N2 Applied (Norway)

The drying phenomenon in soils involves complex interactions between thermal, hydrological, and mechanical effects within a multiphase system. While several researches (both mechanics and mixture theory approach) has been applied to study various thermo-hydro-mechanical (THM) coupled processes in porous media, incorporating both multiphase flow and phase change in soil drying remains limited. This work addresses this research gap by deriving new governing equations for a two-phase flow model suitable for soil drying by extending the mixture coupling approach. The derived model is implemented in COMSOL Multiphysics and validated against experimental data, demonstrating good agreement between the model predictions and the ob- served results. A sensitivity analysis is performed to investigate the impact of critical parameters on the drying process. The findings reveal that volumetric strain is most sensitive to Young’s modulus, while the saturation of liquid water is most affected by intrinsic permeability. Additionally, preliminary results for a kaolinite clay sample during the drying process are presented, extending the applicability of the derived model to specific soil types. This research provides a comprehensive framework for fully THM coupled modelling of soil drying, which can serve as a basis for future investigations.

In this study, four tobacco transformants overexpressing the inorganic carbon transporter B gene (ictB) were screened for photosynthetic performance relative to the wild type (WT) in field-based conditions. The WT and transgenic tobacco plants were evaluated for photosynthetic performance to determine the maximum rate of carboxylation (Vc, max), maximum rate of electron transport (Jmax), the photosynthetic compensation point (Γ*), quantum yield of PSII (ΦPSII), and mesophyll conductance (gm). Additionally, all plants were harvested to compare differences in above-ground biomass. Overall, transformants did not perform better than the WT on photosynthesis-, biomass-, and leaf composition-related traits. This is in contrast to previous studies that have suggested significant increases in photosynthesis and yield with the overexpression of ictB, although not widely evaluated under field conditions. These findings suggest that the benefit of ictB is not universal and may only be seen under certain growth conditions. While there is certainly still potential benefit to utilizing ictB in the future, further effort must be concentrated on understanding the underlying function of the gene and in which environmental conditions it offers the greatest benefit to crop performance. As it stands at present, it is possible that ictB overexpression may be largely favorable in controlled environments, such as greenhouses.