The intersection of nitrogen nutrition and water use in plants: new paths toward improved crop productivity

Water and nitrogen availability limit crop productivity globally more than most other environmental factors. Plant availability of macronutrients such as nitrate is, to a large extent, regulated by the amount of water available in the soil, and, during drought episodes, crops can become simultaneously water and nitrogen limited. In this review, we explore the intricate relationship between water and nitrogen transport in plants, from transpiration-driven mass flow in the soil to uptake by roots via membrane transporters and channels and transport to aerial organs. We discuss the roles of root architecture and of suberized hydrophobic root barriers governing apoplastic water and nitrogen movement into the vascular system. We also highlight the need to identify the signalling cascades regulating water and nitrogen transport, as well as the need for targeted physiological analyses of plant traits influencing water and nitrogen uptake. We further advocate for incorporation of new phenotyping technologies, breeding strategies, and agronomic practices to improve crop yield in water- and nitrogen-limited production systems

Optimal surrogate modelling approaches for combining experimental and computational fluid dynamics data sets

In this study multi-fidelity surrogate modelling for combining data sets of wind tunnel experiments and computations is examined, dealing with different types of errors. Co- kriging regression is constructed with the low-fidelity sample data of the computations and the high-fidelity data of the wind tunnel experiments, and is compared with co-kriging and polynomial response surface approaches. Face-centred central composite design is used to obtain the high-fidelity sample data for the co-kriging and co-kriging regression, where a blocking method is used to prevent systematic error between block boundaries. A randomisation method is for the wind tunnel experiments to reduce systematic error. Co-kriging regression has the potential to reduce the effect of systematic error working with randomisation method. The test case of a race car wing in ground effect is used here, and shows that while the polynomial response surface can not indicate a local optimum, the co-kriging and co-kriging regression do identify the twin optima that can be explored in more detail by adding sample points. The co-kriging regression shows a lower root mean square error compared to the other approximations. For assessing the confidence of surrogate models, the combined uncertainty of the approximations is shown, comprising the modelling uncertainty and the sample data uncertaint

Plant root PET: visualization of photosynthate translocation to roots in rice plant

Abstract Roots are essential to plants for uptake of water and nutrients. For the improvement of crop production, it is necessary to understand the elucidation of the root development and its function under the ground. Especially, photosynthate translocation from plant leaves to roots is an important physiological function that affects the root elongation, adaptation to the soil environment and nutrients uptake. To evaluate the translocation dynamics to roots, positron emission tomography (PET) and 11C tracer have been used. However, the spatial resolution is degraded at roots that develop around the peripheral area of field of view (FOV) due to parallax errors. In this study, to overcome this problem, we developed a small OpenPET prototype applying four-layer depth-of-interaction detectors. We demonstrated the imaging capability of 11C-photosynthate translocation to rice roots that develop throughout the entire PET field. We also tried to obtain structural information of roots by high-throughput X-ray computerized tomography (CT) system using the same test plant. As a result, we succeeded in visualizing the root structure that developed around the peripheral region of FOV and imaging the accumulation of 11C-photosynthate to the roots in those areas without degrading the spatial resolution. From obtained images, we also succeeded in evaluating the translocation dynamics varied by roots. The combined use of the high-throughput CT system and the OpenPET prototype was demonstrated to be appropriate for structural and functional analysis of roots.</jats:p