi.com/1420-3049/23/2/470/pdf

Effect of the New Plant Growth Biostimulants Based on Amino Acids on Yield and Grain Quality of Winter Wheat.

This paper presents a research review of the effect of silicon fertilization on the yield quantity and quality in the last 15 years. The study focuses on plant species grown in Europe: cereals, soybean, rapeseed, sugar beet, potato, meadows, berries and vegetables, and orchard and ornamental plants. The use of silicon is most common in the production of vegetables in greenhouses. However, the use of this element for the fertilization of agricultural plants is rare. Positive prospects of silicon fertilization are associated with foliar application, which is much cheaper and more convenient to use than soil fertilization. Foliar application of silicon has a biostimulative effect, and the best results are observed in stressful conditions for plants such as salinity, deficiency or excess of water, high and low temperature, and the strong pressure of diseases and pests, etc. Based on the results of previous studies, it can be concluded that foliar nutrition should be introduced into production as a standard treatment in the crop management of many species of agricultural plants. It can help farmers to increase the yield of crops. It is also important that it is safe for the environment, which is particularly important in Europe.

Effect of Silicon Fertilization on Crop Yield Quantity and Quality-A Literature Review in Europe.

Oxidative stress is the consequence of an imbalance of pro-oxidants and antioxidants leading to cell damage and tissue injury. The exhaustion of antioxidant systems is one of the reasons for the occurrence of oxidative stress, which results in avalanche production of reactive oxygen species (ROS) or free radicals. High oxidative stress is common in organs and tissues with high metabolic and energy demands, including skeletal and heart muscle, liver and blood cells. Stress arises in animals in response to unavoidable or adverse environmental conditions. In the external environment, which affects the body of the cow, there are four main groups of stressors: physical, chemical, biological and psychological. Physical stressors include fluctuations in ambient temperature as well as mechanical injuries. High ambient temperature is one of the factors affecting the productivity of cows. Biological stressors are conditioned by errors and irregularities in habits. Both of these phenomena have an adverse impact on both the resistance of animals and fertility and are the etiological agent of oxidative stress. Various mechanisms may be responsible for metal-induced oxidative stress: direct or indirect generation of ROS, depletion of glutathione and inhibition of antioxidant enzymes are well known for all redox-active and redox-inactive metals.

The etiology of oxidative stress in the various species of animals, a review.

Effects of silicon foliar fertilization of meadow plants on the nutritional value of silage fed to dairy cows

The experiment was conducted during 2010–2012 on a private farm in the Slaskie province, at an altitude of 320 m above sea level. A one-factorial field experiment was set up as a randomized block design with four replications. The experimental plots, 10 m in area, had class V acid brown soil. Treatment factors were spraying three concentrations (0.02, 0.04 and 0.08 %) of growth biostimulant (Tytanit fertilizer). The highest dose of the foliar application of Tytanit (0.08 %) caused significant increases in dry matter yield and nutrient content in relation to the control plot. The protein and energy value was also found to increase significantly. Satisfactory results were also obtained in plots where titanium was applied at a concentration of 0.04 %.

Effect of Foliar Application of Growth Biostimulant on Quality and Nutritive Value of Meadow Sward

Abstract Titanium is one of a plant biostimulators. It stimulates life processes, growth and development, as well as affects physiological and biochemical pathways, often increasing biomass production and enhancing yield. An open field experiment was conducted in the years 2011-2013 in Polanowice, Poland to investigate the effects of titanium foliar fertilization on the growth of timothy grass (Phleum pratense L.). This single-factor, randomized block design study was performed in four replicates on research plots with the area of 10 m2 each. The substrate was black loess soil (chernozem) typical for top class farmland. Titanium fertilization via leaf spray was performed with a water solution of Tytanit® at three doses of 0.2, 0.4, and 0.8 dm3 · ha−1. Foliar fertilization with the highest dose of Tytanit® significantly increased seed yield, thousand grain weight and germination capacity. Moreover, the middle dose of Tytanit® (0.4 dm3 · ha−1) was enough to observe a positive effect on the sample.

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Effects of Foliar Application of Titanium on Seed Yield in Timothy (Phleum pratense L.)

Abstract A field experiment was conducted in the years 2012-2014, at the Plant Breeding Station in Polanowice near Krakow (220 m a.s.l.). The aim of the study was to investigate the effect of silicon (Si) on seed yield and quality of timothy-grass (Phleum pratense L.) of “Egida” cultivar. A univariate field experiment in randomized block design was repeated four times, and the area of the experimental plots was 10 m2. The soil on the experimental plots was a loess derived haplic phaeozem of bonitation class I. The experimental factor was spraying with a silicon formulation in the form of Optysil® fertilizer at three doses: 0.2, 0.5 and 0.8 dm3·ha−1. During the growing season, the plants were evaluated for their height, leaf greenness index (SPAD) and general condition. After harvesting, the seed yield and quality were assessed. The study revealed a significant effect of silicon on plant height, general condition and yield and quality of the seeds. The plants treated with silicon showed lower infestation rate with pathogens and pests than the control ones. Foliar fertilization with the highest dose of the silicon formulation (0.8 dm3·ha−1) caused a significant increase in seed yield as compared with control. The effects were also satisfactory in the plants treated with the formulation at 0.5 dm3·ha−1. The seeds obtained from silicon-treated plants were bigger, as revealed by the weight of 1000 seeds, and exhibited higher germination ability than the control seeds.

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Effects of silicate fertilizer on seed yield in timothy-grass (Phleum pratense L.)

The purpose of this research was to assess the functional value of the “Super Trawnik” lawn mixture. The studies were carried out between 2017 and 2019 at the Experimental Station of the University of Agriculture in Krakow (50°07′ N, 20°05′ E), and the experimental factor was the AGRO-SORB® Folium, a biostimulant containing amino acids and applied at three doses: 1, 2, and 3 L·ha−1. Lawn visual quality was assessed on a 9-point scale, with 10–11 mowings at 4 cm during the growing period. An increase in the concentration of the stimulant applied as a spray resulted in a significant increase in its effectiveness; plants in plots with the highest dose of amino acid solution (Variant III) had the highest aesthetic and functional values. The AGRO-SORB® Folium reduced the occurrence of fungal diseases; compared to control plants, there was a 16% reduction of Fusarium patch (Microdochium nivale) infection and a 20% reduction of Dreschlera leaf spot (Drechslera siccans). Satisfactory effects were also recorded on plots where the product was applied at a dose of 2 L·ha−1 (Variant II). Those plots had more favourably rated turf, with higher resistance of plants to Fusarium patch by 12% and to Dreschlera leaf spot by 20% compared to control.

https://www.mdpi.com/2073-4395/10/11/1656/pdf

Adam Radkowski

Papers

Effects of silicon foliar fertilization of meadow plants on the nutritional value of silage fed to dairy cows

Effect of Foliar Application of Growth Biostimulant on Quality and Nutritive Value of Meadow Sward

Effects of Foliar Application of Titanium on Seed Yield in Timothy (Phleum pratense L.)

Effects of silicate fertilizer on seed yield in timothy-grass (Phleum pratense L.)

The Effect of Foliar Application of an Amino Acid-Based Biostimulant on Lawn Functional Value