Dr. David Guez – PhD Neurobiology – Ecotoxicology
Jim Wilson – Director – Founder – Visionary

Legumes, Bacteria and Hydrogen Uptake

It is well known in agricultural circles that crop rotation with legumes brings benefit to the subsequent crop. For a long time, these benefits have been attributed to the capacity of legumes to fix atmospheric nitrogen and thus enrich the soil in this essential element for plant growth. However, this restrictive view has been challenged in recent years. To understand why we need to know how legumes extract nitrogen from the atmosphere.

Legumes can form commensal relationships with specific bacteria that live in the soil through the formation of root nodules colonised by these bacteria. These bacteria, such as species of Rhizobium or Bradyrhizobium, can fix atmospheric nitrogen using their nitrogenase enzymatic system and provide the resulting nitrate (NH3) to the plant in exchange for carbohydrates. An obligate by-product of nitrogenase fixation of atmospheric nitrogen is hydrogen gas (H2). Some commensal bacteria can oxidise Hydrogen to produce water and ATP using endogen hydrogenase. The ones that can oxidise Hydrogen are called Hup+ (Hydrogen uptake positive). In contrast, the others that are not able to are called Hup- (Hydrogen uptake negative). From an energetic point of view, Hup+ commensals are more energetically efficient since they produce ATP and thus should provide more benefit to the plant in terms of cost benefits. If that was the case, Hup+ commensal should be favoured by legumes, and Hup- commensal should be the exception.

Unsurprisingly, this has been the admitted wisdom for some time. However, in a survey of the commensal association of wild legume in Nova Scotia, Annan et al. (2012) ¹ found that out of the 18 species sampled, only two possessed Hup+ nodules, a remarkable minority. Moreover, many if not most of the rhizobium-legume symbioses found in nature, especially those used in agriculture, are Hup-. These plants release H2 into the surrounding rhizosphere. Surprisingly, this Hydrogen is not lost to the atmosphere and disappears within 4 cm of the nodules.

The Benefits of Hydrogen in the Soil

Dong and Layzell (2001)² demonstrated that after 8-days of H2 treatment, soils started to consume H2, and resulted in a fivefold increase in soil O2 consumption and a net fixation of atmospheric CO2. In other words, H2 treatment of the soil resulted in an enrichment of the soil through the development of aerobic microorganisms. Soil enriched with Hydrogen proved to be beneficial to plant growth.

Maimaiti et al. (2007)³ isolated the bacteria responsible for H2 uptake with plant growth-promoting properties in both H2 treated soil and soil adjacent to Hup- nodules. The isolated bacteria were Variovorax paradoxus (formerly Alcaligenes). Most importantly, the isolate by themselves could significantly increase the primary root length of spring seedlings by 57-254% and increase plant growth by 11-27%. Surprisingly the benefit of Hydrogen exposure to plants is not all mediated by the growth of beneficial bacteria but also directly at the cellular level by scavenging Reactive oxygen species such as the hydroxy radical.

Environmental Stress and Reactive Oxygen Species

Research shows that abiotic stress in plants results in increased oxidative stress. For example, it can stunt growth resulting from mercury exposure (Cui et al., 2014)⁴, cadmium exposure (Cui et al., 2013)⁵, or aluminium exposure (Chen et al., 2014)⁶ is due to increased oxidative stress. The use of hydrogen-rich water alleviated the stunted growth in alfalfa exposed to mercury, cadmium or aluminium. The same is true for the Chinese cabbage exposed to cadmium⁷. In all cases, it also translated into a decrease in the bioaccumulation of these metals in the plant.

Salt stress, excessive UV exposure, or drought also translate into increased plant oxidative stress, thus detrimental to plant growth. And once again, the use of hydrogen-rich water alleviates the detrimental consequences on plant growth and germination (Xu et al., 2013; Xie et al. 2012, 2015; Yang et al. 2020; Fu et al., 2020)^8–12.

Hydrogen in the Field

Gaseous treatment of soil in the field, although impractical, has shown an increase of wheat yield in Australia of 10 to 31%, 18% on average (CSIRO Project CSP00050, 2007), and up to 16% for barley in Canada (Dong et al., 2003)¹³. However, it is now possible to provide Hydrogen and Oxygen-rich water using nanobubble infusion devices plugged in the existing irrigation infrastructure coupled to an on-demand Oxy-Hydrogen generator, such as those developed by Hydrogen Technologies here in Australia.

Why Oxy-Hydrogen and not just Hydrogen

The benefits of well-oxygenated soils are already well known. First, soil microorganisms that favour plant growth are aerobic, invertebrates that help avoid soil compaction, such as earthworms, need oxygen, and it is also the same for plant roots. In fact, oxygen-rich water promotes root growth. Second, the more oxygen in the soil, the less anaerobic process are likely such as denitrification. Denitrification is a process that impoverishes the soil and thus rob the grower of the needed benefits of nitrate on plant growth.

