Ascophyllum nodosum: The Super Seaweed Boosting Plant Growth

Delve into the North Atlantic's coastal waters, where the brown seaweed Ascophyllum nodosum has thrived for millennia. Long before synthetic fertilizers and modern agricultural practices, coastal farmers recognized the inherent power of this resilient seaweed. For centuries, it was harvested and incorporated into the soil, enriching fields and boosting crop yields through its wealth of organic matter and essential nutrients. Today, scientists have unlocked the secrets behind this seaweed's biostimulant properties, revealing its potential to transform sustainable agriculture.

What Makes Ascophyllum nodosum Special?

Ascophyllum nodosum is a large, perennial alga easily recognizable by its long, leathery fronds and distinctive air-filled vesicles (bladders) that aid in buoyancy and light absorption.The unique habitat has forged the seaweed's resilience and contributed to its extraordinary composition: 

Polysaccharides

• Alginates: These complex carbohydrates contribute to the seaweed's structure and water-holding capacity. They also play a role in improving soil structure and nutrient retention.
• Fucoidans: These sulfated polysaccharides are known for their anti-inflammatory, antiviral, and antioxidant properties. They can also stimulate plant immune responses and enhance stress tolerance.
• Laminarin: This storage carbohydrate provides energy for the seaweed and can stimulate plant growth and defense mechanisms.

Phytohormones

• Cytokinins: These hormones promote cell division and growth, delay senescence, and enhance nutrient uptake.
• Auxins: These hormones regulate various aspects of plant growth and development, including root formation, cell elongation, and flowering.
• Betaines: These osmoprotectants help plants cope with abiotic stresses like drought and salinity.

Phenolic Compounds

• Phlorotannins: These polyphenols have strong antioxidant and anti-inflammatory properties, protecting plants from oxidative damage caused by environmental stressors.

Other Bioactive Compounds

• Amino Acids: Building blocks for proteins, essential for plant growth and development.
• Vitamins: Contribute to various metabolic processes in plants.
• Minerals: The main mineral are Na, Mg, K, Cl and SO₄, provide essential nutrients for plant growth and function.

The unique combination of these bioactive compounds in Ascophyllum nodosum extract (ANE) creates a synergistic effect. Synergy, in this context, refers to the phenomenon where the combined action of multiple compounds is greater than the sum of their individual effects. In simpler terms, each compound within the extract contributes to the overall efficacy, and their combined influence on plant physiological processes is significantly more pronounced than if applied independently. This phenomenon can be attributed to the complex interactions between the various compounds and their influence on multiple plant signaling pathways.

Benefits for Your Crops

Ascophyllum nodosum extract (ANE), applied to soil, hydroponic systems, or directly onto leaves as foliar sprays, deliver a wide array of benefits:

Enhanced Growth and Yield

Better nutrient uptake, improved photosynthesis, and increased stress tolerance lead to stronger plants, higher yields, and fruits/vegetables rich in nutrients.

Boosted Crop Quality

• Elevated Nutrient Content: Improved nutrient uptake and utilization by plants lead to higher levels of essential vitamins, minerals, and antioxidants in fruits and vegetables.
• Extended Shelf Life: Seaweed extracts can influence the expression of genes involved in fruit ripening and senescence. This can delay the ripening process and extend the shelf life of harvested produce.

Healthier Soil Environment

• Enhanced Soil Structure: Alginates improve soil aggregation and stability, leading to better aeration and water drainage. This creates a more favorable environment for beneficial soil microbes that contribute to plant health.
• Improved Water Retention: Alginates' hygroscopic properties enhance the soil's ability to retain water, reducing the risk of drought stress for plants.
• Increased Nutrient Availability: Improved soil structure and microbial activity promote the breakdown of organic matter and the release of essential plant nutrients into the soil solution.

Disease Suppression

• Promotion of Beneficial Microbes: Seaweed extracts can stimulate the growth and activity of beneficial soil microorganisms like bacteria and fungi that act as antagonists against plant pathogens. This helps suppress soilborne diseases naturally.
• Direct Antipathogenic Effects: Some seaweed extract components, such as phlorotannins, have been shown to exhibit direct antifungal and antibacterial properties, further contributing to disease resistance in plants.

Studies have shown that A. nodosum extract influences plant growth by regulating molecular, physiological, and biochemical processes, as well as interacting with hormone production and signaling pathways. This complex interaction contributes to its observed biostimulant effects.

Scientifically Proven Efficacy

Ascophyllum nodosum extract (ANE) effectiveness is supported by a wealth of scientific research and field trials, demonstrating its significant impact on various crops.

A.nodosum Extract Improves (ANE) Fruit Quality, Growth and Yield of Crops 

Numerous peer-reviewed studies published in reputable scientific journals have validated ANE's efficacy. A meta-analysis of 20 studies, published in Agriculture, Ecosystems & Environment, concluded that ANE consistently improves crop yield by an average of 10-20% across various crops.

