Leaf Microstructure Research Articles

Nature-inspired architected materials using unsupervised deep learning

Nature-inspired material design is driven by superior properties found in natural architected materials and enabled by recent developments in additive manufacturing and machine learning. Existing approaches to push design beyond biomimicry typically use supervised deep learning algorithms to predict and optimize properties based on experimental or simulation data. However, these methods constrain generated material designs to abstracted labels and to “black box” outputs that are only indirectly manipulable. Here we report an alternative approach using an unsupervised generative adversarial network (GAN) model. Training the model on unlabeled data constructs a latent space free of human intervention, which can then be explored through seeding, image encoding, and vector arithmetic to control specific parameters of de novo generated material designs and to push them beyond training data distributions for broad applicability. We illustrate this end-to-end with new materials inspired by leaf microstructures, showing how biological 2D structures can be used to develop novel architected materials in 2 and 3 dimensions. We further utilize a genetic algorithm to optimize generated microstructures for mechanical properties, operating directly on the latent space. This approach allows for transfer of information across manifestations using the latent space as mediator, opening new avenues for exploration of nature-inspired materials.

A high-resolution study of PM2.5 accumulation inside leaves in leaf stomata compared with non-stomatal areas using three-dimensional X-ray microscopy

Plant leaves retain atmospheric particulate matter (PM) on their surfaces, helping PM removal and risk reduction of respiratory tract infection. Several processes (deposition, resuspension, rainfall removal) can influence the PM accumulation on leaves and different leaf microstructures (e.g., trichomes, epicuticular waxes) can also be involved in retaining PM. However, the accumulation and distribution of PM on leaves, particularly at the stomata, are unclear, and the lack of characterization methods limits our understanding of this process. Thus, in this study, we aimed to explore the pathway through which PM2.5 (aerodynamic diameter ≤ 2.5 μm) enters plant leaves, and the penetration depth of PM2.5 along the entry route. Here, an indoor experiment using diamond powder as a tracer to simulate PM2.5 deposition on leaves was carried out. Then, the treated and non-treated leaves were scanned by using three-dimensional (3D) X-ray microscopy. Next, the grayscale value of the scanned images was used to compare PM2.5 accumulation in stomatal and non-stomatal areas of the treated and non-treated leaves, respectively. Finally, a total PM2.5 volume from the abaxial epidermis was calculated. The results showed that, first, a large amount of PM2.5 accumulates within leaf stomata, whereas PM2.5 does not accumulate at non-stomatal areas. Then, the penetration depth of PM2.5 in stomata of most tree species was 5–14 μm from the abaxial epidermis. For the first time, 3D X-ray microscope scanning was used to confirm that a pathway by which PM2.5 enters the leaves is through the stomata, which is fundamental for further research on how PM2.5 translocates and interacts with tissues and cells in leaves.

Leaf microstructure and photosynthetic characteristicsof a rice midvein-deficient mutant dl-14

Midvein is an important structure of the upright leaf of rice, and its normal development is essential to the formation of a common plant type of rice (Oryza sativa L.). To reveal the effect of midvein deficiency on photosynthesis-related characteristics, leaf microstructure, and vein characteristics, the photosynthetic features between the midvein-deficient mutant dl-14 and wild-type Huanghuazhan plants were analyzed. The results indicated that the midvein area of the dl-4 mutant lacked large intercellular space and instead it was filled with mesophyll cells. Moreover, the vein density of the dl-14 mutant was significantly higher than that in cv. Huanghuazhan. Chlorophyll (Chl) a, Chl b, and carotenoid content were markedly elevated in dl-14. In terms of photosynthetic characteristics, we observed that under high irradiance and high CO2 concentration, the net photosynthetic rate of dl-14 plants was significantly higher than that of Huanghuazhan plants, but its water use efficiency was significantly lower. In addition, several major photosynthetic parameters, including characteristics of chlorophyll fluorescence (the efficiency of excitation capture of open PS II center, photochemical quenching, effective quantum yield of PS II photochemistry, and electron transfer rate) were significantly higher in dl-14 plants compared to Huanghuazhan plants, but the nonphotochemical quenching of dl-14 mutant was significantly lower than that of Huanghuazhan. These findings indicate that the dl-14 mutant has higher vein density, stronger photon conversion ability, and weaker radiation dissipation ability. This study can provide theoretical support for breeders to use the midvein-deficient mutant.

