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Homeostasis of the essential micronutrient manganese (Mn) is crucially determined through availability and uptake efficiency in all organisms. Mn deficiency of plants especially occurs in alkaline and calcareous soils, seriously restricting crop yield. However, the mechanisms underlying the sensing and signaling of Mn availability and conferring regulation of Mn uptake await elucidation. Here, we uncover that Mn depletion triggers spatiotemporally defined long-lasting Ca2+ oscillations in Arabidopsis roots. These Ca2+ signals initiate in individual cells, expand, and intensify intercellularly to transform into higher-order multicellular oscillations. Furthermore, through an interaction screen we identified the Ca2+-dependent protein kinases CPK21 and CPK23 as Ca2+ signal-decoding components that bring about translation of these signals into regulation of uptake activity of the high-affinity Mn transporter natural resistance associated macrophage proteins 1 (NRAMP1). Accordingly, a cpk21/23 double mutant displays impaired growth and root development under Mn-limiting conditions, while kinase overexpression confers enhanced tolerance to low Mn supply to plants. In addition, we define Thr498 phosphorylation within NRAMP1 as a pivot mechanistically determining NRAMP1 activity, as revealed by biochemical assays and complementation of yeast Mn uptake and Arabidopsis nramp1 mutants. Collectively, these findings delineate the Ca2+-CPK21/23-NRAMP1 axis as key for mounting plant Mn homeostasis.

This research focused on the feasibility and stability of applying the forward and reverse combustion approach to the in situ gasification of lignite and bituminous coal with oxygen or oxygen–steam mixtures as gasification agents, especially reverse combustion gasification. A high-quality syngas (H2 and CO) could be obtained using the reverse combustion gasification technique combined with forward combustion gasification in a pilot system for in situ gasification. The gasification time was extended more than 25% using the reverse combustion approach. The controlling conditions for reverse combustion gasification were obtained by comparing and analyzing experimental data. The results show the relationship between the inject gas flow within certain limits and velocity of the gasification flame was linear during reverse combustion. The underground conditions of the coal seam and strata were simulated in a pilot-scale underground gasifier during experiments. The combustion gasification of coal was carried out experimentally for over 5 days. The average effective content (H2 and CO) of syngas was in the range of 60–70%, meeting the requirement of synthesis gas. The optimal ranges of gasifying lignite and bituminous coal were found to be 1.5–2.0 and 1.3–1.75, respectively. The product gas flow was proportional to oxygen blast. These are expected to provide useful guidance on practical underground coal gasification operations and to give experimental evidence in support of theory.

This research focused on the feasibility of applying the forward and reverse combustion approach to the in situ gasification of lignite with the production of hydrogen-rich syngas (H2 and CO). The so-called forward combustion gasification (FCG) and reverse combustion gasification (RCG) approach in which oxygen and steam are simultaneously fed to the simulated system of underground coal gasification (UCG) was studied. A simulated system of UCG was designed and established. The underground conditions of the coal seam and strata were simulated in the system. The combustion gasification of lignite has been carried out experimentally for almost 6.5 days. The average effective content (H2 + CO) of syngas during the FCG phase was 62.31 % and the maximum content was 70.92 %. For the RCG phase the corresponding figures are 61.33 % and 67.91 %. Thus, the feasibility of using RCG way for UCG has been demonstrated. The temperature profiles have been provided by using of 85 thermocouples during the model experiment, which portrayed the several nephograms of thermal data in the gasifier were of significance for the prospective gasification processes.