Palynological insights into Albuca virens (Hyacinthaceae) with ultrastructural evidence for taxonomic reevaluation

A palynological study of the Tulipa genus reveals distinct ultrastructural characters in Tulipa julia compared to the other examined species. Pollen micromorphology and ultrastructure of this species are determined by using Light Microscopy (LM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Pollen grains are monads, medium, and oblate-spheroidal. The exine ornamentation is rugulate-tuberculate. Also, ultrastructural observations show the presence of the endexine layer, the foot layer relatively thinner than the tectum, and a similar thickness between the ectexine and intine layers. Although, some pollen micromorphology characters align with the previous palynological research, the unique ultrastructural features such as the tectum/foot layer ratio (T/F) and presence of the endexine layer are determined in T. julia. These sporoderm data can be valuable for taxonomic classification at the subgenus Tulipa (T/F ratio and the number of intine layers) and section Tulipanum (presence of the endexine) levels.

In this research, pollen micromorphology and ultrastructure of eight species belonging to genera including Alrawia, Bellevalia, Fessia, Muscari, Othocallis, Prospero, Puschkinia, and Zagrosia were investigated by light microscopy, scanning electron microscopy, and transmission electron microscopy. The pollen size varied among the studied species. Othocallis monanthos and Muscari neglectum had the largest and smallest pollen grains, respectively. Based on the Polar axis/Equatorial axis (P/E) ratio, Bellevalia saviczii had peroblate pollen shape and the rest were oblate. Exine ornamentation on the equatorial surface, sulcus margin exine ornamentation, and intine ornamentation in the sulcus membrane region of the pollen grains varied among the selected species of all genera. The exine layer in all genera had semitectate tectum, simplicolumellate infratectum, and discontinuous foot layer. There was discontinuous endexine in M. neglectum, Prospero autumnale, and Zagrosia persica. Alrawia bellii, P. autumnale, and Puschkinia scilloides had three intine layers in the sulcus membrane region, O. monanthos had two, and the rest of the species had one. Also, in those species with three layers in the sulcus membrane region, the outer intine layer had many channels. A dendrogram of the palynological characters grouped them into three pollen types and six pollen subtypes. The pollen types verified the phylogenetic relationships among the studied genera, whereas the pollen subtypes partly supported these relationships.

Applying an immunocytochemical method, a localization of the protein Cry j I in the Cryptomeria japonica pollen, which is the major allergen responsible for Japanese cedar pollinosis, is investigated with the monoclonal and polyclonal antibodies produced from the protein. The protein that reacts to the polyclonal antibody localizes on the sexine, nexine, between nexine and intine layers, orbicles, cell wall of a generative cell, Golgi body and Golgi vesicles. The allergenic protein contained in the exine and orbicles of Japanese cedar pollen can diffuse or dissolve easily from there into the mucus covering of the eye and nose, causing a response in less than 1 min after exposure. Since the orbicles have a diameter of about 430 nm, they can pass easily through the pores of most protective masks to reach the sensitive tissues of the patient. The proteins react to the monoclonal antibodies (J1BO1 and J1BO7) and localize on the Golgi body, sexine, nexine and orbicles (but not between the nexine and intine layers), and on the generative cell wall. In the young pollen grain, numerous allergenic protein particles contained in the orbicles and sexine layer, but there is only a small amount of the protein between the nexine and intine layers, since the intine layer is not yet complete at this stage. More will be accumulated there during developmental maturation. The allergenic protein is also found on the tapetal materials remaining in the young anther. Since the materials forming the exine layer and orbicles come from tapetal tissue, it is assumed that some of the allergenic protein is produced in the tapetum and localized in the orbicles and pollen wall during maturation, and that the rest of the allergenic protein is produced in the Golgi body in the mature pollen grain.

Congenital Hereditary Endothelial Dystrophy Associated with Glaucoma

Direct observations of anodic barrier layer oxide, by transmission electron microscopy, provide further evidence for the duplex film structuring suggested earlier, based on infrared data. Anodic films were prepared with a boric acid electrolyte maintained at 60°C and two film layers were observed: the uppermost layer being extremely thin. Only the layer lying next to the metal (primary phase barrier layer) showed a thickness relationship with respect to forming voltage: 14.8 Aå/v. The thickness of the uppermost layer (secondary phase barrier layer) was on the order of 200Aå and was essentially independent of forming voltage. With the boric acid electrolyte employed at 90° C, a pronounced increase was found in the thickness of the uppermost layer. The thickness of the layer next to the metal surface remained consistent with the ∼14 Aå/v relationship. Infrared, coating weight, effluent gas detection, and impedance data were also obtained for these coatings and correlated with the data obtained by transmission electron microscopy.

