Association among starch storage, metabolism, related genes and growth of Moso bamboo (Phyllostachys heterocycla) shoots.

BACKGROUND: Both underground rhizomes/buds and above-ground Moso bamboo (Phyllostachys heterocycla) shoots/culms/branches are connected together into a close inter-connecting system in which nutrients are transported and shared among each organ. However, the starch storage and utilization mechanisms during bamboo shoot growth remain unclear. This study aimed to reveal in which organs starch was stored, how carbohydrates were transformed among each organ, and how the expression of key genes was regulated during bamboo shoot growth and developmental stages which should lay a foundation for developing new theoretical techniques for bamboo cultivation. RESULTS: Based on changes of the NSC content, starch metabolism-related enzyme activity and gene expression from S0 to S3, we observed that starch grains were mainly elliptical in shape and proliferated through budding and constriction. Content of both soluble sugar and starch in bamboo shoot peaked at S0, in which the former decreased gradually, and the latter initially decreased and then increased as shoots grew. Starch synthesis-related enzymes (AGPase, GBSS and SBE) and starch hydrolase (α-amylase and ß-amylase) activities exhibited the same dynamic change patterns as those of the starch content. From S0 to S3, the activity of starch synthesis-related enzyme and starch amylase in bamboo rhizome was significantly higher than that in bamboo shoot, while the NSC content in rhizomes was obviously lower than that in bamboo shoots. It was revealed by the comparative transcriptome analysis that the expression of starch synthesis-related enzyme-encoding genes were increased at S0, but reduced thereafter, with almost the same dynamic change tendency as the starch content and metabolism-related enzymes, especially during S0 and S1. It was revealed by the gene interaction analysis that AGPase and SBE were core genes for the starch and sucrose metabolism pathway. CONCLUSIONS: Bamboo shoots were the main organ in which starch was stored, while bamboo rhizome should be mainly functioned as a carbohydrate transportation channel and the second carbohydrate sink. Starch metabolism-related genes were expressed at the transcriptional level during underground growth, but at the post-transcriptional level during above-ground growth. It may be possible to enhance edible bamboo shoot quality for an alternative starch source through genetic engineering.

Phragmites australis (Reed) as an Efficient, Eco-Friendly Adsorbent for Brackish Water Pre-Treatment in Reverse Osmosis: A Kinetic Study.

A cost-effective adsorbent was prepared by carbonization of pre-treated Phragmites australis reed at 500 °C. Phragmites australis was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface analyses. XRD of the as-prepared adsorbent exhibited a partially crystalline structure with a specific surface area of 211.6 m2/g and an average pore diameter of 4.2 nm. The biosorption potential of novel biosorbent Phragmites australis reed was investigated with a batch scale and continuous flow study. The study was conducted at different constraints to obtain optimum pH conditions, adsorbent dose, contact time, agitation speed, and initial TDS concentration. In order to analyze the properties of the procedure and determine the amount of sodium removal, Langmuir, Freundlich, and Dubinin-Radushkevich isotherms were tested. The optimal values of contact time, pH, and adsorbent dose were found to be 150 min, 4, and 10 g/L, respectively, with an agitation speed of 300 rpm at room temperature (27 °C). The three tested isotherms show that the adsorption of Na+ onto the prepared adsorbent is a hybrid process from physi- and chemisorption. For industrial application, the adsorbent was tested using the adsorbent column technique. Pseudo-first-order, pseudo-second-order, and diffusion models were connected, and it was discovered that the information fit best to the pseudo-second-arrange active model. According to the intraparticle diffusion model, the mechanism goes through four stages before reaching equilibrium. The periodicity test shows that the adsorption ability of Phragmites australis can be recovered by washing with 0.1 M HCl.

Sustainable Drying and Torrefaction Processes of Miscanthus for Use as a Pelletized Solid Biofuel and Biocarbon-Carrier for Fertilizers.