Improved Fruit Quality: ANE application has been shown to enhance fruit quality in several crops, including:

• Watermelon: A field trial conducted by the University of Florida reported a 12% increase in brix levels (sugar content) in watermelons treated with ANE (Abdel-Mawgoud et al., 2010).
• Apple: Research found that ANE-treated apple trees exhibited a 20% increase in fruit firmness and a 15% reduction in storage losses  (Basak, 2008) .
• Grape: A study revealed that ANE-treated grapevines produced wines with a 10% higher concentration of phenolic compounds, contributing to improved flavor and aroma (Frioni et al., 2018).
• Olive: A field study conducted in Spain demonstrated that ANE application increased olive oil yield by 8% and improved oil quality by enhancing polyphenol content (Chouliaras et al., 2009)  .

Enhanced Nutrient Uptake: ANE facilitates better absorption of essential nutrients, resulting in:

• Grape: Researches reported a 15%  increase in nitrogen uptake and a 20% increase in potassium uptake in grapevines treated with ANE (Norrie et al., 2002; Sabir et al., 2014; Frioni et al., 2018).
• Tomato: A study found that ANE application increased calcium uptake in tomato plants by 18%, resulting in reduced blossom end rot incidence (Di Stasio et al., 2018).
• Canola: A field trial in Canada demonstrated that ANE treatment increased nitrogen uptake in canola by 12%, leading to a 10% yield increase (Jannin et al., 2013).

Growth Promotion in Leafy Vegetables: ANE treatment has proven effective in boosting growth, yield, and nutrient content in leafy greens like spinach and lettuce. A study published in Plant Physiology and Biochemistry found that watering with 1g/L ANE before harvest improves spinach yield by 15% and enhanced vitamin C content by 20% (Fan et al., 2014).

ANE Improves Plant Growth by Regulating Phytohormone Biosynthesis in Plants

Phytohormones (plant hormones) are low molecular weight compounds, present in very small amounts to regulate a number of physiological and developmental processes in plants. Research suggests that the growth-promoting effect of ANE is due to the presence of various "phytohormone-like" substances. ANE contains high concentration of indole acetic acid (IAA), known for promoting growth. It's particularly rich in cytokinins, hormones crucial for cell division and delaying plant aging. ANE also influences gibberellin production, further contributing to growth and development.

The unique blend of phytohormone-like substances in ANE, including auxin, cytokinin, gibberellic acid, work harmoniously to regulate plant processes. ANE not only supplies these hormones directly but also stimulates the plant's production of its own hormones. This dual action makes ANE a powerful natural tool for enhancing plant growth, increasing cell division, delaying senescence, and boosting overall plant health.

ANE Reduces Abiotic Stress in Plants 

Plants are constantly challenged by various environmental stresses that limit their growth and yield. For example, rice yields declined 15% per 1°C rise in mean growing season temperature, measured from 1979 to 2003 (Peng et al. 2004). Due to the complex metabolic pathways involved in stress tolerance, the creation of stress-tolerant crops through genetic engineering has achieved limited success. Another sustainable approach to improve stress tolerance in plants is to use extracts from A. nodosum (Table 3).

ANE Improves Plant Salt Tolerance

Soil salinity poses a significant threat to global agriculture, affecting over 800 million hectares of land and severely impacting crop productivity. Even mild salt stress induces physiological drought in plants, hindering growth by reducing water uptake and cell expansion. Prolonged exposure to high salinity disrupts ion homeostasis, leading to membrane damage, metabolic dysfunction, and ultimately cell death. A. nodosum extract (ANE) has demonstrated promising potential in enhancing plant salt tolerance across various crops:

• Tomato: ANE application has been shown to promote the accumulation of essential minerals, antioxidants, and amino acids in tomato plants grown under salt stress conditions (Kumar and Sahoo, 2011). This helps maintain cellular functions and mitigate the detrimental effects of salinity.
• Passion Fruit: ANE treatment has been reported to improve passion fruit growth and yield under salt stress by enhancing nutrient uptake and reducing oxidative damage (Xu and Leskovar, 2015).
• Avocado: ANE application has been found to mitigate the negative impacts of salt stress on avocado growth and yield by improving nutrient uptake and water-use efficiency (Shukla et al., 2018).

Mechanisms of Salt Stress Mitigation by ANE:

ANE's diverse bioactive components contribute to salt stress tolerance through various mechanisms:

• Osmotic Adjustment: ANE helps plants maintain cellular water balance by acting as an osmoprotectant, protecting cells from dehydration and facilitating water uptake.
• Ion Regulation: ANE aids in regulating ion uptake and compartmentalization, preventing the toxic accumulation of ions within plant cells.
• Antioxidant Activity: ANE's antioxidant properties help scavenge reactive oxygen species (ROS) generated under salt stress, protecting cellular structures and maintaining metabolic processes.
• Gene Expression Modulation: ANE has been shown to induce the expression of stress-protective genes, such as those encoding Late Embryogenesis Abundant (LEA) proteins, which help stabilize cellular structures and proteins under stress conditions (Goñi et al., 2016).