Pollen micromorphology and ultrastructure of Colchicum kotschyi and Colchicum robustum were examined by Light Microscopy (LM), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The observations showed that all quantitative characters of pollen micromorphology varied in the studied taxa. Although, pollen grains in both species were oblate. Two pollen types, two major exine ornamentations in the equatorial surface of pollen grain with two kinds of pore intine ornamentation were seen during this research. Regarding sporoderm data, the thickness of the pollen wall layer, state of the endexine layer, and number of intine layers of C. kotschyi were different from C. robustum. Sporoderm characters strongly supported the unique position of C. robustum resulting from previous palynological research.

Pollen plays important roles in the life cycle of angiosperms plants. It acts as not only a biological protector of male sperms but also a communicator between the male and the female reproductive organs, facilitating pollination and fertilization. Pollen is produced within the anther, and covered by the specialized outer envelope, pollen wall. Although the morphology of pollen varies among different plant species, the pollen wall is mainly comprised of three layers: the pollen coat, the outer exine layer, and the inner intine layer. Except the intine layer, the other two layers are basically of lipidic nature. Particularly, the outer pollen wall layer, the exine, is a highly resistant biopolymer of phenylpropanoid and lipidic monomers covalently coupled by ether and ester linkages. The precise molecular mechanisms underlying pollen coat formation and exine patterning remain largely elusive. Herein, we summarize the current genetic, phenotypic and biochemical studies regarding to the pollen exine development and underlying molecular regulatory mechanisms mainly obtained from monocot rice (Oryza sativa) and dicot Arabidopsis thaliana, aiming to extend our understandings of plant male reproductive biology. Genes, enzymes/proteins and regulatory factors that appear to play conserved and diversified roles in lipid biosynthesis, transportation and modification during pollen exine formation, were highlighted.

3D morphology of photoactive layers of polymer solar cells

Open AccessCCS ChemistryRESEARCH ARTICLE14 Jul 2022Enormous Promotion of Photocatalytic Activity through the Use of Near-Single Layer Covalent Organic Frameworks Xiaomin Ren†, Chunzhi Li†, Wanchao Kang†, He Li, Na Ta, Sheng Ye, Linyan Hu, Xiuli Wang, Can Li and Qihua Yang Xiaomin Ren† State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 University of Chinese Academy of Sciences, Beijing 100049 , Chunzhi Li† State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 University of Chinese Academy of Sciences, Beijing 100049 , Wanchao Kang† State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000 , He Li State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 , Na Ta State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 , Sheng Ye State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 , Linyan Hu State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 , Xiuli Wang *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 , Can Li *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 University of Chinese Academy of Sciences, Beijing 100049 and Qihua Yang *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 https://doi.org/10.31635/ccschem.021.202101090 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Enhancing the charge separation efficiency is highly effective strategy in improving the photocatalytic activity of covalent organic frameworks (COFs) which have the problems of low conductivity and difficult dissociation of excitons. In this work, we report the sevenfold increase in apparent quantum efficiency resulting from the use of a near-single layer COF (SLCOF) in photocatalytic hydrogen evolution compared with bulk COF. Detected by transient absorption spectroscopy characterization, 100% of photogenerated long-lived electrons in the near-SLCOF can be extracted and participate in the photocatalytic process. However, the electron extraction efficiency declined to only about 11% when the COFs were increased to eight layers, implying the difficulty of charge migration among COFs interlayers. The near-SLCOF was prepared by deposition of self-exfoliated COFs colloids on SiO2, driven by their strong affinity. This work not only sheds light on the significant influence of COF layer thickness on the charge separation efficiency but also provides a new route to prepare and stabilize COF layers for practical applications. Download figure Download PowerPoint Introduction Photocatalytic water splitting to produce hydrogen is a desirable approach to sustainably store intermittent solar energy. Two-dimensional (2D) covalent organic frameworks (COFs) have emerged as a novel type of photocatalyst due to their unique optoelectronic properties and π-conjugated skeleton which can be designed at the molecular level.1–10 Visible-light-responsive 2D COFs for example, diacetylene functionalized COFs,11 azine COF,12 sp2-carbon-linked triazine-cored COFs,13–15 thiazolo thiazole-linked COFs,16 hydrazone-based COFs,17 and sulfone-containing COFs18 have been synthesized and used for visible-light-driven H2 production. However, most COFs show mediocre activity in photocatalytic hydrogen evolution (PHE) compared with traditional inorganic semiconductors, which is mainly related to the difficulty in dissociation of excitons and the rapid recombination of photogenerated electrons and holes during the photocatalytic process.19 Several strategies have been developed to improve the charge separation efficiency of COFs, for example, incorporating donor–acceptor (D–A) moieties20,21 or halogen atoms in COFs,22,23 constructing novel π-conjugated building blocks,24 and generating junctions with other semiconductors.25 In addition to the above strategies, reducing the particle size of COFs to nanometer scale is a more facile method to improve the charge separation efficiency due to the possibility of the charge carrier recombination being reduced in the short diffusion distance.26 Therefore, the single-layer COFs (SLCOFs) offering the minimum diffusion distance for charge carriers should be the perfect candidate for photocatalysis. Although SLCOFs can be successfully prepared on single-crystal surfaces and solid–vapor–liquid interfaces,27–30 such materials are unsuitable for application in photocatalysis due to the difficulty in preventing the stacking of freestanding SLCOFs and the scale-up synthesis. Recently, partitioning the interlayer space of COFs and the acid-aided exfoliation method have been used for the synthesis of monolayer COFs, but the yields of SLCOFs by these approaches have not been high. The facile synthesis and stabilization of SLCOFs still remains a challenge.31,32 Herein, we report the preparation of a near-SLCOF by self-exfoliating of COF colloids in the presence of SiO2 nanospheres and other supports which have strong affinity for COF colloids. COFs with near-single to multiple layers were successfully deposited on SiO2 nanospheres under fine control, providing an ideal model to study the relationship between layer thickness and charge separation efficiency. It was found that almost all the photogenerated long-lived electrons in the near-SLCOF could be used for H2 production, and this value decreased sharply with the increase of COF , which elucidated the remarkable improvement in charge separation efficiency by decreasing the diffusion distance. Experimental Methods Synthesis of TP-TTA colloids The synthesis of 1,3,5-triformylphloroglucinol (TP)-4,4′,4″-(1,3,5-triazine-2,4,6-triyl)trianiline (TTA) COF colloids was similar to the method in the literature with a slight modification.33 In a typical process, 29.4 mg (0.14 mmol) of TP was dissolved in 0.5 mL of dimethyl sulfoxide (DMSO). The solution was added dropwise to a flask containing 58 mL of 0.05 M hexadecyl trimethyl ammonium bromide (CTAB) aqueous solution. After ultrasonication, 1.8 mL of 0.05 M sodium dodecyl sulfate (SDS) aqueous solution was added to form solution A. Separately, 49.6 mg (0.14 mmol) of TTA was dissolved in 1 mL of DMSO. The solution was added dropwise to a flask containing 58 mL of 0.05 M CTAB aqueous solution. After ultrasonication, 1.8 mL of 0.05 M SDS solution was added to form solution