Determination of optimal NH4+/K + concentration and corresponding ratio critical for growth of tobacco seedlings in a hydroponic system.

Inherently, ammonium (NH4 +) is critical for plant growth; however, its toxicity suppresses potassium (K+) uptake and vice-versa. Hence, attaining a nutritional balance between these two ions (NH4 + and K+) becomes imperative for the growth of tobacco seedlings. Therefore, we conducted a 15-day experimental study on tobacco seedlings exposed to different concentrations (47 treatments) of NH4 +/K+ at different corresponding 12 ratios simultaneously in a hydroponic system. Our study aimed at establishing the optimal NH4 +-K+ concentration and the corresponding ratio required for optimal growth of different tobacco plant organs during the seedling stage. The controls were the baseline for comparison in this study. Plants with low or excessive NH4 +-K+ concentration had leaf chlorosis or dark greenish colouration, stunted whole plant part biomass, and thin roots. We found that adequate K+ supply is a pragmatic way to mitigate NH4 +-induced toxicity in tobacco plants. The optimal growth for tobacco leaf and root was attained at NH4 +-K+ concentrations 2-2 mM (ratio 1:1), whereas stem growth was optimal at NH4 +-K+ 1-2 mM (1:2). The study provided an insight into the right combination of NH4 +/K+ that could mitigate or prevent NH4 + or K+ stress in the tobacco seedlings.

Bioinspired magnetism-responsive hybrid microstructures with dynamic switching toward liquid droplet rolling states.

The functionality of tunable liquid droplet adhesion is crucial for many applications such as self-cleaning surfaces and water collectors. However, it is still a challenge to achieve real-time and fast reversible switching between isotropic and anisotropic liquid droplet rolling states. Inspired by the surface topography on lotus leaves and rice leaves, herein we report a biomimetic hybrid surface with gradient magnetism-responsive micropillar/microplate arrays (GMRMA), featuring dynamic fast switching toward different droplet rolling states. The exceptional dynamic switching characteristics of GMRMA are visualized and attributed to the fast asymmetric deformation between the two different biomimetic microstructures under a magnetic field; they endow the rolling droplets with anisotropic interfacial resistance. Based on the exceptional morphology switching surface, we demonstrate the function of classification and screening of liquid droplets, and thus propose a new strategy for liquid mixing and potential microchemical reactions. It is expected that this intelligent GMRMA will be conducive to many engineering applications, such as microfluidic devices and microchemical reactors.

Overcoming Long-Range Unidirectional Transport of Underwater Bubbles on Laser-Textured Single-Layer Superaerophobic Dual-Rail Arrays.

Understanding the behavior of gas bubbles in aqueous media has been a hot topic because of their vital roles in both scientific research and industrial applications. Wettability gradient force and Laplace pressure are two typical characteristics of bubble transport. However, most work about bubble transport is limited to a short distance. Therefore, we took inspiration from the structure of the Nepenthes pitcher and prepared superaerophobic dual-rail arrays (SDRA). Upon SDRA, with this structure of a uniform distribution of superaerophobic and superaerophilic zones, bubbles can be transported over long distances on the structure's surface. The underlying principle is that gas bubbles tend to spread out on the superaerophilic region until they make contact with the asymmetric superaerophobic barriers. An asymmetric spreading resistance force is generated, which is attributed to the different lengths of the three-phase contact line (TCL) between gas bubbles and superaerophobic barriers. In addition, diverse parameters are quantified to investigate the critical transport state between unidirection and bidirection. Under the function of SDRA, the structure surface can realize bubble collection. The transporter as well as the light-control-light shutter is also successfully deployed. The present study will inspire people to develop innovative strategies to effectively manipulate gas bubbles in practical applications.

Active Droplet Transport Induced by Moving Meniscus on a Slippery Magnetic Responsive Micropillar Array.

Intelligent droplet manipulation plays a crucial role in both scientific research and industrial technology. Inspired by nature, meniscus driving is an ingenious way to spontaneously transport droplets. However, the shortages of short-range transport and droplet coalescence limit its application. Here, an active droplet manipulation strategy based on the slippery magnetic responsive micropillar array (SMRMA) is reported. With the aid of a magnetic field, the micropillar array bends and induces the infusing oil to form a moving meniscus, which can attract nearby droplets and transport them for a long range. Significantly, clustered droplets on SMRMA can be isolated by micropillars, avoiding droplet coalescence. Moreover, through adjusting the arrangement of the micropillars of SMRMA, multi-functional droplet manipulation such as unidirectional droplet transport, multi-droplet transport, droplet mixing, and droplet screening can be achieved. This work provides a promising approach for intelligent droplet manipulation and unfolds broad application prospects in microfluidics, microchemical reaction, biomedical engineering, and other fields.