Perspectives On Bioinspired Product Development: Entrapping Surfaces Based On Leaf Microstructures.

Scientists who work on bioinspired systems may see the potential for products resulting from their research, but are often unaware of the various steps or issues related to commercialization or product development. Commercialization topics lie outside the usual training of a basic biologist, and therefore much of their exposure to these topics is adventitious, such as from casual conversations at meetings. Thus, the information gleaned may be somewhat piecemeal. In this paper, I briefly summarize some of what I have learned over the last ten years about commercialization from a variety of different sources, related to a bioinspired project in which I am involved. My collaborators and I have invented and patented a technology to entrap insect pests by a purely physical mechanism (a "physical insecticide" that does not involve a chemical insecticide). This bioinspired technology is based on a historical control method, in which leaves from bean plants were used to capture bed bugs for hundreds of years in parts of Eastern Europe. Sharp recurved microstructures (nonglandular trichomes) on the leaf surfaces irreversibly impale the tarsi (feet) of the bed bugs as they walk over the surfaces, trapping them in place. Pest professionals have identified bed bugs as the most difficult pest to control; there is a clear need for new methods of control for this pest. There are societal benefits and consumer demand for products that are sustainable, without regulatory constraints, and that minimize insecticide exposure for humans. But how would these products be developed from this starting point of a bioinspired invention? I will briefly share some of our experiences in the early and ongoing product development of entrapping surfaces, with the hope that this might interest or aid others who are considering entrepreneurial activities. Unfamiliar topics such as intellectual property, customer segmentation, value propositions, business models, conflict of interest, and conflict of commitment may require some attention from prospective entrepreneurs. This brief and introductory overview is intended for those academic scientists with little to no experience or knowledge in the area of commercialization.

Relationship between leaf dust retention capacity and leaf microstructure of six common tree species for campus greening

Green plants can effectively retain atmospheric particle pollution and purify the air. As an important part of the campus ecosystem, they have a significant effect on absorbing atmospheric pollutants and improving the quality of the campus air environment. Six common greening plants were selected as the object in Xiangnan University. The dust retention capacity of plant leaves, leaf micro-structure, and leaf contact angle were measured. The results show that the highest amounts of dust removed by Osmanthus fragrans Lour was 3.451 g/m2, and the least amounts of dust removed by Magnolia denudata Desr. was 1.005 g/m2, and the maximum is 4.148 times of the minimum. The micro-structure of the plant leaf surface affects the amount of dust retention. The plant dust retention capacity with gully of the leaf surface and fluff, stomata, and sawtooth structure is relatively strong; The plant dust retention capacity with smooth, wax layer, leathery, and gully is relatively weak. The leaf contact area of a plant is related to its dust retention ability, that is, when the measured leaf contact angle is <90°, the leaf dust retention ability of the plant is strong. When the blade contact angle is >90°, the dust retention capacity is weak.

Impacts of Slow-Release Nitrogen Fertilizer Rates on the Morpho-Physiological Traits, Yield, and Nitrogen Use Efficiency of Rice under Different Water Regimes

The efficient use of water and fertilizer is vital for optimizing plant growth and yield in rice production. To achieve sustainable rice production and resource management, the ways in which applied water and nitrogen affect the root and shoot morpho-physiology, as well as yield, must be understood. In this study, a pot experiment was conducted to investigate the effects of slow-release nitrogen fertilizer (sulfur-coated urea) application at three levels (light nitrogen (NL), medium nitrogen (NM), and heavy nitrogen (NH)) on the growth, yield, and nitrogen use efficiency (NUE) of rice grown under three water regimes (wetting and soil saturation (WSS), wetting and moderate drying (WMD) and wetting and severe drying (WSD)). The results revealed that differences in water regimes and fertilizer rates led to significant differences in the roots, shoots, yield, and NUE of rice. Increasing the N dosage by 5% enhanced the root and biomass production by 16% in comparison with that of the other groups. The NH×WSS treatment produced the greatest root length, weight, density, active absorption, and oxidation. However, the integration of WSS × NL generated the maximum value of nitrogen apparent recovery efficiency (63.1% to 67.6%) and the greatest value of nitrogen partial factor productivity (39.9 g g−1 to 41.13 g g−1). Transmission electron microscopy (TEM) images showed that plants grown under high and medium nitrogen fertilizer rates with WSS had improved leaf mesophyll structure with normal starch grains, clear cell walls, and well-developed chloroplasts with tidy and well-arranged thylakoids. These results show that TEM images are useful for characterizing the nitrogen and water status of leaves in the sub-micrometer range and providing specific information regarding the leaf microstructure. The findings of this study suggest that the application of NH×WSS can produce improvements in growth traits and increase rice yield; however, the NL×WSS treatment led to greater NUE, and the authors recommend its usage in rice agriculture.

