New Discovery Of Biostimulants – “SF-Pollen Polysaccharide”
Extracted From Pollen, With Multiple Functions and High Activity
By: Huang Jin, Wu Dan, Wang Shuai
1 – Research Background of Biostimulants
Agriculture has brought stable food to mankind and enabled human civilization to develop by leaps and bounds. However, with the development of human society, the world agriculture and food security are facing unprecedented challenges. It is expected that the world hunger crisis will rise by 30% in 2050 [1]. In recent years, the global intensive agriculture has ensured food production and food safety to a certain extent by increasing agricultural inputs including chemical pesticides and synthetic fertilizers, but also caused irreversible environmental degradation and depletion of non-renewable resources. Therefore, Biostimulants, a kind of environmentally friendly, safe and efficient new green agricultural inputs, have gradually entered the vision of professionals in the field of agricultural research and commercialization. Through Biostimulants, crop Nutrient Use Efficiency (NUE) can be improved to reduce chemical input in intensive agriculture and maintain high productivity [2].
1.1 Definition of Biostimulants
The concept of biostimulants can be traced back to Professor V. P. Filatov, who called all biological substances that can affect the metabolism and energy conversion of humans, animals and plants as biological stimulants, further limited the concept of biological stimulants to the application of plants, and considered that organic acids belong to the category of biological stimulants [3]. In the following decades, researchers carried out in-depth research on biostimulants and constantly expanded their depth and outer edge. Finally, the European Biostimulants Industry Council (EBIC) made a clear definition of Plant Biostimulants in 2012: Plant biostimulants means a material which contains substance(s) and/or microorganisms whose function, when applied to plants or the rhizosphere, is to stimulate natural processes to enhance/benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, and crop quality, independent of its nutrient content. [4-5]. Biostimulants do not directly act on insects and diseases, so they do not belong to the scope of pesticide management. The definition of EBIC has clearly pointed out that biostimulants do not contain essential mineral elements of plants, known plant hormones or disease resistance factors, but interact with plant signal transduction processes to reduce the impact of stress on plant growth (Fig. 1). Since then, biostimulants has been favored by major companies around the world as a new agricultural input and has developed rapidly.
The development of Biostimulants in Europe has always been at the forefront of the world. In 2019, the European Union promulgated and implemented the new EU fertilizer product regulation EU 2019 / 1009, which is the first law in the world to classify Biostimulants as agricultural inputs. Since July 16th, 2022, the regulation has been fully implemented. Since then, Biostimulants have been managed in Europe as an independent category under the fertilizer framework. According to the regulation EU 2019 / 1009, Biostimulants are products that do not rely on nutrients to stimulate the process of plant nutrient absorption and utilization. Their sole purpose is to improve one or more of the following characteristics of plants or plant rhizosphere: (1) the plants’ nutrient utilization efficiency; (2) tolerance to abiotic stress; (3) quality traits; (4) availability of limited nutrients in soil or rhizosphere [7].
1.2 Categories of Biostimulants
The Biostimulants originally defined by Professor Filatov mainly refer to various organic acids and their derivatives. With the deepening of the research on biostimulants, the widely accepted biostimulants are mainly divided into six categories: humic acids, amino acids, seaweed extracts, inorganic salts, chitin and its derivatives, microorganisms and their metabolites, and plant extracts [5]. According to different sources, biostimulants can be divided into mineral sources, microbial sources, marine sources and plant sources. The new Regulation EU 2019 / 1009 classifies Biostimulants into microbial sources and non microbial sources according to their sources. Among them, microbial sources biostimulants mainly include arbuscular mycorrhizal fungi (AMF) and Rhizosphere growth promoting bacteria (PGPR) [8]. Non-microbial sources biostimulants mainly include: chitosan (chi), humic acid and fulvic acid (HFA), animal and plant protein hydrolysates (PHS), phosphite (PHI), seaweed extract (SWE), silicon (SI), and plant extract (non-seaweed) [9-11]. Through comprehensive analysis of 180 Biostimulants research reports in the world, it is found that (1) the average additional income of all Biostimulants categories is 17.9%, of which the greatest potential is achieved through soil application; (2) in arid climate and vegetable planting, the use of biostimulants has the greatest impact on yield; (3) Biostimulants can play a more effective role in low organic matter content soil, acidified/saline alkali soil and poor soil [12]. The research results provide a general guide for the development and application of Biostimulants for the preparation developers and growers.