B. Finally, the solutions A and B were mixed, and 5.8 mL of acetic acid was added to the resultant solution. After reacting at 30 °C for 48 h, a completely transparent orange colloidal solution was formed. Synthesis of TP-TTA/SiO2-x In a typical process, the pH of the TP-TTA colloids solution was adjusted to 7 with NaOH (1 M), followed by the addition of the desired amounts of SiO2 colloid solution, which was diluted to 15 mg/mL with water. After stirring at room temperature for 24 h, the mixture was heated at 110 °C to evaporate the solvent to afford solid products. After thoroughly washing the mixture with ethanol five times and degassing at 120 °C for 12 h under vacuum, TP-TTA/SiO2-x was obtained. TP-TTA/MOx (MOx = TiO2, WO3, Nb2O5, ZrO2) and TP-TTA/CdS were synthesized in a similar procedure to TP-TTA/SiO2-8 with the exception that CdS/MOx supports were used instead of SiO2 colloid solution (for details, see Supporting Information). PHE A flask charged with 50 mg of photocatalyst and 30 mL of 0.1 M ascorbic acid water solution was degassed by three freeze–pump–thaw cycles. An aqueous solution of H2PtCl6 (3 wt % of COF content) was injected into the flask under inert gas. The reaction mixture was illuminated with a 300 W Xenon lamp (PLS-SXE300/300 UV, Perfect Light, China) with a cutoff filter of 420 nm. The temperature of the reaction solution was maintained at 25 °C. Gas samples were taken with a gas-tight syringe (Hamilton 1700) and run on an Agilent 6890 gas chromatograph with a thermal conductivity detector (TCD) referencing against standard gas with a known concentration of hydrogen. Hydrogen dissolved in the reaction mixture was not measured, and the pressure increase generated by the evolved hydrogen was neglected in the calculations. Results and Discussion The TP-TTA colloids confined in CTAB/SDS micelle were prepared according to the method in the literature33 using TP and TTA as monomers. The size of TP-TTA colloids is ∼28 nm as measured by the dynamic light scattering (DLS) method ( Supporting Information Figure S1 and for synthesis details, see Supporting Information). TP-TTA/SiO2-x (x denotes the layer number of TP-TTA) samples with different COF layers were prepared by dispersing commercial SiO2 nanospheres (particle size ∼26 nm) in TP-TTA colloid solution (Scheme 1). The layer number of TP-TTA on SiO2 was facilely controlled by varying the mass ratio of TP-TTA colloids and SiO2 nanospheres in the initial mixture. Scheme 1 | The illustration of preparation of TP-TTA/SiO2-x (x denotes the layer number of TP-TTA) by self-exfoliating of TP-TTA colloids. Download figure Download PowerPoint The TP-TTA content of TP-TTA/SiO2-1, TP-TTA/SiO2-5, and TP-TTA/SiO2-8 was, respectively, 1.0, 4.1, and 7.1 wt % determined by 1H NMR analysis of digested TP-TTA/SiO2-x (for details, see Supporting Information and Supporting Information Figure S2). The Fourier transform infrared (FT-IR) spectra of TP-TTA/SiO2-x clearly showed the vibrations assigned to C=C, C=O and the aromatic ring respectively at 1578, 1625, and 1598 cm−1, together with the vibrations from triazine ring at 1370 and 1510 cm−1, implying the existence of TP-TTA with β-ketoenamine linkage34–36 (Figure 1a and Supporting Information Figures S3a, S3b, S3e, and S3f). No obvious absorption peaks attributed to CTAB and SDS were observed in the FT-IR spectrum of TP-TTA/SiO2-8, indicating no or a lesser amount of residue. The 13C cross-polarization total suppression of sidebands (CP-TOSS) NMR spectrum of TP-TTA/SiO2-8 exhibited characteristic chemical shifts at 183 and 106 ppm representing –C=O of the keto form and –C=C of the aryl ring. The chemical shifts at ∼170 and ∼131 ppm were assigned to the C atoms of triazine units and the C atoms directly connected to the triazine units37 (Figure 1b). The signals in the range of 14–35 ppm assigned to alkane carbons of CTAB and SDS appeared in the NMR spectrum of TP-TTA/SiO2-8. Thermogravimetric analysis (TGA) showed ∼6.9±1 wt % of organic content in TP-TTA/SiO2-8 ( Supporting Information Figure S4), in agreement with the content of TP-TTA determined by 1H NMR, showing the low amount of surfactant in the sample. The relatively stronger signals of the surfactant were mainly due to the cross-polarization experiment. For the 13C atom with a 1H atom directly connected to it, stronger coupling between 1H and 13C enhanced the intensity of the signal because the magnetization transfer from 1H to 13C by simultaneously applying matching radiofrequency fields to both spins, according to the Hartmann–Hahn condition. The combination of FT-IR spectra and 13C CP-TOSS NMR characterization confirmed the existence of TP-TTA on SiO2. Figure 1 | (a) FT-IR and (b) 13C CP-TOSS NMR spectra of TP-TTA/SiO2-8, (c) UV–vis spectra of TP-TTA/SiO2 samples dispersed in water (A1 and A8 refer to the absorbance at 450 nm). Download figure Download PowerPoint The uniformly dispersed nanospheres with smooth surfaces identical to the parent SiO2 were observed in the transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images of TP-TTA/SiO2-x samples, and the absence of other polymer phases implied that TP-TTA was mostly deposited on the surface of SiO2 (Figure 2a and Supporting Information Figures S5a–S5d). The scanning TEM (STEM) images and elemental mappings of TP-TTA/SiO2-x clearly showed a uniform distribution of C elements on the surface, suggesting that TP-TTA evenly wrapped on SiO2 nanoparticles (NPs) (Figures 2b–2d). The energy-dispersive system (EDS) mapping of nitrogen species was collected simultaneously. Due to the intrinsic low N content in the as-prepared sample, the signal-to-noise ratio of N elemental mapping was too low to generate an image with high quality. Although we had tried to obtain a better result by increasing both the dose rate and the integration time, the serious beam damage and the carbon contamination during lengthy collection times significantly degraded the spatial resolution of EDS mapping. The thickness of TP-TTA on the SiO2 increased from TP-TTA/SiO2-1 to TP-TTA/SiO2-8 which was evidenced by the increased intensity of the carbon signal. The TP-TTA layer thickness of TP-TTA/SiO2-8 was approximately 3.0 nm measured from the STEM elemental mapping. It is difficult to get the accurate thickness of the TP-TTA layer for TP-TTA/SiO2-1 and TP-TTA/SiO2-5 due to the weak signals of C elemental mapping. The thickness of the TP-TTA layer was calculated to be 0.46 and 1.81 nm, respectively, for TP-TTA/SiO2-1 and TP-TTA/SiO2-5 based on the density formula (for details, see Supporting Information). With the distance between adjacent layers of TP-TTA COFs approximately 0.37 nm by Vienna Ab-initio Simulation Package (VASP) (as shown in Supporting Information Table S1), the TP-TTA layer numbers for TP-TTA/SiO2-1, TP-TTA/SiO2-5, and TP-TTA/SiO2-8 were ∼1, ∼5, and ∼8, respectively. Figure 2 | (a) TEM image of TP-TTA/SiO2-8. STEM images and elemental mapping of (b) TP-TTA/SiO2-1, (c) TP-TTA/SiO2-5, (d) TP-TTA/SiO2-8, (e) TP-TTA/TiO2, and (f) TP-TTA/CdS. HRTEM images of (g) TP-TTA/TiO2 and (h) TP-TTA/CdS. Download figure Download PowerPoint The specific surface area of TP-TTA/SiO2-x was measured by Ar sorption at 87 K ( Supporting Information Table S2 and Figure S6) and calculated with the Brunauer–Emmett–Teller (BET) method. The specific surface area of TP-TTA/SiO2-1 was almost identical to the parent SiO2. The TP-TTA/SiO2-5 and TP-TTA/SiO2-8 showed higher BET surface area than SiO2. No micropore assigned to TP-TTA COF at 0.6 and 0.9 nm could be observed in the pore size distribution curve of TP-TTA/SiO2-1, implying a monolayer structure. TP-TTA/SiO2-5 and TP-TTA/SiO2-8 afforded the micropore from TP-TTA COF, further confirming the presence of multilayer TP-TTA ( Supporting Information Figure S6). The powder X-ray diffraction (PXRD) patterns of TP-TTA/SiO2-8 and TP-TTA displayed intense peaks at 5.7°, 9.2°, and 14.9°, respectively, attributed to the 100, 110, and 210 reflections, implying that the multilayer TP-TTA on SiO2 has a crystalline structure ( Supporting Information Figure S7). Two kinds of stacking arrangements (eclipsed AA and staggered AB) were applied to generate the hexagonal unit cells for TP-TTA COF. After geometrical optimization of the models, the experimental PXRD patterns of the TP-TTA COFs and TP-TTA/SiO2-8 were more likely to match the simulated diffraction patterns of the AA-stacking models, in good agreement with reports in the literature.38 The deposition of TP-TTA with varied thickness on SiO2 suggested that the exfoliation of TP-TTA colloids occurred during the deposition process. CdS, TiO2, WO3, Nb2O5, and ZrO2 were also used as supports for the deposition of TP-TTA. The high-resolution TEM (HRTEM) images showed a uniform coating of TP-TTA layers on the surface of CdS/TiO2 with a clear boundary between TP-TTA layers and TiO2/CdS, which was further confirmed by the STEM images and elemental mapping (Figures 2e–2h). The thickness of TP-TTA layers was 3.6 and 2.6 nm, respectively, for TP-TTA/TiO2 and TP-TTA/CdS, indicating the exfoliating deposition behavior of COF layers on the above solid supports. No polymer phase could be observed in the SEM image of TP-TTA/TiO2 and TP-TTA/CdS ( Supporting Information Figures S5e–S5h). The appearance of the characteristic vibrations of TP-TTA in the FT-IR spectra of TP-TTA/CdS and TP-TTA/TiO2 confirmed the formation of hybrid materials ( Supporting Information Figures S3c and S3d). Unfortunately, the SEM images and the corresponding EDS mapping results showed the coexistence of COF aggregates and metal oxide NPs when using WO3, Nb2O5, and ZrO2 as supports, implying that TP-TTA colloids can hardly be exfoliated on the surface of WO3, Nb2O5, and ZrO2 ( Supporting Information Figure S8). The interaction between adjacent layers of COFs involves the noncovalent van der Waals force.39–41 The size of TP-TTA COF colloids is ∼28 nm due to the surrounding compact surfactant layer preventing further growth and flocculation.33 Density functional theory (DFT) calculation showed that the exfoliation energy of TP-TTA COF (AA stacking) is directly related to the layer thickness ( Supporting Information Figure S9). The more layers, the more difficult it is to exfoliate. Consequently, the TP-TTA colloids with much smaller layer number than bulk TP-TTA COFs had weak interlayer strength which facilitated the stripping of TP-TTA layers. Furthermore, TP-TTA colloids synthesized at 30 °C have lower degrees of polymerization than COFs synthesized by the traditional solvothermal method, which further impaired the interaction strength among TP-TTA layers. When the interaction strength between the solid supports and TP-TTA COF colloids is stronger than the π−π staking (AA) strength between the TP-TTA layers, the exfoliation of TP-TTA COF colloids may occur. This is reasonable considering that the 2D imine-linked COF powders can be exfoliated in the presence of acid by temporarily weakening their interlayer stacking through electrostatic repulsion.42 To decrease the surface tension, the TP-TTA single layer tends to deposit on solid supports driven by the H-bonds or other interactions. In the presence of higher amounts of TP-TTA colloids in the synthesis mixture, multilayer TP-TTA was formed on the supports, possibly by the restacking of the single layer due to π–π interactions driven by the high temperature used for the solvent evaporation. Another important parameter for the exfoliating TP-TTA colloids on supports is the pH value of the colloid solution. By mixing SiO2 and TP-TTA colloids (adjusted to pH of 7), the positively charged TP-TTA colloids (zeta potential value of 60 mV, Supporting Information Figure S10) interacted with negatively charged SiO2 nanospheres (isoelectric point of 1.5–3.5) through electrostatic interactions to destroy the colloids. Thus, the TP-TTA was released from the micelles and delaminated into a single-layer, driven by the strong interaction of SiO2 and TP-TTA colloids. The control experiment was performed by mixing SiO2 and TP-TTA colloids with pH adjusted to 1. The TEM image of the resultant material showed the coexistence of SiO2 nanospheres and irregularly shaped TP-TTA ( Supporting Information Figure S5i). At pH of 1, the surface of SiO2 is positively charged, which does not favor the contact with the positively charged TP-TTA colloids. The control experiment signifies the importance of surface electrostatic