Unlocking the potentials of nitrate transporters at improving plant nitrogen use efficiency.

Nitrate ( NO 3 - ) transporters have been identified as the primary targets involved in plant nitrogen (N) uptake, transport, assimilation, and remobilization, all of which are key determinants of nitrogen use efficiency (NUE). However, less attention has been directed toward the influence of plant nutrients and environmental cues on the expression and activities of NO 3 - transporters. To better understand how these transporters function in improving plant NUE, this review critically examined the roles of NO 3 - transporters in N uptake, transport, and distribution processes. It also described their influence on crop productivity and NUE, especially when co-expressed with other transcription factors, and discussed these transporters' functional roles in helping plants cope with adverse environmental conditions. We equally established the possible impacts of NO 3 - transporters on the uptake and utilization efficiency of other plant nutrients while suggesting possible strategic approaches to improving NUE in plants. Understanding the specificity of these determinants is crucial to achieving better N utilization efficiency in crops within a given environment.

Multiple-Droplet Selective Manipulation Enabled by Laser-Textured Hydrophobic Magnetism-Responsive Slanted Micropillar Arrays with an Ultrafast Reconfiguration Rate.

Biomimetic structures based on the magnetic response have attracted ever-increasing attention in droplet manipulation. Till now, most methods for droplet manipulation by a magnetic response are only applicable to a single droplet. It is still a challenge to achieve on-demand and precise control of multiple droplets (≥2). In this paper, a strategy for on-demand manipulation of multiple droplets based on magnetism-responsive slanted micropillar arrays (MSMAs) is proposed. The Glaco-modified superhydrophobic surface is the basis of multiple-droplet manipulation. The droplet's motion mode (pinned, unidirectional, and bidirectional) can be readily fine-tuned by changing the volume of droplets and the speed of the magnetic field. The rapid movement of droplets (10-80 mm/s) in the horizontal direction is realized by the unidirectional waves of the micropillar array driven by a specific magnetic field. The bending angle of micropillars can be rapidly and reversibly adjusted from 0 to 90° under the action of a magnetic field. Meanwhile, the liquid-involved light, electric switch, and biomedical detection can be designed by manipulating the droplets on demand. The superiority of MSMAs in multiple-droplet programmable manipulation opens up an avenue for applications in microfluidic and biomedical engineering.

Differential Effects of Ammonium (NH4+) and Potassium (K+) Nutrition on Photoassimilate Partitioning and Growth of Tobacco Seedlings.

Plants utilize carbohydrates as the main energy source, but much focus has been on the impact of N and K on plant growth. Less is known about the combined impact of NH4+ and K+ nutrition on photoassimilate distribution among plant organs, and the resultant effect of such distribution on growth of tobacco seedlings, hence this study. Here, we investigated the synergetic effect of NH4+ and K+ nutrition on photoassimilate distribution, and their resultant effect on growth of tobacco seedlings. Soluble sugar and starch content peaks under moderate NH4+ and moderate K+ (2-2 mM), leading to improved plant growth, as evidenced by the increase in tobacco weight and root activity. Whereas, a drastic reduction in the above indicators was observed in plants under high NH4+ and low K+ (20-0.2 mM), due to low carbohydrate synthesis and poor photoassimilate distribution. A strong positive linear relationship also exists between carbohydrate (soluble sugar and starch) and the activities of these enzymes but not for invertase. Our findings demonstrated that NH4+ and K+-induced ion imbalance influences plant growth and is critical for photoassimilate distribution among organs of tobacco seedlings.

On-Demand Maneuver of Millirobots with Reprogrammable Motility by a Hard-Magnetic Coating.