ANE Reduces Drought Stress in Plants

Drought, a widespread and persistent environmental stressor, poses a significant threat to global crop production. Both physical (lack of water) and physiological (impaired water uptake) drought negatively impact plant physiology, leading to reduced nutrient availability, impaired photosynthesis, and ultimately, decreased crop yields. It is estimated that drought affects nearly 50% of agricultural land worldwide.

Ascophyllum nodosum extract (ANE) has emerged as a promising tool for mitigating drought stress in various crops:

• Broad-Spectrum Protection: ANE has demonstrated efficacy in reducing drought damage across diverse crops, including beans, tomatoes, oranges, and spinach (Nabati et al., 2019).
• Multi-Level Mitigation: ANE's bioactive compounds, although not yet fully characterized, have been shown to alleviate drought stress through a multifaceted approach, modulating molecular, cellular, and physiological responses in plants.
• Gene Expression Regulation: ANE treatment has been found to upregulate the expression of genes involved in stress tolerance, including those related to osmoprotectant synthesis, antioxidant production, and stomatal regulation (Goñi et al., 2016).
• Osmolyte Accumulation: ANE stimulates the accumulation of osmolytes, such as proline and soluble sugars, which help maintain cell turgor and protect cellular structures under drought conditions (Shukla et al., 2018).
• Enhanced Antioxidant System: ANE boosts the production of antioxidant enzymes, such as superoxide dismutase and catalase, which scavenge harmful reactive oxygen species (ROS) generated during drought stress (Kumar and Sahoo, 2011).
• Improved Gas Exchange: ANE helps regulate stomatal opening and closure, optimizing gas exchange for photosynthesis while minimizing water loss through transpiration (Rayirath et al., 2008).

ANE Enhances Plant Defense Response Against Pathogens

Climate change and intensive agricultural practices have led to a rise in crop diseases caused by bacteria, fungi, and viruses, threatening agricultural productivity. Ascophyllum nodosum extract (ANE) offers a natural and sustainable solution to enhance plant defense mechanisms.

ANE-Induced Disease Resistance:

Seaweeds like A. nodosum have evolved robust defense systems against their own pathogens, and these properties can be harnessed for crop protection. ANE's bioactive compounds have been shown to stimulate plant immune responses and activate defense mechanisms against a variety of pathogens.

• Cucumber: ANE treatment, combined with reduced fungicide use, enhanced resistance against Phytophthora melonis in cucumber seedlings by activating defense enzymes such as peroxidase, polyphenol oxidase, and others (Jayaraj et al., 2008). It also induced systemic resistance against Phytophthora capsici (Panjehkeh and Abk, 2014).
• Carrot: Foliar application of ANE significantly reduced disease progression caused by the fungi Alternaria radicina and Botrytis cinerea in carrots (Jayaraj et al., 2008).
• Other Crops: Studies have shown ANE's potential to reduce the development of various fungal pathogens in cucumbers (Alternaria cucumerinum, Didymella applanata, Fusarium oxysporum, Botrytis cinerea) by inducing defense genes and enzymes (Jayaraj et al., 2008).

Reduced Reliance on Chemical Fungicides:

The strategic use of ANE as part of an integrated disease management approach can lessen the reliance on chemical fungicides, offering a safer and more environmentally friendly method for controlling plant diseases.

ANE Improves Soil Health

Ascophyllum nodosum extract (ANE) not only acts as a biostimulant to enhance plant growth and development but also directly contributes to improving soil health through its unique composition.

Alginates for Enhanced Soil Structure and Nutrient Availability:

• Chelation: ANE contains alginates, natural polysaccharides that act as chelating agents. They bind to metal ions in the soil, forming complexes that increase the availability of essential micronutrients for plants (Jannin et al., 2013).
• Improved Soil Structure: Alginates create a gel-like matrix that improves soil structure by increasing water retention capacity and aeration, leading to a more favorable environment for root growth and microbial activity (Khan et al., 2009).

Prebiotic Effects and Enhanced Microbial Activity:

ANE acts as a prebiotic, stimulating the growth and activity of beneficial soil microorganisms. This has been shown to improve the growth of strawberries and carrots by increasing microbial diversity and enhancing nutrient cycling in the soil (Verkleij, 2015).

• Root Exudate Stimulation: ANE promotes the production of root exudates, such as flavonoids, which attract beneficial bacteria to the rhizosphere (Rayorath et al., 2008).
• Nodule Formation: ANE has been reported to induce rhizobium nodule formation in leguminous plants, facilitating nitrogen fixation and improving soil fertility (Khan et al., 2009).

Biocontrol Potential:

Components within ANE have shown potential as biocontrol agents against harmful organisms, including bacteria, viruses, fungi, and nematodes (Jayaraj et al., 2011). For example, alkaline hydrolyzed seaweed extract has been found to significantly reduce populations of root-knot nematodes (Meloidogyne javanica) (Halpern et al., 2008).

Summary

Numerous studies have demonstrated the efficacy of Ascophyllum nodosum extract in various crops, from fruits and vegetables to grains and ornamentals. The seaweed's unique blend of nutrients works synergistically to unlock the full potential of plants. Here is a table summarizing some of the benefits of Ascophyllum nodosum extract on plants that have been researched: