The Novel Biostimulant SF-Pollen Polysaccharide Promotes Plant Growth and Root Growth, With High Activities and Wide Application

Date:03-11-2023

1. Origin and definition of biostimulants

Over the past few decades, fertilizers and pesticides have played a vital role in agricultural production. With the increasing importance of the relationship between agriculture and environment, many countries and regions advocate the development of organic agriculture, which can obtain huge environmental and economic benefits on the one hand, and bring more health to consumers and farmers on the other hand (Casagrande M，Peigne J，Payet V，et al Organic farmers’ motivations and challenges for adopting conservation agriculture in Europe[J]. Organic Agriculture，2016，6(4):281-295.). Therefore, as an environmentally friendly, safe and efficient new green agricultural input, biostimulants have gradually entered the field of agricultural research and commercialization professionals, and have become a hot product in the agricultural input market, which is highly sought after by growers.

Biostimulants were first proposed by the Spanish mining company named Glesimme in 1974. In 1997, Zhang and Schmidt of Virginia Tech and State University redefined biostimulants: trace materials that promote plant growth. In the decades that followed, researchers conducted in-depth research on biostimulants, expanding their depth and outreach, finally the clear definition of plant biostimulants was made by the European Biostimulants Industry Council (EBIC) in 2012: biostimulants include substances and/or microorganisms that, when applied to plants or rhizospheres, its function is to stimulate natural processes to promote nutrient absorption, enhance nutrient conversion efficiency, and increase abiotic tolerance and crop yield.

 

2. Management of biostimulants

As a synergist different from fertilizer and pesticide, biostimulants have very different regulatory requirements and regulatory processes in different countries. Taking seaweed extract as an example, the product is registered as a plant growth regulator in Belgium and is authorized in accordance with the EU pesticide regulations. In France, seaweed extracts are registered as fertilizer products. In other UN member countries, such as the Netherlands and Spain, such products do not require registration and only require a simple notification to be submitted to the authority prior to launching to market.

In 2019, the European Union promulgated the world's first law (EU) 2019/1009 that classifies plant biostimulants separately as agricultural inputs, which firstly expanded the definition of fertilizers at the EU level, adding new fertilizer categories besides mineral fertilizers. And the plant biostimulant is listed as the sixth fertilizer category. At the same time, the new regulations also give the definition of biostimulants: "plant biostimulants are the products that do not depend on plant nutrients, can stimulate the natural processes of plants, thereby promoting the absorption of plant nutrients, improving the nutrient use efficiency of plants or plant rhizosphere, improving the ability of plants to resist abiotic stress, improving crop quality, and promoting the effective absorption of nutrients in soil or rhizosphere." Since July 16th, 2022, the regulation has been fully implemented, and since then plant biostimulants in Europe have become a separate agricultural input in fertilizer categories, instead of being regulated as pesticides.

There are currently no specific regulations in the United States for biostimulants, but in March 2019, the EPA issued a label guidance document for plant growth regulators and biostimulants, in which some products are excluded from the jurisdiction of plant growth regulators, including plant nutrients (fertilizer products), plant inoculants, soil amendments and vitamin-plant hormone products, which do not require pesticide registration. Although this draft guideline is not a regulatory document and has no legal effect, it can still foresee the future management trend and application value of biostimulants in the United States. (Chen Xiaolan,TU Xiayi. Recent progress in the management of biostimulants in Europe and the United States [J]. World Pesticides, 2020, 2, 42(2): 29-32.)

In China, the development of biostimulants began around 2010. During this period, although many small companies were involved in production and sales of biostimulant products. But due to their slow scientific research, the mechanism of actions and the active ingredients of these biostimulant products are unknown, China government cannot give a clear 'identity card' to these products. Therefore, there are many problems in product registration and production supervision, and such products have not been objectively and comprehensively understood by the market.

 

3. Classification of biostimulants

There is no uniform classification standard for biostimulants internationally, and they can be single compound, such as betaine and phosphates, or mixtures with complex compositions, such as seaweed extracts, beneficial microorganisms, and etc. Different scholars concluded that biostimulants include fulvic acid, humic acid, protein hydrolysates and other nitrogenous compounds, seaweed extract and its active ingredients, chitin, chitosan and derivatives, microbial agents, inorganic compounds, beneficial elements and plant extracts.

