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In order to reveal the effect of matrix cracks resulted from thermal residual stresses (TRS) on the thermal expansion behavior of ceramic matrix composites, SiBC matrix was introduced into Cf/SiC and SiCf/SiC by liquid silicon infiltration. The TRS in both two composites were enlarged with incorporating SiBC matrix which has higher coefficients of thermal expansion (CTEs) than SiC matrix. Due to the relatively high TRS, matrix cracks and fiber/matrix (f/m) debonding exist in Cf/SiC-SiBC, which would provide the space for the expansion of matrix with higher CTEs. For SiCf/SiC, no matrix cracking and f/m debonding took place due to the close CTEs between fiber and matrix. Accordingly, with the incorporation of SiBC matrix, the in-plane CTE of Cf/SiC between room temperature to 1100 °C decreases from 3.65 × 10−6 to 3.19 × 10−6 K-1, while the in-plane CTE of SiCf/SiC between room temperature to 1100 °C increases slightly from 4.97 × 10−6 to 5.03 × 10−6 K-1.

In this paper, carbon fibre reinforced SiC–Si dual matrix composites (C/SiC–Si) with two-dimensional (2D) and three-dimensional needled (3DN) preforms were prepared. Compared with the 3DN preform, there was a higher effective volume fraction of carbon fibre (20 vol%) in the loading direction for the 2D preform, leading to higher flexural strength (348 ± 29 MPa) and fracture toughness (15.0 ± 1.7 MPa·m1/2) of the 2D C/SiC–Si. The silicon agglomerated in the inter-bundle area to form a silicon pool in the 2D preform, and thus the silicon melt can easily be scoured by the heat flux. The silicon uniformly dispersed in the SiC matrix of the 3DN preform, which can allow them to protect each other in the ablation process, and thus the 3DN C/SiC–Si had a lower mass ablation rate (6.2 mg∙s-1) than the 2D C/SiC–Si (12.3 mg∙s-1).

Abscisic acid (ABA) is a critical hormone for plant survival upon water stress. In this study, a large-scale mutants of Arabidopsis ecotype Columbia-0 (Col-0) by ethyl methanesulfonate (EMS)-mutagenesis were generated, and an improved root elongation under water-stress 1 (irew1) mutant showing significantly enhanced root growth was isolated upon a water potential gradient assay. Then, irew1 and ABA-related mutants in Arabidopsis or tomato plants were observed under water potential gradient assay or water-deficient condition. ABA pathway, Ca

Soil drying enhances root ABA accumulation and rhizosheath formation, but whether ABA mediates rhizosheath formation is unclear. Here, we used the ABA-deficient mutant Az34 to investigate molecular and morphological changes by which ABA could affect rhizosheath formation. Mild soil drying with intermittent watering increased rhizosheath formation by promoting root and root hair elongation. Attenuated root ABA accumulation in Az34 barley constrained the promotion of root length and root hair length by drying soil, such that Az34 had a smaller rhizosheath. Pharmacological experiments of adding fluridone (an ABA biosynthesis inhibitor) and ABA to drying soil restricted and enhanced rhizosheath formation respectively in Az34 and wild-type Steptoe barley. RNA sequencing suggested that ABA accumulation mediates auxin synthesis and responses and root and root hair elongation in drying soil. In addition, adding indole-3-acetic acid (IAA) to drying soil increased rhizosheath formation by promoting root and root hair elongation in Steptoe and Az34 barley. Together, these results show that ABA accumulation induced by mild soil drying enhance barley rhizosheath formation, which may be achieved through promoting auxin response. © 2021 John Wiley & Sons Ltd.

Root and rhizosphere is important for phosphorus (P) uptake in rice plants. However, little is known about the detailed regulation of irrigation regimes, especially frequently alternate wetting and drying (FAWD), on P usage of rice plants. Here, we found that compared with normal water and P dose, FAWD with a reduced P dose maintained the grain yield in two rice varieties. Compared to rice variety Gaoshan1, rice variety WufengyouT025 displayed a higher grain yield, shoot P content, rhizosphere acid phosphatase activity, abundance of bacteria, and bacterial acid phosphatase gene of rhizosphere. Moreover, the FAWD regime may increase the abundance of bacteria with acid phosphatase activity to release available phosphorus in the rhizosphere, which is associated with rice varieties. Our results suggest that an optimized management of irrigation and phosphorous application can enhance both water and phosphorus use efficiency without sacrificing the yield, which may contribute significantly to sustainable agriculture production.