1.3 Botanical Source Biostimulants
Although plant extracts were classified as Biostimulants late [11], they developed rapidly in a short time. Only in 2021, 160 academic papers on plant extract Biostimulants were published, accounting for 36% of the total number of Biostimulants, indicating that the research and application of plant extracts have received extensive attention (Fig. 2). Plant extracts include proteins, sugars, nucleic acids, lipids and other major biological macromolecules, as well as sterols, flavonoids, saponins and other stimulating metabolites. Plant extracts can be widely used in the fields of medicine, health and biological pesticides. For example, artemisinin used for malaria treatment is extracted from the plant Artemisia annua, and its discoverer Tu Youyou won the Nobel Prize in Physiology or Medicine in 2015. For example, the 14-hydroxylated brassinosteroid independently developed by Chengdu Newsun Crop Science Co., Ltd. (hereinafter referred to as “Chengdu Newsun”) is extracted from plant pollen. It is the first natural plant growth regulator and is widely used in agriculture to resist low temperature, drought and increase yield and income. In addition, Chengdu Newsun has been engaged in the research of natural plant source extraction for more than 20 years, with thousands of extracted products and widely used in agriculture and other fields to solve the global biological and abiotic stress problems. Its products mainly include Botanical Biostimulants, Botanical Bio-fungicides, Botanical Bio-insecticides, Botanical Bio-herbicides, Botanical biological control technologies and microbial source technologies. Also, Chengdu Newsun has been engaged in the research of synthetic biology technology to solve the industrialization of plant resources and the content of secondary metabolites of plant resources, and has made remarkable progress.
1.4 Application Value of Botanical Based Biostimulants
The pioneer of Biostimulants, Professor V.P. Filatov pointed out that the juice of stressed plants can stimulate the growth of crops and improve the resistance, indicating that, as early as 1933, he discovered the infinite potential of plant extracts as Biostimulants [3]. Biostimulants extracted from plants have natural affinity and high activity with plants and are more easily absorbed and transported by plants. They can quickly activate signal response and transduction pathways in plants and regulate plant growth and development and stress resistance.
2 – SF Pollen Polysaccharide—New Discovery Of Botanical Source Biostimulant
2.1 Source and Characteristics of SF Pollen Polysaccharide
Pollen is an important germ cell of flowering plants, which not only contains important genetic information, but also contains rich nutritional components. Therefore, pollen is known as “Plant Essence” and “Plant Gold”. SF Pollen Polysaccharide is a botanical source Biostimulant extracted from various plant pollen by green environmental protection process. It contains various water-soluble polysaccharide inside and outside the pollen cells, which are easily soluble in hot water and insoluble in ethanol, acetone and other organic solvents. Its main components are water-soluble sugars such as polysaccharides, oligosaccharides and monosaccharides. In addition, it is rich in amino acids, minerals and trace elements. Four polysaccharide components were obtained by macroporous resin chromatography and propylene dextran gel chromatography on the crude extract of SF pollen polysaccharide. Their average molecular weights are 24774.22 Da, 10718.15 Da, 66911.38 Da and 10328.089 Da respectively. Then, chemical method, chromatography-mass spectrometry and infrared spectroscopy were used to identify the structure of the polysaccharide components. From the perspective of structure, the functional application of SF pollen polysaccharide in anti-oxidation, promoting crop growth and inducing crop stress resistance was studied in depth.
2.2 Mechanism of Action of SF Pollen Polysaccharide
Plant polysaccharide is a kind of biological macromolecule widely existing in plants. It is a natural high molecular polymer made of aldose or ketose linked by glycosidic bonds. It is one of the basic substances to maintain the normal operation of life activities. According to the sources of polysaccharides, plant polysaccharides can be divided into plant flower&fruit polysaccharides, plant stem&leaf polysaccharides and plant rhizome polysaccharides. Among them, corn whisker polysaccharides, jujube polysaccharides, tea polysaccharides, aloe polysaccharides, konjac polysaccharides and ophiopogon japonicus polysaccharides have a wide range of biological activities. Their research is mainly concentrated in the field of medical and health care, with functions such as immune regulation, anti-tumor, hypoglycemic and liver protection [13]. However, the application in the field of agriculture is less, and most of them stay in the study of physiological activities of plant polysaccharides.
