Tracing Mineral Blockages in Ginseng Red Skin Syndrome via Advanced Bioimaging

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Ginseng, known scientifically as Panax ginseng C.A. Meyer, has been a cornerstone of traditional medicine for over 3,000 years. Revered for its ability to combat fatigue, boost immunity, and promote longevity, this herb holds immense cultural and economic value.

However, cultivating ginseng is a challenging endeavor. The plant requires four to six years to mature, and during this time, it is vulnerable to a disorder called red skin syndrome. This condition manifests as reddish-brown lesions on the roots, severely impacting their quality and marketability.

For decades, researchers have debated the root cause of this syndrome, with theories ranging from mineral toxicity to microbial infections.

A groundbreaking study published in 2025 in the journal Industrial Crops & Products has shed new light on this issue, revealing that disruptions in mineral transport within the plant’s roots play a central role.

The Mystery of Red Skin Syndrome

Red skin syndrome has long perplexed farmers and scientists. The disorder is most prevalent in ginseng grown in acidic, albic soils—a type of soil characterized by low pH and high levels of aluminum and iron.

Albic soils are nutrient-poor, sandy soils often found in temperate regions, and their acidic nature (pH below 5.5) makes minerals like aluminum more soluble and toxic to plants. Affected roots develop cracked outer layers and rusty discoloration, often leading to secondary infections by fungi or bacteria.

Early research pointed to two possible causes. The first theory suggested that excessive aluminum and iron in the soil directly damaged the roots, while the second proposed that pathogens like Fusarium species exploited weakened tissues.

However, the 2025 study shifts the focus inward, examining how minerals are distributed within the root itself. Using advanced imaging technology, the researchers mapped the movement of 11 essential elements in healthy and diseased roots, uncovering a critical breakdown in nutrient transport mechanisms.

Their findings highlight the epidermis—the root’s outermost layer—as a key player in the development of red skin syndrome.

Soil Analysis and Its Role in Red Skin Syndrome

The study began with a thorough analysis of soil from a ginseng farm in Tonghua City, China, where red skin syndrome is common.

The soil was acidic, with a pH of 4.3, and contained high levels of exchangeable aluminum (1.7 mg/kg)—a form of aluminum that is readily available to plants and toxic in excess—and available iron (31.1 mg/kg), which refers to iron dissolved in soil water and accessible for plant uptake.

These conditions are typical of albic soils, which are notorious for promoting mineral toxicity in plants. Additionally, the soil showed deficiencies in key nutrients:

• potassium levels were critically low at 18.5 mg/kg,
• phosphorus was only moderately available at 12.1 mg/kg.

 Potassium is vital for enzyme activation and water regulation, while phosphorus is essential for energy transfer and DNA synthesis. Organic matter content, a crucial factor for soil health that improves nutrient retention and microbial activity, was also deficient at 5.9 g/kg.

These findings align with previous studies linking red skin syndrome to acidic, nutrient-poor soils. The imbalance in mineral availability creates a hostile environment for ginseng roots, forcing them to adopt defensive mechanisms that ultimately backfire.

Advanced Techniques for Mapping Mineral Distribution

To understand how minerals move within ginseng roots, the researchers employed two cutting-edge technologies:

• laser ablation-inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS)
•  inductively coupled plasma mass spectrometry (ICP-MS).

LA-ICP-TOF-MS is a sophisticated imaging tool that uses a laser to vaporize tiny sections of plant tissue, which are then ionized and analyzed by a mass spectrometer. This technique provides high-resolution maps of elemental distribution, showing exactly where minerals like aluminum or phosphorus accumulate.

ICP-MS, on the other hand, quantifies the concentration of these elements in digested tissue samples. By combining these approaches, the team could visualize both the location and quantity of minerals in healthy and diseased roots.

For example, they analyzed lateral roots—smaller side roots critical for nutrient uptake due to their large surface area—and compared their structures microscopically. Diseased roots showed clear physical damage, including cracked epidermis and gaps between layers, which likely disrupted nutrient transport.

Key Mineral Imbalances in Diseased Ginseng Roots

The study revealed dramatic differences in mineral distribution between healthy and red skin-affected roots. Aluminum and iron, two elements known for their toxicity in acidic soils, were found in much higher concentrations in the epidermis of diseased roots.

Aluminum levels in the epidermis of red skin roots were 2.3 times higher than in healthy roots, while iron concentrations were 1.7 times higher. These metals formed a dense barrier in the outermost layer, preventing their inward movement.

As a result, aluminum levels in the epidermis were 10 times higher than in the cortex (the middle layer of the root responsible for nutrient storage and transport) and 8 times higher than in the stele (the innermost layer containing vascular tissues that transport water and minerals to the rest of the plant).

This accumulation suggests that the plant traps toxic metals in the epidermis to protect its inner tissues—a survival strategy that inadvertently damages its own structure.

Calcium, magnesium, and manganese also showed abnormal patterns. In healthy roots, these elements were evenly distributed across all layers. However, in red skin roots, they clustered heavily in the epidermis.

• Calcium levels in the epidermis of diseased roots were 1.5 times higher than in healthy roots, while magnesium and manganese increased by 1.3 and 1.4 times, respectively.