Microwave absorption materials (MAMs) with lightweight density and ultrabroad-band microwave absorption performance are urgently needed in advanced MAMs, which are still a big challenge and have been rarely achieved. Here, a new wide bandwidth absorption model was designed, which fuses the electromagnetic resonance loss ability of a periodic porous structure in the low-frequency range and the dielectric loss ability of dielectric materials in the high-frequency range. Based on this model, a lightweight porous cellulose nanofiber (CNF)/carbon nanotube (CNT) foam consisting of a cellular vertical porous architecture with the macropore diameters between 30 and 90 μm and a nanoporous architecture at a scale of 1.7-50 nm was obtained by an ice-template method using CNTs and CNFs as "building blocks". Benefiting from the unique architecture, the effective absorption bandwidth reaches 29.7 GHz, and its specific microwave absorption performance exceeds 80,000 dB·cm-2·g-1, which far surpasses those of the MAMs previously reported, including all CNT-based composites. Moreover, the CNF/CNT foam possesses ultralow density (9.2 mg/cm3) and strong fatigue resistance, all coming from the well-interconnected porous structure and the strong hydrogen bonds among CNF-CNF and CNF-CNT molecular chains.

High-performance carbon nanotubes (CNTs) with adjustable electro-conductivity have been widely used as electromagnetic (EM) waves absorption materials to achieve stealth of weapons and equipment. Chemical vapor deposition technology is used for the simple preparation of CNTs on porous Sc2Si2O7 matrix. As expected, well-matched impedance and EM dissipation of CNTs/Sc2Si2O7 ceramics are synthesized. Curls of CNTs formed a three-dimensional network structure and large amounts of interfaces, resulting in multiple reflections and scattering of EM waves. The defect concentrations can be optimized by tuning reaction times. The existing defects will produce dipole polarization and affect the band gap of CNTs as well. Using density functional theory as first principle calculations, we calculate and simulate the relationship between band gap and vacancy-defects of CNTs. The results show that the appropriate contents of vacancy-defects will increase the band gap of CNTs, which regulate the conductivity loss of CNTs/Sc2Si2O7. Hence, the excellent microwave absorption performance of CNTs/Sc2Si2O7 (loading content of 1.56 wt%) is RCmin of −33.5 dB at the thickness of 2.85 mm, achieving an effective absorbing bandwidth of 4.2 GHz covering the whole X-band. The exploration results provide a useful reference to EM wave absorption materials with strong absorption, wide bandwidth and thin thickness.

For enhancing the absorption ability of dielectric and electromagnetic wave (EMW), C-rich SiC NWs /Sc 2 Si 2 O 7 ceramics are successfully fabricated through in-situ growth of SiC nanowires (NWs) into porous Sc 2 Si 2 O 7 ceramics by precursor infiltration and pyrolysis (PIP) at 1400 °C in Ar. SiC NWs are in-situ formed in the pore channels via a vapor-liquid-solid (VLS) mechanism, the relative complex permittivity increases notably with the content of absorber (C-rich SiC NWs), which tune the microstructure and dielectric property of C-rich SiC NWs/Sc 2 Si 2 O 7 ceramics. Meanwhile, the minimum reflection coefficient (RC) of C-rich SiC NWs/Sc 2 Si 2 O 7 ceramic decreases from −9.5 dB to − 35.5 dB at 11 GHz with a thickness of 2.75 mm, and the effective absorption bandwidth (EAB) covers the whole X band (8.2–12.4 GHz) when the content of absorber is 24.5 wt%. The results indicate that Sc 2 Si 2 O 7 ceramics decorated with SiC NWs and nanosized carbon have a superior microwave-absorbing ability, which can be contributed to the Debye relaxation, interfacial polarization and conductivity loss enhanced by in-situ formed SiC NWs and nanosized carbon phases. The C-rich SiC NWs /Sc 2 Si 2 O 7 ceramics can be a promising microwave absorbing materials within a broad bandwidth.

[EN] The hab1-1abi1-2abi2-2pp2ca-1 quadruple mutant (Qabi2-2) seedlings lacking key negative regulators of ABA signaling, namely, clade A protein phosphatases type 2C (PP2Cs), show more apoplastic H+ efflux in roots and display an enhanced root growth under normal medium or water stress medium compared to the wild type. The presence of low ABA concentration (0.1 micromolar), inhibiting PP2C activity via monomeric ABA receptors, enhances root apoplastic H+ efflux and growth of the wild type, resembling the Qabi2-2 phenotype in normal medium. Qabi2-2 seedlings also demonstrate increased hydrotropism compared to the wild type in obliquely-oriented hydrotropic experimental system, and asymmetric H+ efflux in root elongation zone is crucial for root hydrotropism. Moreover, we reveal that Arabidopsis ABA-insensitive 1, a key PP2C in ABA signaling, interacts directly with the C terminus of Arabidopsis plasma membrane H+-dependent adenosine triphosphatase 2 (AHA2) and dephosphorylates its penultimate threonine residue (Thr(947)), whose dephosphorylation negatively regulates AHA2., We are grateful for grant support from the National Key R&D Program of China (2017YFE0118100 and 2018YFD02003025), National Natural Science Foundation of China (nos. 31600209, 31761130073, and 31872169), a Newton Advanced Fellowship (NSFC-RS: NA160430), Fujian Province Education Department Funding (JK2017015), and Research Grant of FAFU (KXGH17005). Work in the laboratory of P.L.R. was supported by the Ministerio de Ciencia, Innovacion y Universidades (MICIU), grant BIO2017-82503-R.