Recently, some researchers found that a Chinese company focusing on biotechnology research and development has developed a plant source biostimulant product - SF Pollen Polysaccharide. Compared with traditional biostimulants such as amino acids and humic acid in the market, SF Pollen Polysaccharide has the characteristics of natural source, safe and high bio-activities. It is understood that a lot of basic researches have been done on pollen polysaccharide, such as clarified the imfuence of pollen polisaccharide on crop growth and the regulatory pathways for growth promotion, identification of component structures of different molecular weights in pollen polysaccharide, and etc. At the same time, pollen polysaccharide has been applied to agricultural production and got significant achievements on enhancing crop stress tolerance, promoting plant root growth, increasing leaf photosynthetic efficiency and reducing chemical fertilizer use and increasing fertilizer efficiency.

 

4. Know about Pollen Polysaccharide

1) Source of Pollen Polysaccharide

Pollen, the flower sperm, is characterized by low fat and high protein, and contains fat, protein, various trace elements, amino acids and other nutrients necessary for human. Because of its large number of beneficial components, it is also known as plant source of ″complete nutrition″, becoming the important plant source that is researched and developed by health care and pharmaceutical industry.

Pollen polysaccharide is the plant-based biostimulant produced by Chengdu Newsun Crop Science Co., Ltd. (hereinafter referred to as "Chengdu Newsun") through the environmentally friendly extraction process. The crude extract of Pollen Polysaccharide is light brown powder, soluble in hot water, insoluble in ethanol, acetone and other organic solvents. Its main components are polysaccharides, oligosaccharides, monosaccharides and other water-soluble sugars. In addition, it has rich amino acids, minerals, trace elements, and etc.

2) Production process of Pollen Polysaccharide

Pollen polysaccharides are the soluble pollen extract that is extracted from pollen as raw material. The extraction process uses cellulase hydrolysis wall breaking technology and combines mechanical stirring, the rape pollen wall is broken under mild conditions, which can maximize the release of polysaccharides and other active ingredients in pollen and realize the efficient utilization of pollen resources.

 

Fig.1: Production process of Pollen Polysaccharide

 

3) Verification of Mechanism of actions and structure identification of pollen polysaccharide

The unclear mechanism of actions is one of the main reasons for the chaotic market and uneven effects of the biostimulants. Taking wheat and pumpkin as the research objects, Chengdu Newsun studied the main metabolic pathways of pollen polysaccharide regulation by metabolome and transcriptome linkage analysis, and found out that after pollen polysaccharide absorbed by plants, it regulates the expression of flavonoids, glutathione and phenylpropane related genes, enhancing glutathione metabolism and promoting flavonoid and phenylpropane biosynthesis to significantly promote the growth of crop roots. In addition, pollen polysaccharide also supplies plants with rich amino acids, trace elements and other nutrients, promotes chlorophyll synthesis, and strengthens leaf photosynthesis.

 

Fig. 2 Transcriptome differential gene expression heat map

At the same time, four polysaccharide components were obtained by macroporous resin column chromatography and acrylic glucan gel column chromatography of the pollen polysaccharides crude extract, of which the average molecular weights are 24774.22 Da, 10718.15 Da, 66911.38 Da and 10328.089 Da, respectively. The structures of polysaccharide components were identified by chemical method, chromatography-mass spectrometry and infrared spectroscopy, and the primary structures of pollen polysaccharide components were clarified.

The exploration of Chengdu Newsun in the mechanism of actions and structure identification of pollen polysaccharides breaks through the bottlenecks of unclear mechanism of actions, poor uniformity of raw materials and unclear composition of the existing biostimulants.

 

5. The uses of Pollen Polysaccharide

It is understood that pollen polysaccharide is the only plant-based biostimulant in the market till now, which is safer than other sources of biostimulants, more environmentally friendly in the production process, and has more functions.

1) Promote leaf growth

Pollen polysaccharide is plant-based polysaccharide, and its receptor proteins may participate in a variety of physiological activities of plants and regulate plant growth and development.

(1) Use pollen polysaccharide 2ppm to treat Chinese cabbage by foliar spray, it can increase leaf length, leaf width and stem fresh weight of Chinese cabbage by 11.18%, 30.14% and 16.81%.

Tab. 1 The results of Pollen Polysaccharide treatment on Chinese cabbage leaves

 

(2) In the field test, use pollen polysaccharide 0.3g/ha to treat Chinese lettuce by foliar spray. After 11 days of treatment, it had a significant effect on the plant height and stem thickness, increased by 15.2% and 5.7%. After 17 days of treatment, the leaf width increased by 21.2%, and theoretical yield increased by 6.2%.

 

Fig. 3: The results of Pollen Polysaccharide treatment on Chinese lettuce

(SF: Pollen Polysaccharide)

 

2) Increase crops’ resistance to stresses

After plants perceive pollen polysaccharide signals, they will cause intracellular reactions including changes in calcium ion flow in the cytoplasm and nucleus, cytoplasmic acidification, and reactive oxygen species production. Plants rapidly produce a large amount of reactive oxygen species under stress conditions, which can make plants respond to stresses in time by regulating gene expression and cell metabolism.

(1) Treat peas with pollen polysaccharide by foliar spray, then after 2 days, put the treated peas in the incubator with 4°C. 3 days later, put the cold treated peas under room temperature. The result showed pollen polysaccharide can significantly reduce the cold stress index of peas.

 

Tab. 2 The result of Pollen Polysaccharide treatment on peas under cold stress

 

Fig. 4: The result of Pollen Polysaccharide treatment on peas under cold stress

(2) Under low and high temperature conditions, the effects of pollen polysaccharide on the growth of soybean seedlings were tested. Compared with other biostimulants, pollen polysaccharides can significantly promote the increase of soybean root length, stem thickness and fresh weight under high and low temperature. Under high temperature condition, the soybean root length and fresh weight increased by 20.45% and 55.58%, respectively, which is significantly better than other biostimulants.

 

Fig. 5: The result of Pollen Polysaccharide treatment on soybean under heat stress

 

3) Seed treatment

Seed treatment is a very popular crop protection method in the world today, which brings great benefits to growers in terms of economy, health and control efficacy, so the development of seed treatment products has increased significantly. The active polysaccharides and other active ingredients in the plant-based biostimulant pollen polysaccharide have the effects of enhancing germination and promoting the growth of seedlings.

(1) For corn: under the culture condition of 14 °C-22 °C, use pollen polysaccharide 50 grams to blend 100kg corn seeds. After 27 days of treatment,compared with other seed treatment products, it was found that the corn plant with pollen polysaccharide treatment has stronger stem thickness, higher fresh root weight, more aerial roots and longer root length, and only the stem height was lower. And it’s obvious that there were no aerial roots for thoese treated with other product. So pollen polysaccharide for corn seed treatment can significantly increase the aerial root growth of corn and improve the lodging resistance of corn in late stage.

 

Fig. 6: The growth of corn seeds after Pollen Polysaccharide treatment

(2) For wheat: after seed soaking treatment, it was found that pollen polysaccharide had the promoting effect on plant height, root length, plant weight and root weight, and with pollen polysaccharide 2 ppm treatment, compared with the positive control, the plant height, root length, plant weight and root weight of wheat increased by 12%, 24%, 45% and 43%, respectively.

 

Fig. 7: The germination of wheats after Pollen Polysaccharide treatment

 

Fig. 8 The results of Pollen Polysaccharide on wheat roots and plant height

 

4) For plant nutritional products development

Pollen polysaccharide formulated with foliar fertilizers can improve crop stress resistance, increase nutrient absorption, and alleviate the problems of low foliar fertilizer efficiency or leaf burn.

(1) Compare the water-soluble fertilizers with and without pollen polysaccharide, after foliar spray, the water soluble fertilizer with pollen polysaccharide can significantly promote the accumulation of soluble solids in tomato and improve the quality of tomato fruits. The yield of tomato fruits was increased, and single fruit weight increased by 12.45%.