Miscanthus is resistant to dry, frosty winters in Poland and most European Union countries. Miscanthus gives higher yields compared to native species. Farmers can produce Miscanthus pellets after drying it for their own heating purposes. From the third year, the most efficient plant development begins, resulting in a yield of 25-30 tons of dry matter from an area of 1 hectare. Laboratory scale tests were carried out on the processes of drying, compacting, and torrefaction of this biomass type. The analysis of the drying process was conducted at three temperature levels of the drying agent (60, 100, and 140 °C). Compaction on a hydraulic press was carried out in the pressure range characteristic of a pressure agglomeration (130.8-457.8 MPa) at different moisture contents of the raw material (0.5% and 10%). The main interest in this part was to assess the influence of drying temperature, moisture content, and compaction pressure on the specific densities (DE) and the mechanical durability of the pellets (DU). In the next step, laboratory analyses of the torrefaction process were carried out, initially using the Thermogravimetric Analysis TGA and Differential Scaning Calorimeter DSC techniques (to assess activation energy (EA)), followed by a flow reactor operating at five temperature levels (225, 250, 275, 300, and 525 °C). A SEM analysis of Miscanthus after torrefaction processes at three different temperatures was performed. Both the parameters of biochar (proximate and ultimate analysis) and the quality of the torgas (volatile organic content (VOC)) were analyzed. The results show that both drying temperature and moisture level will affect the quality of the pellets. Analysis of the torrefaction process shows clearly that the optimum process temperature would be around 300-340 °C from a mass loss ratio and economical perspective.

Coleataenia prionitis, a C4-like species in the Poaceae.

C4-like plants represent the penultimate stage of evolution from C3 to C4 plants. Although Coleataenia prionitis (formerly Panicum prionitis) has been described as a C4 plant, its leaf anatomy and gas exchange traits suggest that it may be a C4-like plant. Here, we reexamined the leaf structure and biochemical and physiological traits of photosynthesis in this grass. The large vascular bundles were surrounded by two layers of bundle sheath (BS): a colorless outer BS and a chloroplast-rich inner BS. Small vascular bundles, which generally had a single BS layer with various vascular structures, also occurred throughout the mesophyll together with BS cells not associated with vascular tissue. The mesophyll cells did not show a radial arrangement typical of Kranz anatomy. These features suggest that the leaf anatomy of C. prionitis is on the evolutionary pathway to a complete C4 Kranz type. Phosphoenolpyruvate carboxylase (PEPC) and pyruvate, Pi dikinase occurred in the mesophyll and outer BS. Glycine decarboxylase was confined to the inner BS. Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) accumulated in the mesophyll and both BSs. C. prionitis had biochemical traits of NADP-malic enzyme type, whereas its gas exchange traits were close to those of C4-like intermediate plants rather than C4 plants. A gas exchange study with a PEPC inhibitor suggested that Rubisco in the mesophyll could fix atmospheric CO2. These data demonstrate that C. prionitis is not a true C4 plant but should be considered as a C4-like plant.

Sucrose phosphate synthase (SPS), sucrose synthase (SUS) and their products in the leaves of Miscanthus × giganteus and Zea mays at low temperature.

MAIN CONCLUSION: The changes in the expression of key sugar metabolism enzymes (SPS and SUS), sucrose content and arrangement of chloroplast starch may play a significant role in the cold response in M. giganteus and maize plants. To understand the mechanism of the chilling-response of two closely-related C4 plants, we investigated the changes in the expression of sucrose phosphate synthase (SPS) and sucrose synthase (SUS) as well as changes in their potential products: sucrose, cellulose and starch in the leaves of Miscanthus × giganteus and Zea mays. Low temperature (12-14 °C) increased SPS content in Miscanthus (MG) and chilling-sensitive maize line (Zm-S), but not in chilling-tolerant one (Zm-T). In Zm-S line, chilling also caused the higher intensity of labelling of SPS in the cytoplasm of mesophyll cells, as demonstrated by electron microscopy. SUS labelling was also increased by cold stress only in MG plants what was observed in the secondary wall between mesophyll and bundle sheath cells, as well as in the vacuoles of companion cells. Cold led to a marked increase in total starch grain area in the chloroplasts of Zm-S line. In turn, Fourier transform infrared spectroscopy (FTIR) showed a slight shift in the cellulose band position, which may indicate the formation of more compact cellulose arrangement in Zm-T maize line. In conclusion, this work presents new findings supporting diversified cold-response, not only between two C4 plant species but also within one species of maize.

Effect of Hygrothermal Treatment on the Porous Structure and Nanomechanics of Moso Bamboo.

Hygrothermal treatment is an environmentally friendly and efficient modification method. In this study, Moso bamboo was modified with hygrothermal treatments, and the results of nitrogen adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and nano indentation (NI) were then examined. Interestingly, the samples that underwent hygrothermal treatment at 180 °C and 117% RH (relative humidity) had the highest crystallinity (36.92%), which was 11.07% statistically larger than that of the control samples. Simultaneously, the total pore volume and average pore diameter (2.72 nm) dramatically decreased by 38.2% and 43.7%, respectively. The NI elasticity and hardness of the samples also reached the highest values under this condition; both increased by nearly 21% as compared with the control samples. Therefore, 180 °C is a favorable hygrothermal treatment temperature for Moso bamboo modification due to the porosity changes and the improvement of the nanomechanics of the cell walls.