Moreover, Hydrogen promotes the development of aerobic bacteria with plant growth-promoting quality similar to legumes rotation. Of which one documented benefit is enabling access to much-needed phosphorus by the crop. Hydrogen supplementation also helps crops overcome abiotic stress allowing them to be productive with a yield increase of between 10 and 31%. Thus providing both gasses will improve soil and crop life synergistically.

The word “hydroxygen” is derived from the gaseous form of water, H2O. Two parts Hydrogen, one part oxygen (66.66% hydrogen – 33.33% oxygen of atomic count). Water becomes the delivery medium whereby the biologically available gasses of hydrogen and oxygen can be delivered to an environment where an organism benefits. When these gasses are infused into the water at nano scale, they defy buoyancy and suspend in the medium. This then allows deep penetration of the soil as the moisture is absorbed which ultimately changes the environment within that soil to favour aerobic life in all its biodiversity and benefit. This changes the game and a new world beckons; for all manner of species, in all manner of applications.

Contact Us / Work with Us

The Hydrogen Technologies on demand oxy-hydrogen generator coupled with our world-leading nanobubble infuser can plug into any existing irrigation system enabling an evolutionary advancement in Agriculture for all of us. We are keen to engage with both industry partners as well as collaborative research institutes and scientists to further the science and practical application and benefits of hydrogen and oxygen enriched irrigation waters around the world.

It is clear that these core biological understandings represent trillions of dollars of potential to increase food production around the world, to improve, regenerate and recultivate damaged soils and farmlands the world over, and to also sequester carbon from the atmosphere on what will be a massive scale and a globally significant advancement.

Please contact us and start a conversation towards a highly productive collaboration and sustainable shift without side effect or detriment. Just how nature intended, clean, natural, and beneficial for all.

References

1. Annan, H., Golding, A.-L., Zhao, Y. & Dong, Z. Choice of hydrogen uptake (Hup) status in legume-rhizobia symbioses. Ecol Evol 2, 2285–2290 (2012).
2. Dong, Z. & Layzell, D. B. H2 oxidation, O2 uptake and CO2 fixation in hydrogen treated soils. Plant Soil 229, 1–12 (2001).
3. Maimaiti, J. et al. Isolation and characterization of hydrogen‐oxidizing bacteria induced following exposure of soil to hydrogen gas and their impact on plant growth. Environ Microbiol 9, 435–444 (2007).
4. Cui, W. et al. Hydrogen-rich water confers plant tolerance to mercury toxicity in alfalfa seedlings. Ecotox Environ Safe 105, 103–111 (2014).
5. Cui, W., Gao, C., Fang, P., Lin, G. & Shen, W. Alleviation of cadmium toxicity in Medicago sativa by hydrogen-rich water. J Hazard Mater 260, 715–724 (2013).
6. Chen, M. et al. Hydrogen-rich water alleviates aluminum-induced inhibition of root elongation in alfalfa via decreasing nitric oxide production. J Hazard Mater 267, 40–47 (2014).
7. Wu, Q., Su, N., Cai, J., Shen, Z. & Cui, J. Hydrogen-rich water enhances cadmium tolerance in Chinese cabbage by reducing cadmium uptake and increasing antioxidant capacities. J Plant Physiol 175, 174–182 (2015).
8. Xie, Y., Mao, Y., Lai, D., Zhang, W. & Shen, W. H2 Enhances Arabidopsis Salt Tolerance by Manipulating ZAT10/12-Mediated Antioxidant Defence and Controlling Sodium Exclusion. Plos One 7, e49800 (2012).
9. Xie, Y. et al. Hydrogen-rich water-alleviated ultraviolet-B-triggered oxidative damage is partially associated with the manipulation of the metabolism of (iso)flavonoids and antioxidant defence in Medicago sativa. Funct Plant Biol 42, 1141–1157 (2015).
10. Xu, S. et al. Hydrogen-rich water alleviates salt stress in rice during seed germination. Plant Soil 370, 47–57 (2013).
11. Fu, X. et al. Hydrogen rich water (HRW) induces plant growth and physiological attributes in fragrant rice varieties under salt stress. (2020) doi:10.21203/rs.3.rs-21074/v1.
12. Yang, L., Tian, J., Zhu, M., Yu, B. & Sun, Y. Hydrogen-Rich Water Improvement of Root Growth in Maize Exposed to Saline Stress. (2020) doi:10.21203/rs.3.rs-101510/v1.
13. DONG, Z., WU, L., KETTLEWELL, B., CALDWELL, C. D. & LAYZELL, D. B. Hydrogen fertilization of soils – is this a benefit of legumes in rotation? Plant Cell Environ 26, 1875–1879 (2003).