 

Tab. 3 The result of foliar fertilizer with pollen polysaccharide on the number of tomato fruits

Fig. 9: The result of water soluble fertilizer with pollen polysaccharide treatment on tomato

(2) For the greenhouse test, use the product with pollen polysaccharide by root drench with dose 7.5kg/ha, it can significantly improve the flavor of tomato fruits, increase the Vitamin C content by 20.3%, and increase the harvest rate by 4.9%.

 

Fig. 10: The result of pollen polysaccharide treatment on tomato

 

5) Increase fertilizer efficiency

(1) Pollen polysaccharide formulated with water soluble fertilizer to improve fertilizer efficiency and increase yield. The addition of 5-10kg/t pollen polysaccharides to water-soluble fertilizer can promote photosynthesis of Chinese cabbage, significantly increase the chlorophyll content by 10.97%, promote the growth of Chinese cabbage leaves, and increase the above ground biomass by 34.0%-41.78%. At the same time, the combination of water-soluble fertilizer with pollen polysaccharides can improve the nutritional quality of Chinese cabbage and promote the accumulation of Vitamin C content and soluble sugar content in leaves.

 

Fig. 11: The result of water soluble fertilizer with pollen polysaccharide treatment on Chinese cabbage

Fig. 12: The result of water soluble fertilizer with pollen polysaccharide treatment on the quality of Chinese cabbage

(2) According to the dose of compound fertilizer, reduce the dose of the compound fertilizer by 20%, and at the same time use different doses of pollen polysaccharide, that is, full dose of compound fertilizer (900kg/ha), reduced dose of compound fertilizer (720kg/ha), reduced dose of compound fertilizer with pollen polysaccharide 3, 5, 10kg/t. After tests, it was found that compared with the full dose of compound fertilizer treatment, the treatment of the reduced dose of compound fertilizer + pollen polysaccharide 10kg/t, the above-ground part fresh weight, root length, root weight, canopy width, leaf length and width of Chinese cabbage increased by 26.5%, 42.2%, 123.8%, 7.7%, 1.6% and 9.3%, respectively, and the promotion effect was obvious. Considering the input cost, the addition of pollen polysaccharides with the reduced dose of compound fertilizer can reduce the farmers’ cost and increase the fertilizer efficiency.

Tab. 4 The result of reduced dose of compound fertilizer with pollen polysaccharide treatment on Chinese cabbage

Fig. 13: The result of reduced dose of compound fertilizer with pollen polysaccharide treatment on Chinese cabbage

 

6) Improve soil eco-environment

(1) Formulate pollen polysaccharides with the soil conditioner for soil compaction, it can improve not onlythe structure of the compacted soil and the soil microbial environment, but also the adaptability of crops to the environment, and ensure the ecological balance between soil-microorganisms-plants.

 

Fig. 14: The result of pollen polysaccharide treatment on different soil microorganisms

 

(2) The treatment of Pollen polysaccharide with soil conditioner can alleviate soil salinization of cotton land in Xinjiang, and reduce the total soil alkalinity by 15%. After treated with pollen polysaccharide, the length and width of cotton leaves and chlorophyll content has significantly increased and the SPAD value of leaves has increased by 9.9%. Meanwhile, the number of cotton bolls was increased by 10.5%, and the cotton yield will also increase.

 

Fig. 15: The result of pollen polysaccharide treatment on cotton in the salinized soil

6. Industry outlook

As a new organic product, biostimulants have important application value for the development of organic and green agriculture. At present, the global biostimulants market is worth $2.638 billion and is expected to reach $5.04 billion by 2026, with a compound annual growth rate of 11.71% from 2021 to 2026, far exceeding other agricultural inputs, among which the Asia-Pacific region, China, India, Australia, etc. will become the main growth areas.

As a new type of plant-based biostimulant, pollen polysaccharide has the characteristics of green and safe production process, and friendliness to the environment, and is originated from plants and used on plants. It has the advantages of high activity, high safety and good compatibility, and can enhance crop resistance to low temperature, drought and high temperature, improve fertilizer utilization rate and crop yield and quality. It is of great value and significance to reduce the excessive dependence of crops on chemical fertilizers, improve the agricultural ecological environment, and reduce the impact of frequent global extreme climate on agricultural production.