Mapping thermal conductivity across bamboo cell walls with scanning thermal microscopy.

Scanning thermal microscopy is a powerful tool for investigating biological materials and structures like bamboo and its cell walls. Alongside nanoscale topographical information, the technique reveals local variations in thermal conductivity of this elegant natural material. We observe that at the tissue scale, fibre cells in the scattered vascular tissue would offer preferential pathways for heat transport due to their higher conductivities in both anatomical directions, in comparison to parenchymatic cells in ground tissue. In addition, the transverse orientation offers more resistance to heat flow. Furthermore, we observe each fibre cell to compose of up to ten layers, with alternating thick and thin lamellae in the secondary wall. Notably, we find the thin lamellae to have relatively lower conductivity than the thick lamellae in the fibre direction. This is due to the distinct orientation of cellulose microfibrils within the cell wall layers, and that cellulose microfibrils are highly anisotropic and have higher conductivity along their lengths. Microfibrils in the thick lamellae are oriented almost parallel to the fibre cell axis, while microfibrils in the thin lamellae are oriented almost perpendicular to the cell axis. Bamboo grasses have evolved to rapidly deposit this combination of thick and thin layers, like a polymer composite laminate or cross-laminated timber, for combination of axial and transverse stiffness and strength. However, this architecture is found to have interesting implications on thermal transport in bamboo, which is relevant for the application of engineered bamboo in buildings. We further conclude that scanning thermal microscopy may be a useful technique in plant science research, including for phenotyping studies.

Taxonomic significance of caryopsis in subfamily Panicoideae (Poaceae) using scanning electron microscopy and light microscopy.

In recent study, 13 taxa of subfamily Panicoideae were investigated for morphological characterization of caryopsis. Light microscope (LM) and scanning electron microscope (SEM) were utilized to study macro- and micro-morphological caryopsis features respectively. Caryopsis size in studied taxa was recorded as 1.5-10 mm long and 1-4 mm wide. Caryopsis color was brown, green, yellow, and whitish-brown. Caryopsis shape studied was obovate, elliptic, linear oblate, and round shallowly obtriangular. Hilum position is grooved and depressed. Caryopsis compression type was lateral and dorsiventral. Major variations among studied taxa were observed in terms of caryopsis surface pattern and epicuticular projection types. Six types of caryopsis surface pattern were observed viz. scabrate, rugose, striate, reticulate, papillate, and scabridulous. Structures such as silica cells, bulges, spines, prickles, granules, and bicellular microhair were studied as epicuticular projections. Major variations were observed among Cenchrus pennisetiformis and Cenchrus ciliaris as both has entirely two different types of surface patterns and epicuticular projections. Anticlinal wall thickness and pattern as well as periclinal wall texture and level were investigated. The present research work emphasized on caryopsis characterization of subfamily Panicoideae and it is recommended to establish phylogeny within subfamily Panicoideae and with other subfamilies of Poaceae.

Phylogenetic relationships within Parianinae (Poaceae: Bambusoideae: Olyreae) with emphasis on Eremitis: Evidence from nuclear and plastid DNA sequences, macromorphology, and pollen ectexine patterns.

Eremitis, Pariana, and Parianella are herbaceous bamboos (tribe Olyreae) included in the subtribe Parianinae, which is characterized by the presence of fimbriae at the apex of the leaf sheaths and exclusively spiciform synflorescences. We analyzed 43 samples of herbaceous and woody bamboos in order to infer relationships within the Parianinae, based on combined data from the nuclear ribosomal internal transcribed spacer (ITS) and plastid DNA (rpl32-trnL and trnD-trnT spacers). Bayesian inference, maximum likelihood, and maximum parsimony methods were applied, and macro- and micromorphological aspects were also analyzed, including the ectexine patterns of pollen grains. Parianinae is represented by three well-supported lineages in our analyses: (1) Parianella, endemic to southern Bahia, Brazil; (2) Pariana sensu stricto with a broad distribution in southern Central America and northern South America, especially in the Amazon region; and (3) Eremitis, endemic to the Brazilian Atlantic Forest, from the states of Pernambuco to Rio de Janeiro, including one species previously described as a member of Pariana. Our molecular phylogeny showed that Pariana, as historically circumscribed, is not monophyletic, by recovering Pariana sensu stricto as strongly supported and sister to Eremitis + Pariana multiflora, with Parianella sister to the Pariana-Eremitis clade. Morphological features of their synflorescences and differences in ectexine patterns characterize each lineage. Based on all these characters and the phylogenetic results, Pariana multiflora, endemic to the state of Espírito Santo, Brazil, is transferred to Eremitis.

