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Background: Despite significant limitations of growth medium reuse, a large amount of organic substrate is reused in soilless cultivation of horticultural crops in China. Arbuscular mycorrhizal fungi (AMF) can promote nutrient absorption and improve plant tolerance to biotic and abiotic stresses. However, the mechanisms governing the effects of AMF on crop growth in organic continuous cropping substrates have not been elucidated. Results: In this study, we showed that the inoculation of AMF in continuous cropping substrates promoted growth and root development, and increased the root and NADP-malic enzyme (NADP-ME) activity of tomato seedlings. Root transcriptome analysis demonstrated that the plant hormone signal transduction pathway was highly enriched, and 109 genes that positively correlated with the AMF-inoculated plant phenotype were obtained by gene set enrichment analysis (GSEA), which identified 9 genes related to indole acetic acid (IAA). Importantly, the levels of endogenous IAA in tomato seedlings significantly increased after AMF inoculation. Furthermore, the application of AMF significantly increased the expression levels of NADP-ME1 and NADP-ME2, as well as the activity of NADP-ME, and enhanced the root activity of tomato seedlings in comparison to that observed without inoculation of AMF. However, these effects were blocked in plants treated with 2,3,5-triiodobenzoic acid (TIBA), a polar transport inhibitor of IAA. Conclusions: These results suggest that IAA mediates the AMF-promoted tomato growth and expression of NADP-MEs in continuous cropping substrates. The study provides convincing evidence for the reuse of continuous cropping substrates by adding AMF as an amendment. [ABSTRACT FROM AUTHOR]

The first seasonal harvest technology of ratoon rice requires the least rolling with suitable stubble height required by agronomy when the ratoon rice is nearly mature. Mechanized harvesting in the first season of ratoon rice needs to finish harvesting, threshing, cleaning, straw treatment, grain transportation, grain collection and other processes at one time with a low rolling rate and low rolling degree. Limited by the production conditions such as wet and soft fields, and wet, thick and strong straw, harvest technology with high efficiency and a low rolling rate of ratoon rice in the first season has become the key technology and research focus affecting the yield of ratoon rice. In this paper, we analyzed the planting and popularization of ratoon rice in China, summarized the planting mode and agronomic characteristics of ratoon rice, highlighted the research status of mechanized harvesting equipment for the first season of ratoon rice, especially the specialized harvesters, and illustrated in detail the technical characteristics and research trends of key segments such as chassis, header, and processes such as threshing and cleaning, and straw and stubble treatment of ratoon rice harvesters. In addition, we summarized the application status and value of lightweight technology, performance monitoring and fault diagnosis technology, grain quality detection technology and automatic navigation technology of mechanized harvest in the first season, explained the main problems and reasons affecting the development of ratoon rice harvest mechanization in China, and illustrated the prospect of its research focus and tendency. [ABSTRACT FROM AUTHOR]

Barchan dunes are common on Earth, Mars and Titan. Previous studies have shown that their formation, migration and evolution are influenced by the wind regime and other factors, but details vary among regions. Understanding barchan morphology and migration will both improve our understanding of dune geomorphology and provide a basis for describing the environmental conditions that affect the formation and development of these dunes on Earth and other planets. Here, we provide detailed measurements of barchan dune migration in China's Quruq Desert, in the lower reaches of the Tarim River. We monitored their migration direction and rate, and their morphological changes during migration, by comparing Google Earth images acquired in 2003 and 2014. The dunes migrated west‐southwest, close to the local resultant drift direction. The migration rate averaged 8.9 to 32.1 m year−1, with obvious spatial variation. In addition to the wind regime, the migration rate depended on dune morphology, density and vegetation cover; the rate was negatively related to dune height, density and vegetation cover, but positively linearly related to the length/width ratio (LU/W) and to the decrease in this ratio from 2003 to 2014. We found correlations among the dune morphometric parameters, but the relationships were weaker than in previous research. Due to the complexity of the factors that affect the processes that underlie sand dune development and migration, the morphological changes during dune migration were also complex. Our measurements suggest that the aeolian environment played a dominant role in dune migration and its spatial variation in the Quruq Desert. These results will support efforts to control dune migration in the western Quruq Desert and improve our understanding of dune morphodynamics. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Fertile islands are created and maintained by a combination of physical and biologically mediated processes. Plants have been shown to be very important in the formation of fertile islands, and recent research indicates that the activities of burrowing animals have a significant influence on the physiochemical properties of soil that can promote the development of fertile islands. In this paper, we chose tamarisk ( Tamarix spp.)-a constructive species that grows in the oasis-desert ecotone, and the great gerbil ( Rhombomys opimus)-a widely distributed rodent in Central Asia to study the influence of great gerbils on soil nutrient dynamics in tamarisk mounds. Results indicate that fertile islands exist in tamarisk mounds without burrows of the great gerbil. However, the great gerbil's burrowing activities promote the fertile island effect in tamarisk mounds: soil nutrients under shrubs with great gerbil activity were significantly higher than inter-mound areas in both surface soil and deep soil from 15 to 50 cm. Available nitrogen in mounds with rodent burrows was over twice as high as in tamarisk mounds without burrows at the same depth. The great gerbil's burrowing activities promote the concentration of soil nutrients in the tamarisk mounds. [ABSTRACT FROM AUTHOR]