interactions in successful deposition of TP-TTA layers on SiO2. In comparison with previously reported methods,43 the self-exfoliation of COF colloids could precisely control the layer thickness, and the SiO2 support could prevent the stacking of COF layers during the practical application process. More importantly, this method is easy for the scale-up synthesis. The color changed gradually from light yellow to yellow brown when TP-TTA content increased ( Supporting Information Figure S11). The UV–vis spectra of TP-TTA/SiO2-x water suspension gradually showed red shifts of the absorption edge from 427 to 440 nm with increased layers (Figure 1c). This can be attributed to an increased conjugation length with layer thickness and/or the J-type aggregation with the chromophores between adjacent layers.44,45 The UV–vis reflectance of solid TP-TTA/SiO2-x showed a similar tendency ( Supporting Information Figure S11). Calculated by Tauc plots,46,47 the optical band gaps of TP-TTA/SiO2-x varied from 2.28 to 2.41 eV, showing a slight increase of band gap with the decrease of the TP-TTA layer ( Supporting Information Figure S11). Mott–Schottky tests were performed to determine the band minimum of the materials ( Supporting Information Figure The for TP-TTA COF and TP-TTA/SiO2-x was hydrogen which is than the potential ( Supporting Information Figure The above results the for PHE by TP-TTA/SiO2-x and TP-TTA COFs under The PHE activity of TP-TTA/SiO2-x and corresponding bulk TP-TTA COFs ( Supporting Information Figures and was in a H2 evolution reaction under light 420 nm) with ascorbic acid as a and NPs from H2PtCl6 as a (for details, see Supporting Information). showed no H2 evolution occurred light and with a that the PHE reaction only under light and in the presence of a shown in Figure the of H2 increased with the TP-TTA COF and TP-TTA/SiO2 The H2 evolution rate was relatively during the 0.5 h, possibly due to the of which is a for TP-TTA/SiO2-1 H2 in h, much higher than the content in the showing that the H2 is not from the of the The experiment confirmed that the H2 from water ( Supporting Information Figure The H2 evolution rate was calculated 1 h reaction to the influence of the The H2 evolution rate decreased from to when increasing the layer numbers from 1 to (Figure TP-TTA/SiO2 samples were more than TP-TTA COF with the H2 evolution rate of the samples had much lower content of TP-TTA. Therefore, it is reasonable to that the more precisely the thickness, of TP-TTA significantly photocatalytic activity by the diffusion distance of charge The H2 evolution rate of TP-TTA/SiO2-1 was as high as this remarkable the for reported ( Supporting Information Table Figure | (a) PHE as a of reaction with 50 mg TP-TTA/SiO2-x and TP-TTA COFs under nm, in the presence of 30 mL 0.1 M ascorbic acid and wt % (b) The of layer numbers of TP-TTA with PHE rate and (c) of H2 (d) of H2 evolution Download figure Download PowerPoint The apparent quantum efficiency of TP-TTA/SiO2-1 was measured using a 300 W Xenon lamp with a and nm filter (Figure for details, see Supporting Information). The of at different was in good agreement with optical absorption The at 440 nm for TP-TTA/SiO2-1 which is times higher than TP-TTA COF with of With increased layer thickness, the decreased (Figure In a PHE no activity was observed h using TP-TTA/SiO2-1 as the model photocatalyst (Figure The TP-TTA/SiO2-1 had similar and optical absorption properties as the the high of TP-TTA/SiO2-1 during the photocatalysis ( Supporting Information Figure Figure | absorption of (a) TP-TTA/SiO2-1 and (b) TP-TTA/SiO2-8 in water in 0.1 M ascorbic acid and in 0.1 M ascorbic acid with at 450 nm, at nm). (c) for TP-TTA/SiO2-1 and TP-TTA/SiO2-8 in the presence of ascorbic (d) The electron extraction efficiency of TP-TTA/SiO2-1 and TP-TTA/SiO2-8. Download figure Download PowerPoint The of TP-TTA/SiO2 samples was almost the suggesting that the high PHE activity of TP-TTA/SiO2-1 was not due to the different for ( Supporting Information Figure to the surface of COFs has a influence on the PHE The water contact of TP-TTA/SiO2-x was measured, and the results showed that TP-TTA/SiO2 samples and TP-TTA COFs had a similar water contact of ( Supporting Information Figure implying that the surface is not for the in PHE spectroscopy and of TP-TTA/SiO2-x samples were performed and compared with TP-TTA shown in Supporting Information Figure the of TP-TTA/SiO2-x increased with the increase of the layer number of suggesting that TP-TTA could improve charge The of TP-TTA/SiO2 samples also increased with the decrease of the number of TP-TTA layers, indicating that the transmission distance was for the separation of photogenerated charge carriers ( Supporting Information Figure a the PHE rate of TP-TTA/SiO2-1 was enhanced to TP-TTA COF. To further the charge separation efficiency of TP-TTA/SiO2 samples, transient absorption spectra of the water of TP-TTA/SiO2-1 and TP-TTA/SiO2-8 were In the presence of the the signal at nm was observed for both samples, and the was increased at the scale in the presence of the (Figures and Supporting Information Figure confirming that in such long-lived signal in is from electrons and the The initial could be used to the number of electrons due to the between the electron numbers and the intensity of the signal. The initial increased from for TP-TTA/SiO2-1 to for TP-TTA/SiO2-8 in ascorbic The ratio = of the initial of TP-TTA/SiO2-8 and TP-TTA/SiO2-1 was in good with the ratio = of their absorbance at 450 nm under the intensity (Figure 1c). This good agreement that all the light by TP-TTA/SiO2-x generate long-lived electrons in the presence of ascorbic their similar dissociation TP-TTA/SiO2-1 and TP-TTA/SiO2-8 have of electrons the when the to of the initial of and respectively (Figure The behavior of electron extraction from TP-TTA/SiO2 samples to was by the was (Figure and Supporting Information Figure In the presence of the signal reduced for TP-TTA/SiO2 samples, indicating the migration of electrons to to participate in the For TP-TTA/SiO2-1, the signal to a weak absorption signal by the of indicating that the corresponding to the weak absorption participate in the The electron