Urban road greenbelt configuration: The perspective of PM2.5 removal and air quality regulation.

The establishment of the road green belt (RGB) is an effective means to reduce particle matter (PM2.5) emissions from road traffic. This study tested the ability of 23 common tree species in Shenzhen to reduce PM2.5 concentrations using field investigations and wind tunnel tests. The association between leaf microstructure and individual reduction ability was also analyzed. Finally, the impact of three RGB configurations (i.e., arbor, shrub, arbor+shrub) on road PM2.5 dispersion and deposition was simulated using the ENVI-met three-dimensional aerodynamic model, based on which an optimal RGB configuration was proposed. There were three key findings of the tests. First, the wind speed was the main factor affecting the PM2.5 concentration (54.2%), followed by vehicle flow (27.7%), temperature (14.2%), and time factor (7.6%). Second, the range of dry deposition velocity (Vd) was 0.04-6.4m/s, and the dominant dust-retaining plant species were the evergreen trees, Ficus microcarpa and Ficus altissima, and the evergreen shrubs, Codiaeum variegatum and Fagraea ceilanica. A higher proportion of grooves or larger stomata would increase the probability that the blade would capture PM2.5. Third, the shrub RGB demonstrated the best performance in terms of pollutant dispersion; its PM2.5 concentration at the respiratory height (RH, 1.5m) on the pedestrian crossing was 15-20% lower than the other RGB configurations. In terms of pollutant deposition, the arbor+shrub composite RGB was two-fold better than the other RGB configurations. Moreover, it was more advantageous to plant shrub RGBs in street canyons to achieve a balance between the lowest concentration and the largest deposition of PM2.5 pollutants. The findings of this study will facilitate the RGB configurations with good dust retention ability.

Influence of Green Light Added with Red and Blue LEDs on the Growth, Leaf Microstructure and Quality of Spinach (Spinacia oleracea L.)

The aim of this study was to investigate the effects of green light, added with red and blue LEDs, on the growth, leaf microstructure and quality of spinach plants. Plants were transplanted and grown hydroponically for 30 days under different combinations of red:blue with a 4:1 ratio (R4B1), red:blue:green with a 5:2:3 ratio (R5B2G3) and red:blue:green with a 1:1:1 ratio (R1B1G1), at a 190 µmoL m−2·s−1 photosynthetic photon flux density (PPFD). The results showed that green light, added to red and blue LEDs at a reasonable ratio, could reduce the growth, leaf microstructure and quality of spinach plants, but not the organic acid content. The highest values for the growth parameters, photosynthetic pigments, leaf structure characteristics and quality of the spinach plant were observed for the R4B1 treatment, but not for the organic acid content. Therefore, our results suggest that green light added to red and blue LEDs at a reasonable ratio is not suitable for the growth of spinach.

Cytokinin drives assembly of the phyllosphere microbiome and promotes disease resistance through structural and chemical cues.

The plant hormone cytokinin (CK) is an important developmental regulator, promoting morphogenesis and delaying differentiation and senescence. From developmental processes, to growth, to stress tolerance, CKs are central in plant life. CKs are also known to mediate plant immunity and disease resistance, and several classes of microbes can also produce CKs, affecting the interaction with their plant hosts. While host species and genotype can be a driving force in shaping the plant microbiome, how plant developmental hormones such as CK can shape the microbiome is largely uninvestigated. Here, we examined the relationship between CK and the phyllosphere microbiome, finding that CK acts as a selective force in microbiome assembly, increasing richness, and promoting the presence of Firmicutes. CK-mediated immunity was found to partially depend on the microbial community, and bacilli isolated from previously described CK-rich plant genotypes, which overexpress a CK biosynthesis gene or have increased CK sensitivity, induced plant immunity, and promoted disease resistance. Using a biomimetic system, we investigated the relationship between the leaf microstructure, which is differentially patterned upon changes in CK content or signaling, and the growth of different phyllosphere microbes. We found that leaf structures derived from CK-rich plant genotypes support bacilli in the biomimetic system. CK was able to promote the growth, swarming, and biofilm formation of immunity inducing bacillus isolates in vitro. Overall, our results indicate that host genotype and hormonal profiles can act as a strong selective force in microbiome assembly, underlying differential immunity profiles, and pathogen resistance as a result.