Millirobots that can be actuated and accurately steered by external magnetic fields, are highly desirable for bioengineering and wearable devices. However, existing designs of millirobots are limited by their specific material composition, hindering their wider application due to a lack of scalability. Here, we present a method for the generation of heterogeneous magnetic millirobots based on magnetic coatings. The coatings, composed of hard-magnetic CrO2 particles dispersed in an adhesive solution, impart magnetic actuation to diverse substrates with planar sheets or 3D structures. Millirobots constructed from the coatings can be readily reprogrammed with intricate magnetization profiles using laser localized heating, enabling reconfigurable shape changes under magnetic actuation. Using this approach, we demonstrate on-demand maneuvering capability of reconfiguring locomotion involving crawling, overturning and rolling with a single millirobot. Various functions, including the ability to catch a fast-moving ball, object transportation, and targeted assembly, have been achieved. This adhesive strategy facilitates the design of millirobots and may open avenues to the creation of complex millirobots for broad applications.

Meniscus-Induced Directional Self-Transport of Submerged Bubbles on a Slippery Oil-Infused Pillar Array with Height-Gradient.

Directional manipulation of submerged bubbles is fundamental for both theoretical research and industrial production. However, most current strategies are limited to the upward motion direction, complex surface topography, and additional apparatuses. Here, we report a meniscus-induced self-transport platform, namely, a slippery oil-infused pillar array with height-gradient (SOPAH) by combining femtosecond laser drilling and replica mold technology. Owing to the unbalanced capillary force and Laplace pressure difference, bubbles on SOPAH tend to spontaneously transport along the meniscus gradient toward a higher elevation. The self-transport performances of bubbles near the pillars depend on the complex meniscus shape. Significantly, to understand the underlying transport mechanism, the 3D meniscus profile is simulated by solving the Young-Laplace equation. It is found that the concave valleys formed between the adjacent pillars can change the gradient direction of the meniscus and lead to the varied transport performances. Finally, by taking advantage of a water electrolysis system, the assembled SOPAH serving as a bubble-collecting device is successfully deployed. This work should not only bring new insights into the meniscus-induced self-transport dynamics but also benefit potential applications in the field of intelligent bubble manipulation.

The responses of soil organic carbon and total nitrogen to chemical nitrogen fertilizers reduction base on a meta-analysis.

Soil organic carbon (SOC), total nitrogen (TN), and their ratio (C:N) play important roles in preserving soil fertility, and their values are closely related to fertilizer use. However, the overall trend and magnitude of changes in SOC, TN and C:N in response to chemical nitrogen fertilizers reduction remain inconclusive. Here, the meta-analysis conducted comparisons at 48 sites covering various cropping system, soil type, and climatic regions of China to investigate the responses of SOC, TN and C:N to chemical nitrogen fertilizers reduction. The results showed that chemical nitrogen fertilizers reduction decreased SOC by 2.76 ± 0.3% and TN by 4.19 ± 0.8%, and increased the C:N by 6.11 ± 0.9% across all the database. Specifically, the reduction of chemical nitrogen without adding organic nitrogen fertilizers would reduce SOC and TN by 3.83% and 11.46% respectively, while they increased SOC and TN by 4.92% and 8.33% respectively with organic fertilizers supplement, suggesting that organic fertilizers could cover the loss of SOC, TN induced by chemical nitrogen fertilizers reduction. Medium magnitude (20-30%) of chemical nitrogen fertilizers reduction enhanced SOC by 6.9%, while high magnitude (≧30%) and total (100%) of chemical nitrogen fertilizers reduction significantly decreased SOC by 3.10% and 7.26% respectively. Moreover, SOC showed a negative response to nitrogen fertilizers reduction at short-term duration (1-2 years), while the results converted under medium-long-termThis system analysis fills the gap on the effects of fertilizer reduction on soil organic carbon and nitrogen at the national scale, and provides technical foundation for the action of reducing fertilizer application while increase efficiency.

Directional sweat transport of monolayered cotton-fabrics fabricated through femtosecond-laser induced hydrophilization for personal moisture and thermal management.

Personal moisture and thermal management fabrics that can facilitate sweat removal and regulating skin temperature are highly desired for improving human comfort and performance. Here, we demonstrate a hydrophobic/superhydrophilic Janus cotton-fabric through femtosecond-laser-induced hydrophilization. The engineering Janus cotton-fabric can unidirectionally transport human sweat spontaneously. More importantly, the Janus fabrics can maintain human body temperature 2-3 °C lower than the conventional cotton fabrics, implying the cooling effect in thermal environment. In addition, the Janus fabric has lower wet skin adhesion in comparison with a conventional hydrophilic cotton fabric. The water vapor transmission rate (WVTR) of a Janus fabric is comparable to the traditional hydrophilic cotton fabrics. Overall, the successful creation of the Janus fabrics provides new insights for the development of moisture-wicking/thermal-management fabrics for satisfying the growing demand of personal comfort.

