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The lenticel is a channel-like structure that facilitates oxygen, carbon dioxide, and water vapor exchange on secondary growth tissue, such as a tree stem. Although the structure of lenticel has been described, there is limited understanding regarding the impact of this secondary structure on secondary growth as well as the cellular and metabolic processes underlying its formation. The study reveals the essential role of the lenticel in the process of tree secondary growth and the cellular and metabolic processes that take place during its formation. Under the stomata, lenticel development occurs when cells divide and differentiate into a structure of disconnected cells with air spaces between them. During lenticel formation, specific metabolic pathways and wax biosynthesis are activated. The SERK (somatic embryogenesis receptor kinase) gene controls lenticel density, and serk1serk3serk5 triple mutants enhance lenticel initiation. The findings shed light on the cellular and metabolic processes involved in lenticel formation, laying the groundwork for further mechanistic elucidation of their development, function, and genetic regulation in trees.

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The electron extraction from perovskite/C60 interface plays a crucial role in influencing the photovoltaic performance of inverted perovskite solar cells (PSCs). Here, we develop a one-stone-for-three-birds strategy via employing a novel fullerene derivative bearing triple methyl acrylate groups (denoted as C60-TMA) as a multifunctional interfacial layer to optimize electron extraction at the perovskite/C60 interface. It is found that the C60-TMA not only passivates surface defects of perovskite via coordination interactions between C=O groups and Pb2+ cations but also bridge electron transfer between perovskite and C60. Moreover, it effectively induces the secondary grain growth of the perovskite film through strong bonding effect, and this phenomenon has never been observed in prior art reports on fullerene related studies. The combination of the above three upgrades enables improved perovskite film quality with increased grain size and enhanced crystallinity. With these advantages, C60-TMA treated PSC devices exhibit a much higher power conversion efficiency (PCE) of 24.89% than the control devices (23.66%). Besides, C60-TMA benefits improved thermal stability of PSC devices, retaining over 90% of its initial efficiency after aging at 85 °C for 1200 h, primarily due to the reinforced interfacial interactions and improved perovskite film quality.

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Mn-based catalysts are promising candidates for eliminating harmful nitrogen oxides (NOx) via selective catalytic reduction with ammonia (NH3-SCR) due to their inherent strong redox abilities. However, poor water tolerance and low N2 selectivity are still the main limitations for practical applications. Herein, we succeeded in preparing an active catalyst for NH3-SCR with improved water tolerance and N2 selectivity based on protecting MnOx with a secondary growth of a hydrophobic silicalite-1. This protection suppressed catalyst deactivation by water adsorption. Interestingly, impregnating MnOx on MesoTS-1 followed by silicalite-1 protection allowed for a higher dispersion of MnOx species, thus increasing the concentration of acid sites. Consequently, the level of N2O formation is decreased. These improvements resulted in a broader operating temperature of NOx conversion and a modification of the NH3-SCR mechanism. Diffuse reflectance infrared Fourier transform spectroscopy analysis revealed that unprotected Mn/MesoTS-1 mainly followed the Eley-Rideal mechanism, while Mn/MesoTS-1@S1 followed both Langmuir-Hinshelwood and Eley-Rideal mechanisms.

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Membrane-based pervaporation (PV) for organic solvent dehydration is of great significance in the chemical and petrochemical industries. In this work, high-aluminum ZSM-5 zeolite membranes were synthesized by a fluoride-assisted secondary growth on α-alumina tubular supports using mordenite framework inverted (MFI) nanoseeds (~110 nm) and a template-free synthesis solution with a low Si/Al ratio of 10. Characterization by XRD, EDX, and SEM revealed that the prepared membrane was a pure-phase ZSM-5 zeolite membrane with a Si/Al ratio of 3.8 and a thickness of 2.8 µm. Subsequently, two categories of PV performance parameters (i.e., flux versus separation factor and permeance versus selectivity) were used to systematically examine the effects of operating conditions on the PV dehydration performance of different organic solvents (methanol, ethanol, n-propanol, and isopropanol), and their PV mechanisms were explored. Employing permeance and selectivity effectively disentangles the influence of operating conditions on PV performance, thereby elucidating the inherent contribution of membranes to separation performance. The results show that the mass transfer during PV dehydration of organic solvents was mainly dominated by the adsorption-diffusion mechanism. Furthermore, the diffusion of highly polar water and methanol molecules within membrane pores had a strong mutual slowing-down effect, resulting in significantly lower permeance than other binary systems. However, the mass transfer process for water/low-polar organic solvent (ethanol, n-propanol, and isopropanol) mixtures was mainly controlled by competitive adsorption caused by affinity differences. In addition, the high-aluminum ZSM-5 zeolite membrane exhibited superior PV dehydration performance for water/isopropanol mixtures.