Comparative transcriptome and cross-section analyses provide insights into the mechanisms underlying Sargassum fusiforme responses to the harmful algal bloom-forming dinoflagellate Karenia mikimotoi

The impacts of harmful algal blooms (HABs) on macrophytes have rarely been studied, although HABs are currently considered one of the major worldwide marine environmental threats. In this study, we incorporated photophysiology experimental data with paraffin-embedded section and transcriptome analysis of S. fusiforme to explore the effects of dense K. mikimotoi culture on the growth, photosynthetic activities, and leaf microstructure of S. fusiforme, as well as the expression of the genes related to its photosynthesis. The results showed that the fresh weight, Chl a contents, apparent photosynthetic efficiency (α) and relative electron transfer rate (rETRmax) of S. fusiforme seedlings cultivated for ten days with K. mikimotoi decreased by 53.60 %, 13.48 %, 6.30 % and 36.51 %, as compared with those cultivated without K. mikimotoi. The leaves of the S. fusiforme seedlings began to rot and detach from the stems after a week of cultivation with K. mikimotoi, and additional epidermic cells decomposed with prolonged exposure to the dinoflagellate. Transcripts of the genes related to photosystem reaction center subunits and photosynthesis antenna proteins were expressed differentially during the cultivation with K. mikimotoi, consistent with changes in the photosynthesis of S. fusiforme seedlings. These combined results indicate that the main mechanism for resistance to HABs is the formation of epidermis by a layer of tightly arranged cylindrical cells combined with differential expression of the photosynthesis-related genes.

Synthesis of silver@platinum-cobalt nanoflower on reduced graphene oxide as an efficient catalyst for oxygen reduction reaction

A novel oxygen reduction reaction (ORR) electrocatalyst silver@platinum-cobalt-rGO nanoflower (Ag@PtCo-rGO NFs) is prepared by hydrothermal reduction method. The formation of silver chloride likes elm leaf microstructure in the reaction process, performing as a template. The Ag@PtCo-rGO NFs exhibit excellent electrocatalytic activity, whose specific activity is 9 times higher than that of commercial Pt/C. More importantly, Ag@PtCo-rGO NFs demonstrate excellent durability than JM Pt/C for ORR in acid media, as evidenced by accelerated durability test after 40,000 cycles. These excellent performances can be attributed to the special structure, atomic steps and synergistic effect between Pt, Ag and Co. The density functional theory calculation shows that Ag@PtCo has the best activity, which is related to the transition state for O–O bond. This work proposes a promising pathway for the synthesis of surfactant-free nanoflowers structure catalysts with high catalytic performance and low cost.

Leaf transcriptomic response mediated by cold stress in two maize inbred lines with contrasting tolerance levels

Maize (Zea mays L.) is a thermophilic plant and a minor drop in temperature can prolong the maturity period. Plants respond to cold stress through structural and functional modification in cell membranes as well as changes in the photosynthesis and energy metabolism. In order to understand the molecular mechanisms underlying cold tolerance and adaptation, we employed leaf transcriptome sequencing together with leaf microstructure and relative electrical conductivity measurements in two maize inbred lines, having different cold stress tolerance potentials. The leaf physiological and transcriptomic responses of maize seedlings were studied after growing both inbred lines at 5 °C for 0, 12 and 24 h. Differentially expressed genes were enriched in photosynthesis antenna proteins, MAPK signaling pathway, plant hormone signal transduction, circadian rhythm, secondary metabolites related pathways, ribosome, and proteasome. The seedlings of both genotypes employed common stress responsive pathways to respond to cold stress. However, the cold tolerant line B144 protected its photosystem II from photooxidation by upregulating D1 proteins. The sensitive line Q319 was unable to close its stomata. Collectively, B144 exhibited a cold tolerance owing to its ability to mediate changes in stomata opening as well as protecting photosystem. These results increase our understanding on the cold stress tolerance in maize seedlings and propose multiple key regulators of stress responses such as modifications in photosystem II, stomata guard cell opening and closing, changes in secondary metabolite biosynthesis, and circadian rhythm. This study also presents the signal transduction related changes in MAPK and phytohormone signaling pathways in response to cold stress during seedling stage of maize.