We isolated a pollen-preferential gene, RICE IMMATURE POLLEN 1 (RIP1), from a T-DNA insertional population of japonica rice that was trapped by a promoterless beta-glucuronidase (GUS) gene. Semi-quantitative reverse transcription-PCR (RT-PCR) analyses confirmed that the RIP1 transcript was abundant at the late stages of pollen development. Transgenic plants carrying a T-DNA insertion in the RIP1 gene displayed the phenotype of segregation distortion of the mutated rip1 gene. Moreover, rip1/rip1 homozygous progeny were not present. Reciprocal crosses between Rip1/rip1 heterozygous plants and the wild type showed that the rip1 allele could not be transmitted through the male. Microscopic analysis demonstrated that development in the rip1 pollen was delayed, starting at the early vacuolated stage. Close examination of that pollen by transmission electron microscopy also showed delayed formation of starch granules and the intine layer. In addition, development of the mitochondria, Golgi apparatus, lipid bodies, plastids and endoplasmic reticulum was deferred in the mutant pollen. Under in vitro conditions, germination of this mutant pollen did not occur, whereas the rate for wild-type pollen was >90%. These results indicate that RIP1 is necessary for pollen maturation and germination. This gene encodes a protein that shares significant homology with a group of proteins containing five WD40 repeat sequences. The green fluorescent protein (GFP)-RIP1 fusion protein is localized to the nucleus. Therefore, RIP1 is probably a nuclear protein that may form a functional complex with other proteins and carry out essential cellular and developmental roles during the late stage of pollen formation.