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Populus, a significant fast-growing tree species with global afforestation and energy potential, holds considerable economic value. The abundant production of secondary xylem by trees, which serves as a vital resource for industrial purposes and human sustenance, necessitates the orchestration of various regulatory mechanisms, encompassing transcriptional regulators and microRNAs (miRNAs). Nevertheless, the investigation of microRNA-mediated regulation of poplar secondary growth remains limited. In this study, we successfully isolated a novel microRNA (Pag-miR257) from 84 K poplar and subsequently integrated it into the 35 S overexpression vector. The overexpression of Pag-miR257 resulted in notable increases in plant height, stem diameter, and fresh weight. Additionally, the overexpression of Pag-miR257 demonstrated a significant enhancement in net photosynthetic rate. The findings from the examination of cell wall autofluorescence indicated a substantial increase in both xylem area and the number of vessels in poplar plants overexpressing Pag-miR257. Furthermore, the cell wall of the Pag-miR257 overexpressing plants exhibited thickening as observed through transmission electron microscopy. Moreover, the Fourier Transforms Infrared (FTIR) analysis and phloroglucinol-HCl staining revealed an elevation in lignin content in Pag-miR257 overexpressing poplar plants. The findings of this study suggest that microRNA257 may play a role in the control of secondary growth in poplar stems, thereby potentially enhancing the development of wood engineering techniques for improved material and energy production.

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Secondary xylem and phloem originate from a lateral meristem called the vascular cambium that consists of one to several layers of meristematic cells. Recent lineage tracing studies have shown that only one of the cambial cells in each radial cell file functions as the stem cell, capable of producing both secondary xylem and phloem. Here, we first review how phytohormones and signalling peptides regulate vascular cambium formation and activity. We then propose how the stem cell concept, familiar from apical meristems, could be applied to cambium studies. Finally, we discuss how this concept could set the basis for future research.

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In the tropics, more precisely in equatorial dense rainforest, xylogenesis is driven by a little distinct climatological seasonality, and many tropical trees do not show clear growth rings. This makes retrospective analyses and modeling of future tree performance difficult. This research investigates the presence, the distinctness, and the periodicity of growth ring for dominant tree species in two semi-deciduous rainforests, which contrast in terms of precipitation dynamics. Eighteen tree species common to both forests were investigated. We used the cambial marking technique and then verified the presence and periodicity of growth-ring boundaries in the wood produced between pinning and collection by microscopic and macroscopic observation. The study showed that all eighteen species can form visible growth rings in both sites. However, the periodicity of ring formation varied significantly within and between species, and within sites. Trees from the site with clearly defined dry season had a higher likelihood to form periodical growth rings compared to those from the site where rainfall seasonality is less pronounced. The distinctness of the formed rings however did not show a site dependency. Periodical growth-ring formation was more likely in fast-growing trees. Furthermore, improvements can be made by a detailed study of the cambial activity through microcores taken at high temporal resolution, to get insight on the phenology of the lateral meristem.

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Pervaporation (PV), as an energy-efficient mixture separation technology, plays an important role in the chemical industry. In this work, no organic templates were needed to produce high-performance ZSM-5 membranes with an extremely low Si/Al ratio of 3.3 on α-Al2O3 tubular supports using 100 nm nanoseeds. The effects of preparation parameters on the crystalline phase structures, micromorphologies, and PV separation performance of ZSM-5 membranes were comprehensively investigated. The results revealed that the Si/Al ratio of gels significantly affected both the Si/Al ratio and the crystal orientation of the final ZSM-5 membrane. The optimized ZSM-5 membrane with a thickness of 1.8 µm was utilized to dehydrate various organic solvents via PV, and the influence of the operating parameters on PV dehydration performance was evaluated and is described herein. Furthermore, the permeation behaviors of single gases and PV were examined using permeate molecules within a similar size range to reveal the PV mechanism of the ZSM-5 membrane. The results demonstrated that gas permeation followed Knudsen diffusion, while PV permeation was decreased with decreases in the affinity of molecules, revealing an adsorption-diffusion mechanism that dominated PV dehydration through the ZSM-5 membrane. Moreover, the as-synthesized ZSM-5 membrane had good water permselectivity for water/acetone (e.g., total flux = 1.03 kg/(m2 h), α = 307) and for water/isopropanol (e.g., total flux = 1.49 kg/(m2 h), α = 1070) mixtures compared with other membranes reviewed in the literature. The synthesized ZSM-5 membrane also exhibited excellent reproducibility, high stability, and attractive PV separation performance, demonstrating its significant potential application in the PV dehydration of organic solvents.

