Periodic Reporting for period 1 - SmartRoots (Smart roots for reducing greenhouse gases emissions from rice cropping)
Berichtszeitraum: 2023-01-15 bis 2025-01-14
Rice production is the main agricultural source of greenhouse gases (GHGs), including carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). The GHGs are produced and accumulated in rice paddies (flooded soils), and can be vented out to atmosphere via slow diffusion in the flooded soil, ebullition of large bubbles, or primarily via plant-mediated diffusion. The proportion of CH4 emitted via plant tissues accounts for up to 90% of total emissions from the rice cropping system. However, information on the plant characteristics influencing such GHGs emission is scarce.
The anatomical, physiological, and morphological characteristics that limit GHGs diffusion from rhizosphere to and along the roots, as well as the venting of these GHGs into the atmosphere, are largely unknown. The overarching objective of this project was to uncover the root characteristics that restrict GHG diffusion through rice roots. This objective was pursued by identifying traits of rice shoots and roots that can reduce both the venting of GHGs through plant tissues from soils to atmosphere and the production of GHGs in soils (oxidation of CH4 to CO2). It can be concluded that the shoots of rice do not present a major resistance to CH4 diffusion; instead, the roots are the primary sites that impede the diffusion of CH4 from the medium into the plants. Specific phenotypic variations in root characteristic exist among rice varieties and could potentially be exploited to develop high yielding cultivars with reduced GHG emissions.
The anatomical, physiological, and morphological characteristics that limit GHGs diffusion from rhizosphere to and along the roots, as well as the venting of these GHGs into the atmosphere, are largely unknown. The overarching objective of this project was to uncover the root characteristics that restrict GHG diffusion through rice roots. This objective was pursued by identifying traits of rice shoots and roots that can reduce both the venting of GHGs through plant tissues from soils to atmosphere and the production of GHGs in soils (oxidation of CH4 to CO2). It can be concluded that the shoots of rice do not present a major resistance to CH4 diffusion; instead, the roots are the primary sites that impede the diffusion of CH4 from the medium into the plants. Specific phenotypic variations in root characteristic exist among rice varieties and could potentially be exploited to develop high yielding cultivars with reduced GHG emissions.
During the development of this project, I used a multidisciplinary approach that combined state-of-the-art physiological measurements, including microsensing technology, gas trace laser analyzers, gas chromatography, mass spectrometry, microscopic characterization of plant tissues, and mathematical modelling. I evaluated different rice genotypes and grew them under various conditions to induce specific responses in root traits. Such responses include increased root porosity and roots with larger root diameters, which increase the area available for gas diffusion inside tissues; the development of root apoplastic barriers, thereby increasing resistances to gas diffusion; and the development of root systems with marked variations in adventitious or lateral roots, resulting in overall variations in resistances to gas diffusion. In addition to methodological developments for studying gas dynamics in plant tissues, the main outcome of this project was the finding that root traits are the primary resistant points restricting the diffusion of CH4 from the medium into the plants and, subsequently, to the atmosphere.
At this stage, the main results to emphasize are: i) the development of a method to measure diffusive resistances to O2 and respiratory O2 consumption in individual root cells, and ii) the identification of the glycerolesters at the suberized exodermis as compounds responsible for impeding gas diffusion through roots. Regarding the method, it will allow the research community to identify specific respiratory O2 consumption in the different root cell layers of plants, leading to a detailed understanding of root metabolism, energy production, and nutrient uptake. On the other hand, the finding that glycerolesters are key compounds responsible for reducing gas diffusion through roots represents a major advance in the field of plant apoplastic diffusion barriers and can serve as a basis for developing crops with specific traits that support high yield and low environmental impact.