Nanostructured polymers and ultra‐thin polymer layers are used more and more in technical applications like nanotechnology and microelectronics. Therefore, it is really important to understand the size‐scale dependent properties as bulk polymers become thinner and more two‐dimensional. Here the morphology as well as the macroscopic and the microscopic deformation behaviour of multilayered films of polypropylene (PP) and polystyrene (PS) have been investigated. For investigation different microscopic techniques and tensile testing were used. The films were prepared by multilayer coextrusion, whereas the composition of PP and PS and the film thickness – and therefore the thickness of each layer – varied. The thinnest calculated thickness of a single layer was about 5 nm. It is shown that the PP/PS films consist usually of homogeneous layers with only few defects. As the composition of PP/PS deviates strongly from 50/50 or the films get thinner the number of defects increases and the layered system turns to irregular lamellar system. In macroscopic tensile tests the small PS layers affect the elongation at break enormously: Most of the samples are brittle. For the films with a composition of PP/PS 90/10 and the film PP/PS 70/30 with a film thickness of 25 µm an elongation at break of 66% and higher could be reached. Transmission electron microscopy on these samples shows that the layers are characterized by plastic yielding in local deformation zones.

Nine species from genera including Aloe, Asphodelus, Eremurus, and Hemerocallis (from subfamilies Asphodeloideae and Hemerocallidoideae) were examined by LM (Light Microscopy) and SEM (Scanning Electron Microscopy). Moreover, two species from Aloe and Eremurus were selected (Aloe vera and Eremurus spectabilis) and examined by TEM (Transmission Electron Microscopy). Our results showed that some qualitative (exine ornamentation from central and distal regions of the pollen grains and sulcus margin exine ornamentation) and all quantitative characteristics were varied. Dendrogram of the palynological characteristics constructed three pollen types (type 1 or Eremurus-Aloe type, type 2 or Asphodelus type, and type 3 or Hemerocallis type) that partly supported the genera level of the cladogram resulted from recent phylogenetical research and taxonomical issues. Also, the situation of subgenera from Eremurus was heterogenous in the palynological dendrogram. The studied species of Aloe and Eremurus were placed in type 1. The ultrastructure data, such as sporoderm thickness and number of intine layers in the sulcus margin region provided a better resolution for their differentiation from two selected species of these genera.

Formation pattern and regulatory mechanisms of pollen wall in Arabidopsis

Pollen morphology, sculpturing, and wall ultrastructure of the five species in the monocot family Philydraceae were investigated in order to assess phylogenetic relationships. All members of the Philydraceae have monosulcate, heteropolar pollen grains with a tectatecolumellate exine having distinctive lamellae inner to the foot-layer. Histochemical tests of Philydrum lanuginosum indicate an ektexinous exine composition. The aperture wall of all members of the family consists of a thick, 2-layered intine with exine absent or composed of scattered deposits. The inner intine layer is infused with numerous vesicular or channellike structures. Histochemical tests of Philydrum lanuginosum suggest that the outer intine layer is primarily cellulosic and the inner intine layer is pectic-rich, a trend opposite from that noted in pollen of other monocot taxa. Palynological similarities between the Philydraceae and related families, including monosulcate apertures and a tectate-columellate exine, are hypothe...

In the mature microspore ofSecale cereale, a set of wall ingrowths deposited as the first (outer) intine layer between exine and the microspore plasma membrane, are revealed by electron microscopy. The wall ingrowths form a girdle in the vicinity of the apertural region at the external pole of microspore which is in contact with the tapetum, so the microspore can be considered as a transfer cell which is polarized. After microspore division the second (inner) intine layer is deposited by the vegetative cell and forms a labyrinth of branched wall ingrowths. As a result, the periphery of a vegetative cell is also irregular and appears as very thin plasmatubules or evaginations delimited by plasma membrane and penetrating the pollen wall.