The researchers speculate that excess calcium might harden cell walls, exacerbating the cracking and separation observed in the epidermis. Calcium is crucial for cell wall stability and signaling, but its overaccumulation can rigidify tissues, reducing flexibility.

Phosphorus and sulfur, essential for energy production and enzyme function, faced significant transport barriers. In healthy roots, phosphorus flowed freely to the stele, where concentrations reached 9.6 mg/g.

In red skin roots, however, phosphorus became trapped in the epidermis and cortex, reducing its concentration in the stele by 19.6%.

Sulfur followed a similar pattern, with stele concentrations dropping by 13.2%. This blockage starved the inner tissues of critical nutrients, impairing the plant’s overall health. Sulfur is a key component of amino acids and antioxidants, and its deficiency can weaken a plant’s defense against oxidative stress.

Micronutrients like zinc, copper, and boron were severely depleted in red skin roots. Zinc levels in the epidermis dropped by 55.7%, while copper decreased by 58.7%.  Zinc is vital for enzyme function and protein synthesis, and copper plays a role in photosynthesis and lignin formation.

Boron, which is critical for cell wall formation and membrane integrity, plummeted by over 90% across all tissues.

These deficiencies likely weakened the root’s structural integrity, making it more susceptible to physical damage and pathogens.

Potassium behaved uniquely. While its overall levels decreased in the epidermis and cortex of diseased roots, more potassium reached the stele—a 7.7% increase compared to healthy roots.

This suggests that the plant prioritizes potassium transport to maintain basic cellular functions, even as other nutrients falter. Potassium regulates stomatal openings, enzyme activation, and osmotic balance, making it indispensable for survival.

The Epidermis as a Mineral Barrier in Ginseng Roots

The study’s most significant conclusion is that the epidermis, while intended to protect the root, becomes a dysfunctional barrier in red skin syndrome. The epidermis is the outermost cell layer of the root, acting as the first line of defense against soil toxins and pathogens.

In healthy plants, it selectively absorbs water and nutrients while blocking harmful substances. However, in red skin ginseng, this layer cracks under the strain of accumulated minerals, losing its ability to regulate uptake.

Aluminum and iron bind to phosphorus and sulfur, forming insoluble compounds like aluminum phosphate (AlPO₄) that further block nutrient transport.

Over time, this leads to a vicious cycle: the epidermis cracks under the strain of accumulated minerals, impairing its ability to regulate what enters the root. Damaged tissues then become breeding grounds for opportunistic pathogens, compounding the problem.

This phenomenon mirrors strategies seen in other plants. For instance, cattails (Typha latifolia) trap lead and aluminum in their epidermis to prevent vascular damage, while vetiver grass (Chrysopogon zizanioides) localizes mercury in its outer layers.

However, ginseng’s slow growth and high susceptibility to soil conditions make it uniquely vulnerable. Once the epidermis is compromised, the plant struggles to recover, leading to irreversible damage.

Soil Management and Future Solutions

The study’s findings have immediate implications for ginseng farmers. Addressing soil acidity is a critical first step. Applying lime (calcium carbonate) to raise soil pH to 5.5–6.5 could reduce aluminum and iron solubility, minimizing their toxicity.

Balanced fertilization is equally important. Potassium-deficient soils require supplements to meet the recommended 200 mg/kg, while phosphorus levels can be improved with rock phosphate, a natural mineral fertilizer. Micronutrient deficiencies might be addressed through foliar sprays containing zinc, copper, and boron.

Long-term solutions could involve breeding ginseng varieties resistant to mineral stress. For example, plants with enhanced aluminum exclusion genes (genes that prevent aluminum uptake) or more efficient phosphorus transporters could bypass epidermal blockages.

Advanced imaging tools like LA-ICP-TOF-MS might also be adapted for field use, allowing farmers to detect mineral imbalances early and adjust their practices accordingly.

Revolutionizing Ginseng Farming Through Mineral Transport Insights

While this study answers many questions, it also opens new avenues for research. Future studies could explore the genetic mechanisms behind mineral transport, identifying genes that regulate how elements move through root tissues.

For instance, ion transporters—proteins that shuttle minerals across cell membranes—could be modified to enhance nutrient uptake efficiency. Additionally, the role of microbes in red skin syndrome warrants further investigation.

Although the study found no direct link between pathogens and mineral transport disruptions, cracked epidermis likely invites secondary infections. Understanding these interactions could lead to integrated pest management strategies that combine soil amendments with biocontrol agents.

Collaboration between farmers, agronomists, and geneticists will be essential. Field trials testing soil amendments and resistant cultivars over multiple growing seasons could provide practical insights.

Meanwhile, advancements in portable imaging technology could revolutionize how farmers monitor crop health, enabling real-time adjustments to fertilization and irrigation.

Conclusion

Red skin syndrome signals deep mineral imbalances in ginseng, rooted in soil chemistry and the plant’s own defenses. The 2025 study highlights how the epidermis, while protective, can trap toxins and block nutrients.

For farmers, simple steps like adjusting soil pH offer real solutions. For scientists, it opens new paths in studying mineral transport. With smarter cultivation, ginseng’s future as a valued medicinal crop is bright.