Surface-Based Analysis of Leaf Microstructures for Adsorbing and Retaining Capability of Airborne Particulate Matter in Ten Woody Species

We evaluated surface-based analysis for assessing the possible relationship between the microstructural properties and particulate matter (i.e., two size fractions of PM2.5 and PM10) adsorption efficiencies of their leaf surfaces on ten woody species. We focused on the effect of PM adsorption capacity between micro-morphological features on leaf surfaces using a scanning electron microscope and a non-contact surface profiler as an example. The species with higher adsorption of PM10 on leaf surfaces were Korean boxwood (Buxus koreana Nakai ex Chung &amp; al.) and evergreen spindle (Euonymus japonicus Thunb.), followed by yulan magnolia (Magnolia denudata Desr.), Japanese yew (Taxus cuspidata Siebold &amp; Zucc.), Japanese horse chestnut (Aesculus turbinata Blume), retusa fringetree (Chionanthus retusus Lindl. &amp; Paxton), maidenhair tree (Ginkgo biloba L.), and royal azalea (Rhododendron schlippenbachii Maxim.). There was a higher capacity for the adsorption of PM2.5 on the leaf surfaces of B. koreana and T. cuspidata, followed by A. turbinata, C. retusus, E. japonicus, G. biloba, and M. denudata. In wax layer tests, T. cuspidata, A. turbinata, R. schlippenbachii, and C. retusus showed a statistically higher PM2.5 capturing capacity than the other species. Different types of trichomes were distributed on the adaxial and abaxial leaves of A. turbinata, C. retusus, M. denudata, pagoda tree (Styphnolobium japonicum (L.) Schott), B. koreana, and R. schlippenbachii; however, these trichomes were absent on both sides of the leaves of G. biloba, tuliptree (Liriodendron tulipifera L.), E. japonicus, and T. cuspidata. Importantly, leaf surfaces of G. biloba and S. japonicum with dense or thick epicuticular leaf waxes and deeper roughness revealed lower PM adsorption. Based on the overall performance of airborne PM capture efficiency, evergreen species such as B. koreana, T. cuspidata, and E. japonicus showed the best results, whereas S. japonicum and L. tulipifera had the lowest capture. In particular, evergreen shrub species showed higher PM2.5 depositions inside the inner wall of stomata or the periphery of guard cells. Therefore, in leaf microstructural factors, stomatal size may be related to notably high PM2.5 holding capacities on leaf surfaces, but stomatal density, trichome density, and roughness had a limited effect on PM adsorption. Finally, our findings indicate that surface-based microstructures are necessarily not a correlation for corresponding estimates with leaf PM adsorption.

Biomimetic Replication of Root Surface Microstructure using Alteration of Soft Lithography.

Biomimetics is the use of chemistry and material sciences to mimic biological systems, specifically biological structures, to better humankind. Recently, biomimetic surfaces mimicking the microstructure of leaf surface, were used to study the effects of leaf microstructure on leaf-environment interactions. However, no such tool exists for roots. We developed a tool allowing the synthetic mimicry of the root surface microstructure into an artificial surface. We relied on the soft lithography method, known for leaf surface microstructure replication, using a two-step process. The first step is the more challenging one as it involves the biological tissue. Here, we used a different polymer and curing strategy, relying on the strong, rigid, polyurethane, cured by UV for the root molding. This allowed us to achieve a reliable negative image of the root surface microstructure including the delicate, challenging features such as root hairs. We then used this negative image as a template to achieve the root surface microstructure replication using both the well-established polydimethyl siloxane (PDMS) as well as a cellulose derivative, ethyl cellulose, which represents a closer mimic of the root and which can also be degraded by cellulase enzymes secreted by microorganisms. This newly formed platform can be used to study the microstructural effects of the surface in root-microorganism interactions in a similar manner to what has previously been shown in leaves. Additionally, the system enables us to track the microorganism's locations, relative to surface features, and in the future its activity, in the form of cellulase secretion.