3D printed structures for modeling the Young's modulus of bamboo parenchyma.

Bamboo is a sustainable, lightweight material that is widely used in structural applications. To fully develop micromechanical models for plants, such as bamboo, the mechanical properties of each individual type of tissue are needed. However, separating individual tissues and testing them mechanically is challenging. Here, we report an alternative approach in which micro X-ray computed tomography (µ-CT) is used to image moso bamboo (Phyllostachys pubescens). The acquired images, which correspond to the 3D structure of the parenchyma, are then transformed into physical, albeit larger scale, structures by 3D printing, and their mechanical properties are characterized. The normalized longitudinal Young's moduli of the fabricated structures depend on relative density raised to a power between 2 and 3, suggesting that elastic deformation of the parenchyma cellular structure involves considerable cell wall bending. The mechanical behavior of other biological tissues may also be elucidated using this approach. STATEMENT OF SIGNIFICANCE: Bamboo is a lightweight, sustainable engineering material widely used in structural applications. By combining micro X-ray computed tomography and 3D printing, we have produced bamboo parenchyma mimics and characterized their stiffness. Using this approach, we gained insight into bamboo parenchyma tissue mechanics, specifically the cellular geometry's role in longitudinal elasticity.

Decay of the water reed Phragmites communis caused by the white-rot fungus Phlebia tremellosa and the influence of some environmental factors.

The strain Phlebia tremellosa SBUG 1630 isolated from a thatched roof in Northern Germany is capable of colonizing and degrading effectively the water reed Phragmites communis. Within 96 h after inoculation, mycelia covered both the outer and the inner surface of reed shoot fragments as observed by scanning electron microscopy. Interestingly, top culm sections and culm edges were particularly susceptible towards fungal degradation. The weight loss of culms reached 20-73% depending on the environmental conditions applied during the incubation of 70 days. Reed degradation was stable at pH 4 to pH 8 and optimal between 25 and 30 °C. Short-term incubation at elevated temperatures (37 to 55 °C) affected the fungal reed degradation to only a minor extent, whereas > 18 h at 55 °C completely inhibited fungal growth and reed degradation. Supplementation with 43 mM NH4Cl enhanced the reed degradation up to 9%. In contrast, the addition of diammonium tartrate increased the weight loss of the samples considerably up to 16% at 344 mM. Furthermore, reed degradation by P. tremellosa was increased by supplementing the test medium with Mn (99 to 1584 µM), Cu (150 to 300 µM), and less significantly phosphate (4 mM), Zn (37 to 74 µM), and Ag (76 µM) after 70 days. In addition, activities of the ligninolytic enzymes laccase (max. 27.4 nmol ml-1 min-1) and lignin peroxidase (max. 22.8 nmol ml-1 min-1) were rather low in nitrogen-limited medium, whereas considerably higher levels of manganese peroxidase (max. 635.9 nmol ml-1 min-1) were observed.

Scanning electron and light microscopy of foliar epidermal characters: A tool for plant taxonomists in the identification of grasses.

SEM and light microscopy are of special interest for biologist to observe various features of the living bodies. In the current study we observed the foliar epidermal micro-morphological characters of 44 grass species using SEM and Light microscopy to assess their taxonomic utility for taxonomists in the identification process. The aim of this study is to use the foliar epidermal structural variations in both upper and lower surfaces for identification of grasses. Significant diversity was observed in both qualitative and quantitative characters using SEM and Light microscopy. Variations were observed in stomatal number, size, guard cells shape, silica bodies, macro-hairs, micro-hairs, epidermal cell number, subsidiary cells, prickles, hooks, papillae, and short and long cells. A taxonomic key is prepared using these variations for the identification of grass species. Based on these findings, SEM and Light microscopy of foliar epidermal features can be of special interest for taxonomists in the identification of complex grass taxa.

Intracellular position of mitochondria in mesophyll cells differs between C3 and C4 grasses.