Soil bacterial community and metabolism showed a more sensitive response to PBAT biodegradable mulch residues than that of LDPE mulch residues.

Biodegradable mulch film (BDM) is considered as an environmentally sustainable alternative to low density polyethylene (LDPE) mulch film. However, the low degradation rate of BDM resulted in residues in soil after service period which were similar to LDPE mulch film. Distinguishing the differential responses of crop growth, soil bacteria and metabolism to residues of BDM and LDPE mulch films is favourable for comparing the environmental toxicities of the two materials. The results indicated that emergence rate and yield of Chinese cabbage (Brassica campestris L. ssp. chinensis Makino) were significantly inhibited by two types mulch residues. BDM residues significantly decreased bacterial diversity by 1.2-2.3% through the enrichment of dominant phyla and inhibition of inferior phyla, while LDPE mulch residues not. The effects of BDM residues on soil metabolite spectrum were stronger than LDPE mulch residues with significant increase (3.9% 5.8%) in the abundance of total metabolites. Besides the pathways of metabolism, organismal systems, environmental information processing influenced by LDPE mulch resides, differential pathways including human diseases and cellular processes were also determined in soil with BDM residues. According to all the results of the present study, prior to the promotion of BDM, its influences on soil safety must be carefully investigated through critical and systematic research.

A Biocompatible Vibration-Actuated Omni-Droplets Rectifier with Large Volume Range Fabricated by Femtosecond Laser.

High-performance droplet transport is crucial for diverse applications including biomedical detection, chemical micro-reaction, and droplet microfluidics. Despite extensive progress, traditional passive and active strategies are restricted to limited liquid types, small droplet volume ranges, and poor biocompatibilities. Moreover, more challenges occur for biological fluids due to large viscosity and low surface tension. Here, a vibration-actuated omni-droplets rectifier (VAODR) consisting of slippery ratchet arrays fabricated by femtosecond laser and vibration platforms is reported. Through the relative competition between the asymmetric adhesive resistance originating from the lubricant meniscus on the VAODR and the periodic inertial driving force originating from isotropic vibration, the fast (up to ≈60 mm s-1 ), programmable, and robust transport of droplets is achieved for a large volume range (0.05-2000 µL, Vmax /Vmin  ≈ 40 000) and in various transport modes including transport of liquid slugs in tubes, programmable and sequential transport, and bidirectional transport. This VAODR is general to a high diversity of biological and medical fluids, and thus can be used for biomedical detection including ABO blood-group tests and anticancer drugs screening. These strategies provide a complementary and promising platform for maneuvering omni-droplets that are fundamental to biomedical applications and other high-throughput omni-droplet operation fields.

Biomimetic Mechanoswitchable Interfaces for High-Performance Spatial Gas Bubble Maneuvering.

The on-demand manipulation of gas bubbles in aqueous ambient environments is fundamental to many fields such as microfluidics and biochemical microanalysis. However, most bubble manipulation strategies are limited to restricted locomotion on the confined surfaces without spatial convenience of transport. Herein, we report a kind of biomimetic bubble manipulator with mechanoswitchable interfaces (MSIs), featuring the advantages of parallel bubble control and spatial maneuvering flexibility. By the synergic action between Janus aluminum membrane and superaerophilic microfiber array, the gas-MSI interfacial adhesion can be reversibly switched to achieve capturing/releasing underwater bubbles. Moreover, the adhesion force of MSI can be readily tuned by diverse experimental parameters including surface roughness, fiber number, diameter, and spacing of the neighboring microfibers, which are further systematically investigated. Relying on this mobile platform, we demonstrate a series of powerful applications including bubble parallel control, bubble array regrouping, arbitrary bubble transport and even manipulating underwater solids through bubbles, which are otherwise challenging for conventional approaches. We envision that this versatile platform will bring new insights into potential applications, such as cross-species sample control and handheld gas microsyringe.

Magnetism-Actuated Superhydrophobic Flexible Microclaw: From Spatial Microdroplet Maneuvering to Cross-Species Control.