In Vitro Regeneration, Ex Vitro Rooting and Foliar Stoma Studies of Pseudostellaria heterophylla (Miq.) Pax

Pseudostellaria heterophylla, in the family Caryophyllaceae, is an important Chinese medicinal plant commonly used to treat various diseases in children and valued for its ornamental properties. In this study, nodal segments were obtained from wild plants and used as explants to develop an efficient micropropagation protocol for this species. Murashige and Skoog (MS) medium supplemented with 1.5 mg·L−1 6-benzyladenine (6-BA) was the most suitable medium for inducing axillary buds and enhancing their growth, and MS medium containing 0.1 mg·L−1 indole-3-butyric acid (IBA) was the most effective for inducing in vitro rooting. To reduce labor, time, and cost, microshoots were rooted under ex vitro conditions. Pretreatments of the shoots with 100 mg·L−1 naphthaleneacetic acid (NAA) for 1 min ensured successful rooting in 86.7% of shoots. Comparison of the leaf microstructure between in vitro- and ex vitro-rooted plantlets revealed abnormal stomatal apparatus in the former. The stomatal apparatus of ex vitro plantlets were normal, although the stomatal density was reduced, which indicated that these plantlets were more likely to be able to adapt to environmental conditions in the field. We identified the optimal medium for P. heterophylla multiplication with respect to increased rooting efficiency of micropropagated shoots under ex vitro conditions. This results presented here will be helpful for agricultural cultivation of P. heterophylla.

Response of the particulate matter capture ability to leaf age and pollution intensity.

Differences in leaf surface microstructure characteristics can lead to differences in the ability of trees to capture suspended particulate matter (PM). The influence of changes in leaf surface microstructure caused by growth and environmental pollution on the PM capture ability is poorly understood. This study assessed the influence of growth on leaf microstructure in leaves of different ages, and the influence of pollution intensity was assessed by studying trees growing under different pollution conditions. It was found that the ability of leaves of Taxus cuspidata var., Platycladus orientalis, and Pinus tabuliformis to absorb total suspended particles (TSP), PM10, PM2.5, and PM1 increased with leaf age. The amounts of TSP and PM10 captured by P. orientalis, P. tabuliformis, Sophora japonica, Populus tomentosa, and Ginkgo biloba were higher in heavily polluted areas than in clean areas. This may be because particle capture is influenced by leaf microstructure changes. With age increasing, the root mean square roughness (Rq) of three evergreen species leaves increased. Environmental pollution will change the leaf surface microstructure and its ability to capture PM. Compared with a clean area, in a heavily polluted area, the stomatal index of the leaves decreased, stomata were occluded, the leaf wax layer was degraded, the leaf surface contained more particles, the surface texture of S. japonica and G. biloba leaves became irregular, the boundaries of the epidermal cells became more irregular, and the trichrome of S. japonica became thinner, longer, and harder. The Rq value was generally higher in the heavily polluted area, and the roughness of the abaxial surface increased more than on the adaxial surface. In the heavily polluted area, the leaf microstructure changes were the main reason for the increase in the Rq value. With the increase in leaf roughness, the amount of PM on the leaf surface increased.

A biomimetic platform for studying root-environment interaction

AimsMicrostructure plays an important role in biological systems. Microstructural features are critical in the interaction between two biological organisms, for example, a microorganism and the surface of a plant. However, isolating the structural effect of the interaction from all other parameters is challenging when working directly with the natural system. Replicating microstructure of leaves was recently shown to be a powerful research tool for studying leaf-environment interaction. However, no such tool exists for roots. Roots present a special challenge because of their delicacy (specifically of root hairs) and their 3D structure. We aim at developing such a tool for roots.MethodsBiomimetics use synthetic systems to mimic the structure of biological systems, enabling the isolation of structural function. Here we present a method which adapts tools from leaf microstructure replication to roots. We introduce new polymers for this replication.ResultsWe find that Polyurethane methacrylate (PUMA) with fast UV curing gives a reliable replication of the tomato root surface microstructure. We show that our system is compatible with the pathogenic soilborne bacterium Ralstonia solanacearum.ConclusionsThis newly developed tool may be used to study the effect of microstructure, isolated from all other effects, on the interaction of roots with their environment.