The main component of the Biostimulants SF Pollen Polysaccharide is the polysaccharide from the cell wall and its derivatives. As a signal molecule, it can widely participate in plant meristem division, cell growth, organ formation and other physiological activities, and also participate in plant disease defense and stress response. When external stimuli act on plants, they usually transfer signals into cells through a large number of Pattern Recognition Receptors (PRRS) on the cell membrane. The pattern related to plant-derived molecular recognition is called damage-associated molecular patterns(DAMP). In the process of pathogen invasion, the integrity of cell wall is often directly destroyed. Plants can perceive cell wall damage through DAMP and stimulate a series of signal responses to regulate the immune response of plants [14]. For example, the oligogalacturonic acid receptor kinase WAK, which adheres to the cell wall of plants, is one of the oligosaccharide activator receptors that have been studied in depth. At the same time, after recieving the SF pollen polysaccharide signal, plants will cause intracellular responses including changes of calcium ion currents in cytoplasm and cell nucleus, cytoplasmic acidification and reactive oxygen species generation. Ca2+ plays an important role in the regulation of cell functions, and acts as a second messenger to regulate physiological responses such as plant growth, development and stress resistance. The response of plants to the environment is often manifested at the cellular level as rapid change of calcium ion concentration, accompanied by the influx of extracellular calcium and the pumping of calcium from the intracellular calcium pool. Reactive oxygen species (ROS) are important signaling molecules in plants, which enable plants to respond to environmental stresses in time through gene expression and cellular metabolism.[14]. ROS burst is the sign of plant defense signals. When plants are infected by pathogens, ROS will be locally generated in large quantities to initiate defense system.(Fig. 4). The normal aerobic metabolism of plants is accompanied by the generation of a large number of superoxide anion free radicals and hydroxyl free radicals. Under normal conditions, superoxide dismutase and peroxidase in plants can scavenge free radicals. However, if plants are under stress conditions, excessive reactive oxygen species (ROS) cause protein and DNA damage, trigger the peroxidation of unsaturated fatty acids, resulting in generation of malondialdehyde (MDA), which will inactivated proteins, nucleic acids and others because of their cross-link. In vitro tests have proved that SF Pollen Polysaccharide has antioxidant ability which can scavenge excess free radicals in plants caused by environmental stress and biotic stress, and avoid the adverse physiological effects caused by ROS oxidative stress. (Fig. 5).
Brown pointed out [6] that non-lethal stress can lead to crop yield loss by converting assimilation into stress response metabolism, and the role of biostimulant is to reduce the response of plants to stress and redistribute the distribution of biomass in plants to achieve the purpose of yield increase (Fig. 1). Transcriptome and metabolome analysis of the plants applied with SF Pollen Polysaccharide showed that, compared with the CK, the genes involved in regulating the synthesis of flavonoids, glutathione and phenylpropanes in the wheat of the treatment group were differentially expressed, which were known to be important secondary metabolites involved in plant growth and development and stress resistance (Fig. 6). Therefore, SF Pollen Polysaccharide is a typical botanical source Biostimulant, which has the functions of promoting crop growth and improving crop abiotic stress resistance.
3 – Function and Application of SF Pollen Polysaccharide
3.1 Improve the ability of crops to resist abiotic stress (low temperature, drought, high temperature, etc.) and make crops grow healthier
SF Pollen Polysaccharide has a significant antioxidant effect, which can rapidly reduce the excessive accumulation of ROS oxygen free radicals in plants under stress conditions, playing a role in protecting cell membranes and reducing the accumulation of malondialdehyde.
Cowpea seedlings were sprayed with SF Pollen Polysaccharide and cultured under low temperature of 4 degrees for 2 days, and then placed under room temperature for 24 hours. The leaves of the cowpea seedlings with pollen polysaccharide treatment returned to be normal and erect, and the cold injury index was significantly lower than that of control (Fig. 7).
Soil acidification will seriously affect the root growth and nutrient absorption of crops. Under acidic soil conditions (pH 4.7), SF Pollen Polysaccharide can maintain normal growth of wheat roots, and the increase rate reached 21.66% (Fig. 8).
3.2 Significantly promote crop growth, improve photosynthetic efficiency, and make leaves turn green quickly
SF Pollen Polysaccharides enhances the absorption and transformation of nutrients in plants, and promotes the rapid growth of crops. SF Pollen Polysaccharide commonly shows positive effects on plant phenotypic indicators in 3 days after application and significant effects in 7 days after application.
Use SF Pollen Polysaccharide on pakchoi and wheat promoted the synthesis and accumulation of leaf chlorophyll, and increased the plant height of seedlings by 15% and 11% respectively compared with conventional fertilizers (Fig. 9).
Apply SF Pollen Polysaccharide 2 times during the growing period of Chinese lettuce, the yield increased by 6.2% (Fig. 10).
Apply SF Pollen Polysaccharide at the young fruit stage of dwarf tomatoes promoted fruit expansion, color improvement and maturity, and the single fruit weight increased by 64% compared with control, and the yield of first picking increased by 181% (Fig. 11).
3.3 Promote root growth, with more root hairs and longer root
SF-Pollen Polysaccharide significantly promotes plant root growth by regulating the metabolic pathways of flavonoids, glutathione and phenylpropane.