Abscisic acid (ABA) is a critical hormone for plant survival under water stress. In this study, large-scale mutants of the Arabidopsis ecotype Columbia-0 (Col-0) were generated by ethyl methanesulfonate (EMS)-mutagenesis, and an improved root elongation under water-stress 1 (irew1) mutant showing significantly enhanced root growth was isolated under a water potential gradient assay. Then, irew1 and ABA-related mutants in Arabidopsis or tomato plants were observed under water potential gradient assay or water-deficient conditions. ABA pathway, Ca2+ response, and primary root (PR) elongation rate were monitored in addition to DNA- and RNA-Seq analyses. We found that based on phenotyping and transcriptional analyses, irew1 exhibited enhanced PR growth, ABA, and Ca2+ responses, compared to wild type subjected to water stress. Interestingly, exogenous Ca2+ application enhanced PR growth of irew1, ABA-biosynthesis deficient mutants in Arabidopsis, and tomato plants, in response to water potential gradients or water-deficient conditions. In combination with other ABA-related mutants and pharmacological studies, our results suggest that ABA is required for root elongation associated with Ca2+ influx in response to water stress.

Hydrotropism is the directed growth of roots toward the water found in the soil. However, mechanisms governing interactions between hydrotropism and gravitropism remain largely unclear. In this study, we found that an air system and an agar–sorbitol system induced only oblique water-potential gradients; an agar–glycerol system induced only vertical water-potential gradients; and a sand system established both oblique and vertical water-potential gradients. We employed obliquely oriented and vertically oriented experimental systems to study hydrotropism in Arabidopsis and tomato plants. Comparative analyses using different hydrotropic systems showed that gravity hindered the ability of roots to search for obliquely oriented water, whilst facilitating roots’ search for vertically oriented water. We found that the gravitropism-deficient mutant aux1 showed enhanced hydrotropism in the oblique orientation but impaired root elongation towards water in the vertical orientation. The miz1 mutant exhibited deficient hydrotropism in the oblique orientation but normal root elongation towards water in the vertical orientation. Importantly, in contrast to miz1, the miz1/aux1 double mutant exhibited hydrotropic bending in the oblique orientation and attenuated root elongation towards water in the vertical orientation. Our results suggest that gravitropism is required for MIZ1-regulated root hydrotropism in both the oblique orientation and the vertical orientation, providing further insight into the role of gravity in root hydrotropism.

In this work, Ti3SiC2-based ceramics were fabricated by the infiltration of liquid silicon into TiC preform by incorporating a small amount of Al. Al can play a catalytic role to promote the formation of TiC twins before liquid silicon infiltration (LSI), which leads to the increase of transformation efficiency from TiC to Ti3SiC2 in the LSI process. When the Al content in the TiC preform increases to 9 wt.%, the volume content of Ti3SiC2 reaches 85 vol.%, revealing the high electromagnetic interference shielding effectiveness of 39 dB in the frequency range of 8.2–12.4 GHz. The results indicate that it is an effective way to synthesize Ti3SiC2-based ceramics with excellent electromagnetic shielding performance.

In natural environments, shoot was exposed to sunlight but roots are not directly exposed to light, being buried deep down in the soil and grow in darkness without sucrose addition. However, most current research in root biology has been carried out by growing the Arabidopsis root system in the presence of light and sucrose-added medium since root development is typically studied in traditional agar-plate culture system (TPG, traditional plant-growing). Here, we present a protocol for improved agar-plate culture system (IPG, improved plant-growing), allows the in vitro cultivation of Arabidopsis with the aerial part growing in normal light/dark photoperiod while roots grow in darkness without sucrose addition. IPG provides an efficient system for cultivating a large number of seedlings and easily characterizing root architecture in the dark. We also provide methods for key steps all the way through to seedlings growth.We found that the primary root lengths in TPG were significantly longer than that in IPG, and the root elongation growth is dependent on auxin-triggered acidification of the root apoplast of Arabidopsis . With this protocol, a better understanding of the mechanisms involved in root growth and responses of plants can be easily characterized.