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Wood formation, which occurs mainly through secondary xylem development, is important not only for supplying raw material for the 'ligno-chemical' industry but also for driving the storage of carbon. However, the complex mechanisms underlying the promotion of xylem formation remain to be elucidated. Here, we found that overexpression of Auxin-Regulated Gene involved in Organ Size (ARGOS) in hybrid poplar 84 K (Populus alba × Populus tremula var. glandulosa) enlarged organ size. In particular, PagARGOS promoted secondary growth of stems with increased xylem formation. To gain further insight into how PagARGOS regulates xylem development, we further carried out yeast two-hybrid screening and identified that the auxin transporter WALLS ARE THIN1 (WAT1) interacts with PagARGOS. Overexpression of PagARGOS up-regulated WAT1, activating a downstream auxin response promoting cambial cell division and xylem differentiation for wood formation. Moreover, overexpressing PagARGOS caused not only higher wood yield but also lower lignin content compared with wild-type controls. PagARGOS is therefore a potential candidate gene for engineering fast-growing and low-lignin trees with improved biomass production.

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Background: Panax ginseng, one of the valuable perennial medicinal plants, stores numerous pharmacological substrates in its storage roots. Given its perennial growth habit, organ regeneration occurs each year, and cambium stem cell activity is necessary for secondary growth and storage root formation. Cytokinin (CK) is a phytohormone involved in the maintenance of meristematic cells for the development of storage organs; however, its physiological role in storage-root secondary growth remains unknown. Methods: Exogenous CK was repeatedly applied to P. ginseng, and morphological and histological changes were observed. RNA-seq analysis was used to elucidate the transcriptional network of CK that regulates P. ginseng growth and development. The HISTIDINE KINASE 3 (PgHK3) and RESPONSE REGULATOR 2 (PgRR2) genes were cloned in P. ginseng and functionally analyzed in Arabidopsis as a two-component system involved in CK signaling. Results: Phenotypic and histological analyses showed that CK increased cambium activity and dormant axillary bud formation in P. ginseng, thus promoting storage-root secondary growth and bud formation. The evolutionarily conserved two-component signaling pathways in P. ginseng were sufficient to restore CK signaling in the Arabidopsis ahk2/3 double mutant and rescue its growth defects. Finally, RNA-seq analysis of CK-treated P. ginseng roots revealed that plant-type cell wall biogenesis-related genes are tightly connected with mitotic cell division, cytokinesis, and auxin signaling to regulate CK-mediated P. ginseng development. Conclusion: Overall, we identified the CK signaling-related two-component systems and their physiological role in P. ginseng. This scientific information has the potential to significantly improve the field-cultivation and biotechnology-based breeding of ginseng.

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Eucalyptus was one of the most cultivated hardwood species worldwide, with rapid growth, good wood properties and a wide range of adaptability. Eucalyptus stem undergoes primary growth (longitudinal growth) followed by secondary growth (radial growth), which produces biomass that is an important source of energy worldwide. In order to better understand the genetic regulation of secondary growth in Eucalyptus grandis, Transcriptome analyses in stem segments along a developmental gradient from the third internode to the eleventh internode of E. grandis that spanned primary to secondary growth were carried out. 5,149 genes that were differentially expressed during stem development were identified. Combining the trend analysis by the Mfuzz method and the module-trait correlation analysis by the Weighted Gene Co-expression Network Analysis method, a total of 70 differentially expressed genes (DEGs) selected from 868 DEGs with high connectivity were found to be closely correlated with secondary growth. Results revealed that the differential expression of these DEGs suggests that they may involve in the primary growth or secondary growth. AP1, YAB2 TFs and EXP genes are highly expressed in the IN3, whereas NAC, MYB TFs are likely to be important for secondary growth. These results will expand our understanding of the complex molecular and cellular events of secondary growth and provide a foundation for future studies on wood formation in Eucalyptus.