In C3 plants, part of the CO2 fixed during photosynthesis in chloroplasts is released from mitochondria during photorespiration by decarboxylation of glycine via glycine decarboxylase (GDC), thereby reducing photosynthetic efficiency. The apparent positioning of most mitochondria in the interior (vacuole side of chloroplasts) of mesophyll cells in C3 grasses would increase the efficiency of refixation of CO2 released from mitochondria by ribulose 1,5-bisphosphate carboxylase/​oxygenase (Rubisco) in chloroplasts. Therefore, in mesophyll cells of C4 grasses, which lack both GDC and Rubisco, the mitochondria ought not to be positioned the same way as in C3 mesophyll cells. To test this hypothesis, we investigated the intracellular position of mitochondria in mesophyll cells of 14 C4 grasses of different C4 subtypes and subfamilies (Chloridoideae, Micrairoideae, and Panicoideae) and a C3-C4 intermediate grass, Steinchisma hians, under an electron microscope. In C4 mesophyll cells, most mitochondria were positioned adjacent to the cell wall, which clearly differs from the positioning in C3 mesophyll cells. In S. hians mesophyll cells, the positioning was similar to that in C3 cells. These results suggest that the mitochondrial positioning in C4 mesophyll cells reflects the absence of both GDC and Rubisco in the mesophyll cells and the high activity of phosphoenolpyruvate carboxylase. In contrast, the relationship between the mitochondrial positioning and enzyme distribution in S. hians is complex, but the positioning may be related to the capture of respiratory CO2 by Rubisco. Our study provides new possible insight into the physiological role of mitochondrial positioning in photosynthetic cells.

Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups.

Background and Aims: Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. Methods: A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns ( Asplenium nidus and Platycerium bifurcatum ) and angiosperms ( Arabidopsis thaliana and Commelina erecta ) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata ( Sorghum bicolor and Triticum aestivum ). Key Results: Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. Conclusions: The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution.

Museomics resolve the systematics of an endangered grass lineage endemic to north-western Madagascar.

BACKGROUND AND AIMS: Recent developments in DNA sequencing, so-called next-generation sequencing (NGS) methods, can help the study of rare lineages that are known from museum specimens. Here, the taxonomy and evolution of the Malagasy grass lineage Chasechloa was investigated with the aid of NGS. METHODS: Full chloroplast genome data and some nuclear sequences were produced by NGS from old herbarium specimens, while some selected markers were generated from recently collected Malagasy grasses. In addition, a scanning electron microscopy analysis of the upper floret and cross-sections of the rachilla appendages followed by staining with Sudan IV were performed on Chasechloa to examine the morphology of the upper floret and the presence of oils in the appendages. KEY RESULTS: Chasechloa was recovered within tribe Paniceae, sub-tribe Boivinellinae, contrary to its previous placement as a member of the New World genus Echinolaena (tribe Paspaleae). Chasechloa originated in Madagascar between the Upper Miocene and the Pliocene. It comprises two species, one of them collected only once in 1851. The genus is restricted to north-western seasonally dry deciduous forests. The appendages at the base of the upper floret of Chasechloa have been confirmed as elaiosomes, an evolutionary adaptation for myrmecochory. CONCLUSIONS: Chasechloa is reinstated at the generic level and a taxonomic treatment is presented, including conservation assessments of its species. Our study also highlights the power of NGS technology to analyse relictual or probably extinct groups.

Exploring key cellular processes and candidate genes regulating the primary thickening growth of Moso underground shoots.

The primary thickening growth of Moso (Phyllostachys edulis) underground shoots largely determines the culm circumference. However, its developmental mechanisms remain largely unknown. Using an integrated anatomy, mathematics and genomics approach, we systematically studied cellular and molecular mechanisms underlying the growth of Moso underground shoots. We discovered that the growth displayed a spiral pattern and pith played an important role in promoting the primary thickening process of Moso underground shoots and driving the evolution of culms with different sizes among different bamboo species. Different with model plants, the shoot apical meristem (SAM) of Moso is composed of six layers of cells. Comparative transcriptome analysis identified a large number of genes related to the vascular tissue formation that were significantly upregulated in a thick wall variant with narrow pith cavity, mildly spiral growth, and flat and enlarged SAM, including those related to plant hormones and those involved in cell wall development. These results provide a systematic perspective on the primary thickening growth of Moso underground shoots, and support a plausible mechanism resulting in the narrow pith cavity, weak spiral growth but increased vascular bundle of the thick wall Moso.

Early silicification of leaves and roots of seedlings of a panicoid grass grown under different conditions: anatomical relations and structural role.