In this work, Ti3SiC2-based ceramics were fabricated by the infiltration of liquid silicon into TiC preform by incorporating a small amount of Al. Al can play a catalytic role to promote the formation of TiC twins before liquid silicon infiltration (LSI), which leads to the increase of transformation efficiency from TiC to Ti3SiC2 in the LSI process. When the Al content in the TiC preform increases to 9 wt.%, the volume content of Ti3SiC2 reaches 85 vol.%, revealing the high electromagnetic interference shielding effectiveness of 39 dB in the frequency range of 8.2&ndash, 12.4 GHz. The results indicate that it is an effective way to synthesize Ti3SiC2-based ceramics with excellent electromagnetic shielding performance.

Hydrogen peroxide (H2O2) and nitric oxide (NO) are key signaling molecules in cells whose levels are increased in response to various stimuli and are involved in plant secondary metabolite synthesis. In this paper, the roles of H2O2 and NO on salvianolic acid B (Sal B) production in salicylic acid (SA)-induced Salvia miltiorrhiza cell cultures were investigated. The results showed that H2O2 could be significantly elicited by SA, even though IMD (an inhibitor of NADPH oxidase) or DMTU (a quencher of H2O2) were employed to inhibit or quench intracellular H2O2. These elicited H2O2 levels significantly increased NO production by 1.6- and 1.46 fold in IMD+SA and DMTU+SA treatments, respectively, and induced 4.58- and 4.85-fold Sal B accumulation, respectively. NO was also markedly elicited by SA, in which L-NNA (an inhibitor of NO synthase) and cPTIO (a quencher of NO) were used to inhibit or quench NO within cells, and the induced NO could significantly enhance H2O2 production by 1.92- and 1.37-fold in L-NNA+SA and cPTIO+SA treatments, respectively, and 3.27- and 1.50-fold for Sal B accumulation, respectively. These results indicate that elicitation of SA for either H2O2 or NO was independent, and the elicited H2O2 or NO could act independently or synergistically to induce Sal B accumulation in SA-elicited cells.

In order to study the effects of Ca2+ in the biosynthesis of salvianolic acid B (Sal B) induced by salicylic acid (SA) in the young seedlings of Salvia miltiorrhiza, we used confocal laser scanning microscopy and high performance liquid chromatography to measure the change of relative fluorescence intensity of Ca2+ and the contents of Sal B induced by SA before and after the application of extracellular calcium channel inhibitors (VP and LaCl3), intracellular calcium channel inhibitor (LiCl), as well as intracellular calmodulin antagonist (TFP). SA could induce the calcium burst, and the Ca2+ peak could last to 2-3 min in the guard cells of S. miltiorrhiza, which prompted the biosynthesis of Sal B after the Ca2+ burst. Both Vp or LaCl3, and LiCl or TFP could inhibit the burst of Ca2+ and the biosynthesis of Sal B. The above results demonstrated that Ca2+ from the extracellular and the intracellular calcium store regulate the biosynthesis of Sal B elicited by salicylic acid in S. miltiorrhiz young seedlings.

We studied the influence of the concentration of Ca2+ (0-50 mmol/L) in culture medium on the synthesis of rosmarinic acid (RA) and related enzymes in Salvia miltiorrhiza suspension cultures. Using verpamil (VP, a calcium channel antagonist) and ionophore A23187, we studied the mechanism of secondary metabolites of Salvia miltiorrhiza suspension cultures influenced by the concentration of Ca2+ in the culture medium. The synthesis of intracellular RA in 6-day incubation was significantly dependent on the medium Ca2+ concentration. At the optimal Ca2+ concentration of 10 mmol/L, a maximal RA content of 20.149 mg/g biomass dry weight was reached, which was about 37.3% and 20.4% higher than that at Ca2+ concentrations of 1 and 3 mmol/L, respectively. The variation of the activity of PAL and TAT, two key enzymes of the two branches of RA, could be affected by the concentration of Ca2+ in culture medium. The change of their activity occurred prior to the accumulation of RA, which suggested both of the key enzymes be involved in the synthesis of RA. Meanwhile, the enzymatic action of PAL was more distinct than TAT. The treatment of VP and A23187, respectively, indicated that the influence of RA affected by the concentration of Ca2+ in the culture medium was accomplished by the intracellular Ca2+, and the flow of Ca2+ from the extracellular to the intracellular environment could also participate in this process.