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Periderm is a well-known structural feature with vital roles in protection of inner plant tissues and wound healing. Despite its importance to plant survival, knowledge of periderm occurrences outside the seed plants is limited and the evolutionary origins of periderm remain poorly explored. Here, we review the current knowledge of the taxonomic distribution of periderm in its two main forms - canonical periderm (periderm formed as a typical ontogenetic stage) and wound periderm (periderm produced as a self-repair mechanism) - with a focus on major plant lineages, living and extinct. We supplement the published occurrences with data based on our own observations and experiments. This updated body of data reveals that the distribution of wound periderm is more widespread taxonomically than previously recognized and some living and extinct groups are capable of producing wound periderm, despite canonical periderm being absent from their normal developmental program. A critical review of canonical and wound periderms in extant and fossil lineages indicates that not all periderms are created equal. Their organisation is widely variable and the differences can be characterised in terms of variations in three structural features: (i) the consistency in orientation of periclinal walls within individual files of periderm cells; (ii) the lateral coordination of periclinal walls between adjacent cell files; and (iii) whether a cambial layer and conspicuous layering of inward and outward derivatives can be distinguished. Using a new system of scoring periderm structure based on these criteria, we characterise the level of organisation of canonical and wound periderms in different lineages. Looking at periderms through the lens provided by their level of organisation reveals that the traditional image of periderm as a single generalised feature, is best viewed as a continuum of structural configurations that are all predicated by the same basic process (periclinal divisions), but can fall anywhere between very loosely organized (diffuse periclinal growth) to very tightly coordinated (organized periclinal growth). Overall, wound periderms in both seed plants and seed-free plants have lower degrees of organisation than canonical periderms, which may be due to their initiation in response to inherently disruptive traumatic events. Wound and canonical periderms of seed plants have higher degrees of organisation than those of seed-free plants, possibly due to co-option of the programs responsible for organizing their vascular cambial growth. Given the importance of wound periderm to plant survival, its widespread taxonomic distribution, and its early occurrence in the fossil record, we hypothesise that wound periderm may have had a single origin in euphyllophytes and canonical periderm may have originated separately in different lineages by co-option of the basic regulatory toolkit of wound periderm formation. In one evolutionary scenario, wound periderm regulators activated initially by tissue tearing due to tensional stresses elicited by woody growth underwent heterochronic change that switched their activation trigger from tissue tearing to the tensional stresses that precede it, with corresponding changes in the signalling that triggered the regulatory cascade of periderm development from tearing-induced signals to signalling induced by tension in cells.

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Gibberellins (GAs) play a crucial role in regulating secondary growth in angiosperms, but their effects on the secondary growth of gymnosperms are rarely reported. In this study, we administered exogenous GA3 to two-year-old P. massoniana seedlings, and examined its effects on anatomical structure, physiological and biochemical changes, and gene expression in stems. The results showed that exogenous GA3 could enhance xylem development in P. massoniana by promoting cell division. The content of endogenous hormone (including auxins, brassinosteroids, and gibberellins) were changed and the genes related to phytohormone biosynthesis and signaling pathway, such as GID1, DELLA, TIR1, ARF, SAUR, CPD, BR6ox1, and CYCD3, were differentially expressed under GA3 treatment. Furthermore, GA3 and BR (brassinosteroid) might act synergistically in promoting secondary growth in P. massoniana. Additionally, lignin content was significantly increased after GA3 treatment accompanied by the express of lignin biosynthesis related genes. PmCAD (TRINITY_DN142116_c0_g1), a crucial gene involved in the lignin biosynthesis, was cloned and overexpressed in Nicotiana benthamiana, significantly promoting the xylem development and enhancing stem lignification. It was regarded as a key candidate gene for improving stem growth of P. massoniana. The findings of this study have demonstrated the impact of GA3 treatment on secondary growth of stems in P. massoniana, providing a foundation for understanding the molecular regulatory mechanism of stem secondary growth in Pinaceae seedlings and offering theoretical guidance for cultivating new germplasm with enhanced growth and yield.

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Secondary growth is a highly relevant process for dicot and gymnosperm species development. The process relies on vascular tissue proliferation and culminates with the thickening of stems, roots, and hypocotyls. The formation of tracheary elements is a critical step during this process. Among such tracheary elements, four different cell types are distinguished depending on their secondary cell wall pattern, which is exclusive for each tracheary cell type. Here we describe a method to isolate, dye, and recognize each of these tracheary cell types. The method is optimized to be performed in the Arabidopsis thaliana hypocotyl. This is because, in this species, the hypocotyl is the organ undergoing the largest proportion of secondary growth. Results allow for determining the relative amounts of each of the tracheary cell types.