Grasses accumulate high amounts of silica deposits in tissues of all their organs, especially at mature stage. However, when and under which conditions do grass seedlings begin to produce these silica deposits and their relation with anatomy and development is little known. Here we investigated the silicification process in the first leaves and roots of seedlings of Bothriochloa laguroides grown in different substrate and Si treatments. The distribution and content of silica deposits in the organs of the seedlings grown under different conditions were analyzed through staining techniques and SEM-EDAX analyses. Leaf silica deposits were accumulated 3-4 days after the first leaf emergence, also under low silica solution (0.17-0.2 mM). Their location was mainly restricted to short costal cells from basal sectors, and scarcely in trichomes and xylem at tips. Silica content in leaves increased with the age of the seedlings. Roots presented dome-shaped silica aggregates, between 4-12 µm of diameter, located in the inner tangential wall of endodermal cells and similar to those produced at maturity. Silicification begins early in the first photosynthetic leaf, and silica distribution is opposite to that found in mature plants, mainly restricted to basal sectors, probably acting as a reinforcing element. The fast incorporation of solid amorphous silica in leaves and roots, may be useful for farm applications in species that are Si-fertilized.

Physiological significance of isoprenoids and phenylpropanoids in drought response of Arundinoideae species with contrasting habitats and metabolism.

Physiological, biochemical and morpho-anatomical traits that determine the phenotypic plasticity of plants under drought were tested in two Arundinoideae with contrasting habitats, growth traits and metabolism: the fast-growing Arundo donax, which also is a strong isoprene emitter, and the slow-growing Hakonechloa macra that does not invest on isoprene biosynthesis. In control conditions, A. donax displayed not only higher photosynthesis but also higher concentration of carotenoids and lower phenylpropanoid content than H. macra. In drought-stressed plants, photosynthesis was similarly inhibited in both species, but substantially recovered only in A. donax after rewatering. Decline of photochemical and biochemical parameters, increased concentration of CO2 inside leaves, and impairment of chloroplast ultrastructure were only observed in H. macra indicating damage of photosynthetic machinery under drought. It is suggested that volatile and non-volatile isoprenoids produced by A. donax efficiently preserve the chloroplasts from transient drought damage, while H. macra invests on phenylpropanoids that are less efficient in preserving photosynthesis but likely offer better antioxidant protection under prolonged stress.

Structural Insight into Cell Wall Architecture of Micanthus sinensis cv. using Correlative Microscopy Approaches.

Structural organization of the plant cell wall is a key parameter for understanding anisotropic plant growth and mechanical behavior. Four imaging platforms were used to investigate the cell wall architecture of Miscanthus sinensis cv. internode tissue. Using transmission electron microscopy with potassium permanganate, we found a great degree of inhomogeneity in the layering structure (4-9 layers) of the sclerenchymatic fiber (Sf). However, the xylem vessel showed a single layer. Atomic force microscopy images revealed that the cellulose microfibrils (Mfs) deposited in the primary wall of the protoxylem vessel (Pxv) were disordered, while the secondary wall was composed of Mfs oriented in parallel in the cross and longitudinal section. Furthermore, Raman spectroscopy images indicated no variation in the Mf orientation of Pxv and the Mfs in Pxv were oriented more perpendicular to the cell axis than that of Sfs. Based on the integrated results, we have proposed an architectural model of Pxv composed of two layers: an outermost primary wall composed of a meshwork of Mfs and inner secondary wall containing parallel Mfs. This proposed model will support future ultrastructural analysis of plant cell walls in heterogeneous tissues, an area of increasing scientific interest particularly for liquid biofuel processing.

Full-color structured illumination optical sectioning microscopy.

In merits of super-resolved resolution and fast speed of three-dimensional (3D) optical sectioning capability, structured illumination microscopy (SIM) has found variety of applications in biomedical imaging. So far, most SIM systems use monochrome CCD or CMOS cameras to acquire images and discard the natural color information of the specimens. Although multicolor integration scheme are employed, multiple excitation sources and detectors are required and the spectral information is limited to a few of wavelengths. Here, we report a new method for full-color SIM with a color digital camera. A data processing algorithm based on HSV (Hue, Saturation, and Value) color space is proposed, in which the recorded color raw images are processed in the Hue, Saturation, Value color channels, and then reconstructed to a 3D image with full color. We demonstrated some 3D optical sectioning results on samples such as mixed pollen grains, insects, micro-chips and the surface of coins. The presented technique is applicable to some circumstance where color information plays crucial roles, such as in materials science and surface morphology.