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Leaf senescence is an important process of growth and development in plant, and it is a programmed decline controlled by a series of genes. In this study, the biochemical properties and transcriptome at five maturity stages (M1∼M5) of tobacco leaves were analyzed to reveal the dynamic changes in leaf senescence of tobacco. A total of 722, 1,534, 3,723, and 6,933 genes were differentially expressed (DEG) between M1 and M2, M1 and M3, M1 and M4, and M1 and M5, respectively. Significant changes of nitrogen, sugars, and the DEGs related to metabolite accumulation were identified, suggesting the importance of energy metabolism during leaf senescence. Gene Ontology (GO) analysis found that DEGs were enriched in biosynthetic, metabolic, photosynthesis, and redox processes, and especially, the nitrogen metabolic pathways were closely related to the whole leaf senescence process (M1∼M5). All the DEGs were grouped into 12 expression profiles according to their distinct expression patterns based on Short Time-series Expression Miner (STEM) software analysis. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis found that these DEGs were enriched in pathways of carbon metabolism, starch and sucrose metabolism, nitrogen metabolism, and photosynthesis among these expression profiles. A total of 30 core genes were examined by Weight Gene Co-expression Network Analysis (WGCNA), and they appeared to play a crucial role in the regulatory of tobacco senescence. Our results provided valuable information for further functional investigation of leaf senescence in plants. [ABSTRACT FROM AUTHOR]

Melatonin is a well-known signaling molecule that mediates a range of physiological activities and various stress reactions in plants. We comprehensively tested the effect of melatonin on the development of root hairs and glandular trichomes and found that melatonin pretreatment of tobacco seeds significantly increased the length of root hairs. Furthermore, melatonin-treated tobacco exhibited significantly higher density of trichomes and larger glandular heads on long-stalk glandular trichomes than untreated plants, which resulted in enhanced secretion in glandular trichomes. Exogenous melatonin enhanced the aphid resistance of plants by facilitating the accumulation of cembranoids in the glandular trichomes and alleviated cadmium toxicity by increasing the Cd-exudation capacity of long glandular trichomes. Metabolic analysis indicated that the contents of 108 metabolites significantly changed upon melatonin treatment, with the contents of those that are directly/indirectly involved in melatonin metabolism changing the most. Further, KEGG pathway analysis suggested that the metabolic pathways of amino acids, reducing sugar, secondary metabolites, indole alkaloid biosynthesis, purine, pyrimidine, and ABC transporters were greatly influenced by exogenous melatonin application. Moreover, metabolisms of melatonin-related antioxidants and pyrimidine nucleoside antibiotics were enhanced after melatonin treatment. Melatonin improved tobacco resistance to high salinity, drought, and extreme temperature stresses, as indicated by improved photosynthetic and antioxidant capacities in treated vs. untreated plants. This study lays a foundation for the comprehensive application of melatonin to increase the stress tolerance of plants. [Display omitted] • Melatonin promoted the development of root hairs and glandular trichomes. • Exogenous melatonin enhanced aphid resistance of tobacco plants. • Melatonin facilitated the secretion of glandular trichomes. • Melatonin treatment alleviated cadmium toxicity in tobacco plants. • Exogenous melatonin enhanced the metabolism of some antioxidants. [ABSTRACT FROM AUTHOR]

The ∼800 km long Heihe River in northwestern China originates from the North Qilian Mountain, and passes through the Beishan Mountain before it reaches the Juyanhai Lake. Geologically, the river crosscuts the North Qilian Orogenic Belt, the Alax Terrane, and the Beishan Orogenic Belt. LA-ICP-MS U-Pb dating of detrital zircon from Heihe River sediments shows four age groups: 2700–1700 Ma, 1700–650 Ma, 650–358 Ma, and 358–230 Ma, and age peaks at ∼2450 Ma, ∼1850 Ma, ∼950 Ma, ∼520 Ma, 505 Ma, ∼480 Ma, ∼450 Ma, ∼430 Ma, ∼380 Ma, ∼320 Ma, and ∼295 Ma. The age distribution patterns indicate that Heihe River sediments were mainly sourced from the North Qilian Orogenic Belt. The detrital zircon ages demonstrate that the North Qilian Orogenic Belt may have Archean to late Paleoproterozoic rocks. Several tectonothermal events are also identified: opening of the North Qilian Ocean (part of the Paleo-Tethys Ocean) at early Neoproterozoic, subduction of oceanic lithosphere and formation of a trench-arc-basin system at late Neoproterozoic to late Ordovician, closure of the oceanic basin at late Ordovician, and collision of the Qaidam and Alax terranes at early Devonian. Our study indicates that the formation of the North Qilian Orogenic Belt was mainly related to the formation and closure of the Paleo-Tethys Ocean. [ABSTRACT FROM AUTHOR]

Heavy metal contamination from electroplating wastewater is a serious risk to terrestrial life and public health. The complexed metal cannot be effectively removed by traditional precipitation without decomplexing. In this work, four ozone-based advanced oxidation processes, O 3 , O 3 /H 2 O 2 , O 3 /UV and O 3 /H 2 O 2 /UV to decomplex electroplating wastewater were investigated and their performance compared. Ethylenediaminetetraacetic acid (EDTA) and citric acid are the most common components of electroplating wastewater. They were used as representatives to study the decomplexation and mineralization of complexes in the ozone-based advanced oxidation processes. Among all, the highest degradation and mineralization efficiency of EDTA occurred in O 3 /UV and was 65% and 53% in 60 min, respectively. For citric acid, the highest degradation (77%) and mineralization (56%) efficiency was observed in the O 3 /H 2 O 2 /UV process. This indicates that selection of the advanced oxidation process is determined by the target contaminant.