N-fertilizer synthesis for agriculture sustains about half of the human population. Recent studies show that nitrogen input from N-fertilizer synthesis and river runoff will pose a serious and growing problem with intensifying climate change. Excessive fertilization also leads to the release of considerable amounts of nitrous oxide into the atmosphere posing additional aggravating challenges to the bioenergy balance of modern society. To address these major societal challenges, improvements to today’s agricultural strategies are necessary. Here we aim to develop a new, non-invasive quantum sensing approach to directly observe metabolic transformation in the rhizosphere to acquire currently inaccessible knowledge.
We propose a quantum spin technology to image biochemical pathways in the rhizosphere with unprecedented chemical detail and sensitivity. Specifically, the proposed technology transfers the quantum entangled nuclear spin order of hydrogen gas, to metabolites, including nitrate, amino acids and pyruvate, to enable molecular imaging of their metabolic transformations without any penetration depth limitations such that molecular turnover and metabolism can be observed directly in soil. We will conduct proof-of-concept demonstrations of our quantum sensing approach to study nitrogen assimilation of barrel medic (Medicago truncatula). M. truncatula is a model legume for biological nitrogen fixation mediated by rhizobia and symbiosis with arbuscular mycorrhizal (AM) fungi which transport nutrients, including nitrate, to the plant. In return, rhizobia and AM fungi receive fixed carbon from the plant. However, there is no technology to date that can track individual metabolic events non-invasively in unperturbed soil to answer some of the most important questions about which metabolic pathways the molecules actually follow. After establishing this new quantum sensing approach to molecular imaging on roots, it can be applied to any plant of interest to study their molecular machinery.
Current technology designed to non-invasively monitor the metabolic turnover of naturally occurring biomolecules in plants, roots or smaller model systems faces major obstacles. In case of optical techniques, obstacles include optical penetration depth limitations and chemical specificity. In contrast to optical techniques, Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) are well-established non-invasive techniques that easily report on small changes in chemical structure and perform non-invasive imaging. However, NMR, and even more so MRI, are notoriously insensitive, require large samples and high concentrations, therefore the study of low-concentration metabolites remains out of reach. With quantum entangled sources of nuclear spin order, parahydrogen in particular, we overcome current technological shortcomings and achieve sensitivity gains of up to seven orders of magnitude, which promise tracking of low concentration metabolites and their chemical transformations deep inside soil.
With succesfull completion of our aims we will have established a new quantum technology for non-invasive imaging of nitrogen assimilation in the rhizosphere. This implies that the same technology can be used to understand many other metabolic pathways that are not easily accessible today. Ultimately, this technology will help produce crops that increase carbon uptake in soil, helping to remove CO2 from the atmosphere and decreasing nitrous oxide (N2O) emissions.