Identification and Expression Pattern Analysis of Bacterial Blight Resistance Genes in Oryza officinalis Wall ex Watt Under Xanthomonas oryzae Pv. oryzae Stress

BackgroundBacterial blight (BB) caused by Xanthomonas oryzae Pv. oryzae (Xoo) is one of the most serious diseases of rice worldwide. Oryza officinalis Wall ex Watt, harboring abundant genetic diversity and disease resistance features, are important resources of exploring resistance genes with broad-spectrum resistance to BB. However, the molecular mechanisms and genes of BB resistance in O. officinalis have been rarely explored.ResultsHere, the BB resistance of four different origin O. officinalis populations in Yunnan were identified by seven representative hypervirulent Xoo races, which exhibited different BB resistance among four populations, in which the BB resistance of the Gengma_Lincang population was the strongest. In addition, the pathogenetic ability of seven Xoo races to O. officinalis was different in that the pathogenicity of PXO99 was stronger than that of C5. There were no remarkable differences in leaf microstructures among four O. officinalis populations, revealing the differences in resistance of four O. officinalis to BB are caused by the endogenous resistance genes. Furthermore, our results proved that there were no nine cloned BB resistance genes in four populations but possessed dominant Xa5, dominant Xa13, and recessive xa3/xa26 homologous alleles of xa5, xa13, and Xa3/Xa26 resistance genes. These three homologous genes were isolated and cloned from four populations and named OoXa5, OoXa13, and Ooxa3/xa26. The expression profile revealed that the expression levels of OoXa13 and Ooxa3/xa26 were significantly down-regulated under PXO99 and C5 stress, especially in the Gengma_Lincang population, suggesting the O. officinalis might enhance BB resistance by down-regulating the expression level of OoXa13 and Ooxa3/xa26.ConclusionThe BB resistance genes of O. officinalis had its own characteristics by expression pattern and BLAST analysis of OoXa5, OoXa13, and Ooxa3/xa26, which indicated that there might be new genes or molecular mechanism of BB resistance in O. officinalis. Our studies provided a solid foundation and reference for revealing the molecular mechanism of BB resistance in O. officinalis.

The Removal Efficiencies of Several Temperate Tree Species at Adsorbing Airborne Particulate Matter in Urban Forests and Roadsides

Although urban trees are proposed as comparatively economical and eco-efficient biofilters for treating atmospheric particulate matter (PM) by the temporary capture and retention of PM particles, the PM removal effect and its main mechanism still remain largely uncertain. Thus, an understanding of the removal efficiencies of individual leaves that adsorb and retain airborne PM, particularly in the sustainable planning of multifunctional green infrastructure, should be preceded by an assessment of the leaf microstructures of widespread species in urban forests. We determined the differences between trees in regard to their ability to adsorb PM based on the unique leaf microstructures and leaf area index (LAI) reflecting their overall ability by upscaling from leaf scale to canopy scale. The micro-morphological characteristics of adaxial and abaxial leaf surfaces directly affected the PM trapping efficiency. Specifically, leaf surfaces with grooves and trichomes showed a higher ability to retain PM as compared to leaves without epidermal hairs or with dynamic water repellency. Zelkova serrata (Thunb.) Makino was found to have significantly higher benefits with regard to adsorbing and retaining PM compared to other species. Evergreen needle-leaved species could be a more sustainable manner to retain PM in winter and spring. The interspecies variability of the PM adsorption efficiency was upscaled from leaf scale to canopy scale based on the LAI, showing that tree species with higher canopy density were more effective in removing PM. In conclusion, if urban trees are used as a means to improve air quality in limited open spaces for urban greening programs, it is important to predominantly select a tree species that can maximize the ability to capture PM by having higher canopy density and leaf grooves or trichomes.

Metamaterial architecture from a self-shaping carnivorous plant

As meticulously observed and recorded by Darwin, the leaves of the carnivorous plant Drosera capensis L. slowly fold around insects trapped on their sticky surface in order to ensure their digestion. While the biochemical signaling driving leaf closure has been associated with plant growth hormones, how mechanical forces actuate the process is still unknown. Here, we combine experimental tests of leaf mechanics with quantitative measurements of the leaf microstructure and biochemistry to demonstrate that the closure mechanism is programmed into the cellular architecture of D. capensis leaves, which converts a homogeneous biochemical signal into an asymmetric response. Inspired by the leaf closure mechanism, we devise and test a mechanical metamaterial, which curls under homogeneous mechanical stimuli. This kind of metamaterial could find possible applications as a component in soft robotics and provides an example of bio-inspired design.