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In this study, high-performance FAU (NaY type) zeolite membranes were successfully synthesized using small-sized seeds of 50 nm, and their gas separation performance was systematically evaluated. Employing nano-sized NaY seeds and an ultra-dilute reaction solution with a molar composition of 80 Na2O: 1Al2O3: 19 SiO2: 5000H2O, the effects of synthesis temperature, crystallization time, and porous support (α-Al2O3 or mullite) on the formation of FAU membranes were investigated. The results illustrated that further extending the crystallization time or increasing the synthesis temperature led to the formation of a NaP impurity phase on the FAU membrane layer. The most promising FAU membrane with a thickness of 2.7 µm was synthesized on an α-Al2O3 support at 368 K for 8 h and had good reproducibility. The H2 permeance of the membrane was as high as 5.34 × 10-7 mol/(m2 s Pa), and the H2/C3H8 and H2/i-C4H10 selectivities were 183 and 315, respectively. The C3H6/C3H8 selectivity of the membrane was as high as 46, with a remarkably high C3H6 permeance of 1.35 × 10-7 mol/(m2 s Pa). The excellent separation performance of the membrane is mainly attributed to the thin, defect-free membrane layer and the relatively wide pore size (0.74 nm).

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BLADE-ON-PETIOLE (BOP) genes are essential regulators of vegetative and reproductive development in land plants. First characterized in Arabidopsis thaliana (Arabidopsis), members of this clade function as transcriptional co-activators by recruiting TGACG-motif binding (TGA) basic leucine zipper (bZIP) transcription factors. Highly expressed at organ boundaries, these genes are also expressed in vascular tissue and contribute to lignin biosynthesis during secondary growth. How these genes function in trees, which undergo extensive secondary growth to produce wood, remains unclear. Here, we investigate the functional conservation of BOP orthologs in Populus trichocarpa (poplar), a widely-used model for tree development. Within the poplar genome, we identified two BOP-like genes, PtrBPL1 and PtrBPL2, with abundant transcripts in stems. To assess their functions, we used heterologous assays in Arabidopsis plants. The promoters of PtrBPL1 and PtrBPL2, fused with a ß-glucuronidase (GUS) reporter gene showed activity at organ boundaries and in secondary xylem and phloem. When introduced into Arabidopsis plants, PtrBPL1 and PtrBPL2 complemented leaf and flower patterning defects in bop1 bop2 mutants. Notably, Arabidopsis plants overexpressing PtrBPL1 and PtrBPL2 showed defects in stem elongation and the lignification of secondary tissues in the hypocotyl and stem. Finally, PtrBPL1 and PtrBPL2 formed complexes with TGA bZIP proteins in yeast. Collectively, our findings suggest that PtrBPL1 and PtrBPL2 are orthologs of Arabidopsis BOP1 and BOP2, potentially contributing to secondary growth regulation in poplar trees. This work provides a foundation for functional studies in trees.

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Metal-organic frameworks (MOFs) are promising electrocatalysts for clean energy conversion systems. However, developing MOF-based electrodes with high performance toward oxygen evolution reaction (OER) is still challenging. In this work, a series of MOF film electrodes derived from Ni-btz were prepared by employing the secondary growth strategy under solvothermal conditions. Fe and Co ions were also incorporated into the Ni-btz framework to produce a trimetallic coupling effect to obtain enhanced OER activity. The as-prepared FeCoNi-btz/NF exhibited not only good stability but also excellent OER performance under alkaline conditions. Furthermore, the possible intermediates including metal oxides and metal oxyhydroxides were confirmed by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).

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Evidence for secondary growth extends into the Early Devonian, 407 million years ago, raising questions about tempo and mode of origination of this key developmental feature. To address such questions, we analyze anatomy in the four oldest fossil plants with well-characterized woody tissues; one of these represents a new genus, described here formally. The new fossil is documented using the cellulose acetate peel technique and associated methods. We use the paradigm of structural fingerprints to identify developmental components of cambial growth based on fossil anatomy. We integrate developmental inferences within a theoretical framework of modular regulation of secondary growth. The fossils possess structural fingerprints consistent with four different combinations of regulatory mechanisms (modules) acting in cambial growth, representing four distinct modes of secondary growth. The different modes of secondary growth demonstrate that cambial growth is an assemblage of regulatory modules whose deployment followed a mosaic pattern across woody plants, which may represent ancestors of younger lineages that exhibit woody growth. The diverse modes of wood development occupy a wide morphospace in the anatomy of wood in the Early Devonian, suggesting that the origins of secondary growth and of its modular components pre-date this interval.

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