The results of the hydroponic experiment on wheat showed that the wheat seedlings cultured with SF-Pollen Polysaccharide had more and longer fibrous roots, and the roots had denser root hairs, which greatly increased the root surface area and good for the absorption of nutrients (Fig. 12).
SF-Pollen Polysaccharide also significantly promoted the root growth of dicotyledonous plants. The pumpkin and peanut seedlings with SF-Pollen Polysaccharide by soil application, the growth of main and lateral roots was proportional to the concentration of pollen polysaccharides (Fig. 13).
3.4 Significantly increase the seeds germination, help the seedling grow much stronger
SF Pollen Polysaccharide can be used for seed treatment of corn, wheat, soybean and other field crops. The recommended dosage is 1:50 between product and seeds. Seed treatment for corn with 0.1ppm SF Pollen Polysaccharide can significantly increase the seedling germination rate (7%), root length (40%), root weight (21%), leaf width (27%), stem diameter (16%) and fibrous root number (24%) (Fig. 14A). Seed treatment for wheat with 0.5 ppm SF Pollen Polysaccharide, the fresh weight of the seedling under the ground and above the ground increased by 32.5% and 14.77%, respectively (Fig. 14B). For soybean, the optimal dosage of SF Pollen Polysaccharide for seed dressing is 1ppm, the true leaf expansion rate of soybean increased by 18.2%, the root length increased by 23%, the root weight increased by 54.55%, and the plant weight increased by 10.4% (Fig. 14C).
3.5 Improve the quality of agricultural products, and with better taste
At the fruit enlargement stage of kiwifruit, apply SF Pollen Polysaccharide with foliar nutritional products such as calcium, magnesium and boron can significantly increase the content of Vitamin C and soluble sugar without affecting the single fruit weight of red-heart kiwifruit, and significantly improve the commercial value and nutritional value of kiwifruit (Fig. 15).
The application of SF Pollen Polysaccharide in the early ripening stage of cherry can promote early ripening, improve coloring and brightness of fruit peel, increase fruit firmness and single fruit weight, and increase the sugar content by 3 degrees compared with control (Fig. 16).
3.6 Improve soil micro-ecological environment and improve soil microbial diversity
SF Pollen Polysaccharide is a source of high-quality water-soluble organic matter, which can provide high-quality and rapidly absorbed organic matter for the soil and improve the soil micro-environment. The organic water-soluble fertilizer based on SF Pollen Polysaccharide from Chengdu Newsun, its content of organic matter is 200g/L, which not only supplement organic matter for soil and plants, but also improve soil hardening and salinization, soil structure, and soil microenvironment, and also promote soil microbial diversity (Fig. 17).
4 – Market Prospect Of SF Pollen Polysaccharide
According to the patent search, Pollen Polysaccharide has been granted two Chinese Invention Patents (ZL202010065033. X and ZL202010065021.7), and the IP right belongs to Chengdu Newsun Crop Science Co., Ltd. It is understood that the Patent application of “SF Pollen Polysaccharide Extract and Its Application in Plant Growth” (PCT / CN2020 / 139228) has been submitted in the United States and Brazil. As one of the few botanical source Biostimulants with independent intellectual property rights in the market, SF Pollen Polysaccharide has the characteristics of high activity, high safety and good compatibility. Through years of research and application, SF Pollen Polysaccharide series products have been successfully developed and can be used with common pesticides and fertilizers in the market (Fig. 18), significantly improving the fertilizer absorption and utilization rate. At the same time, the application method of SF Pollen Polysaccharide series products is flexible, which can match with various application methods such as flood irrigation, drip irrigation, foliar spraying, and agricultural aircraft spraying. It plays a role in increasing fertilizer absorption and utilization rate and enhancing crop stress resistance, and is widely used in many countries worldwide.
At present, the global market size of biostimulants is US $2.638 billion, and it is expected to reach US $5.04 billion by 2026. The compound annual growth rate from 2021 to 2026 is 11.71%, and the average marginal profit is 20-40%. The largest market share is in Europe, accounting for 37% of the total market size. With the rapid development of sustainable agriculture in China, the market potential of biostimulants has increased greatly. It is expected that China will become the fastest growing region in the global biostimulants market in 2025. As a new type of botanical source biostimulants, SF Pollen Polysaccharide has multiple functions, such as significantly improving the crops’ ability to resist the abiotic stress, increasing photosynthetic efficiency, promoting root growth, improving fertilizer absorption and utilization, and improving quality of agricultural products. In the future, SF Pollen Polysaccharide will become one of the core technologies in the global biostimulant market, providing a strong technical support for the sustainable development of global agriculture and global food security.
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