The flexible maneuvering of microliter liquid droplets is significant in both fundamental science and practical applications. However, most current strategies are limited to the rigid locomotion on confined geographies platforms, which greatly hinder their practical uses. Here, we propose a magnetism-actuated superhydrophobic flexible microclaw (MSFM) with hierarchical structures for water droplet manipulation. By virtue of precise femtosecond laser patterning on magnetism-responsive poly(dimethylsiloxane) (PDMS) films doped with carbonyl iron powder, this MSFM without chemical contamination exhibits powerful spatial droplet maneuvering advantages with fast response (<100 ms) and lossless water transport (∼50 cycles) in air. We further performed quantitative analysis of diverse experimental parameters including petal number, length, width, and iron element proportion in MSFM impacting the applicable maneuvering volumes. By coupling the advantages of spatial maneuverability and fast response into this versatile platform, typical unique applications are demonstrated such as programmable coalescence of droplets, collecting debris via droplets, tiny solid manipulation in aqueous severe environments, and harmless living creature control. We envision that this versatile MSFM should provide great potential for applications in microfluidics and cross-species robotics.

Hierarchical Hydrophilic/Hydrophobic/Bumpy Janus Membrane Fabricated by Femtosecond Laser Ablation for Highly Efficient Fog Harvesting.

The shortage of freshwater is threatening sustainable economic development and ecological security worldwide. Janus membrane, as a highly efficient method to collect the invisible fog water in the wet environment, is still hindered by some inherent limitations: (1) poor condensation of fog droplets on the superhydrophobic side due to the ultralow adhesive force of droplets with substrate and (2) insufficient detachment of droplets from the superhydrophilic side in time, which hampers the continuous water transport in the micropores. Herein, inspired by the desert beetle's back with alternating hydrophobic/hydrophilic bumps and the cactus thorn with an asymmetric geometry, we design and fabricate a kind of hierarchical hydrophilic/hydrophobic/bumpy Janus (HHHBJ) membrane by femtosecond laser ablation on an aluminum membrane to achieve the self-driven fog collection, which achieves over 250% enhancement in the water collection efficiency over the conventional Janus membrane. Even when the mist flow is applied to the surface at an incident angle of 45°, the collection efficiency increases by 600%. The mechanism of the HHHBJ film with excellent fog collection efficiency is mainly related to the continuous efficient fog condensation on the top surface and droplet removal on the bottom surface in time. We believe the proposed multi-bioinspired HHHBJ film with droplet self-driven collection ability provides insights to conceive and construct a highly efficient fog collection system in broad fields.

Sucrose Utilization for Improved Crop Yields: A Review Article.

Photosynthetic carbon converted to sucrose is vital for plant growth. Sucrose acts as a signaling molecule and a primary energy source that coordinates the source and sink development. Alteration in source-sink balance halts the physiological and developmental processes of plants, since plant growth is mostly triggered when the primary assimilates in the source leaf balance with the metabolic needs of the heterotrophic sinks. To measure up with the sink organ's metabolic needs, the improvement of photosynthetic carbon to synthesis sucrose, its remobilization, and utilization at the sink level becomes imperative. However, environmental cues that influence sucrose balance within these plant organs, limiting positive yield prospects, have also been a rising issue over the past few decades. Thus, this review discusses strategies to improve photosynthetic carbon assimilation, the pathways actively involved in the transport of sucrose from source to sink organs, and their utilization at the sink organ. We further emphasize the impact of various environmental cues on sucrose transport and utilization, and the strategic yield improvement approaches under such conditions.

High-Performance Unidirectional Manipulation of Microdroplets by Horizontal Vibration on Femtosecond Laser-Induced Slant Microwall Arrays.

The high-performance unidirectional manipulation of microdroplets is crucial for many vital applications including water collection and bioanalysis. Among several actuation methods (e.g., electric, magnetic, light, and thermal actuation), mechanical vibration is pollution-free and biocompatible. However, it suffers from limited droplet movement mode, small volume range (VMax /VMin  < 3), and low transport velocity (≤11.5 mm s-1 ) because the droplet motion is a sliding state caused by the vertical vibration on the asymmetric hydrophobic microstructures. Here, an alternative strategy is proposed-horizontal vibration for multimode (rolling, bouncing/reverse bouncing, converging/diffusing, climbing, 90o turning, and sequential transport), large-volume-range (VMax /VMin  ≈ 100), and high-speed (≈22.86 mm s-1 ) unidirectional microdroplet manipulation, which is ascribed to the rolling state on superhydrophobic slant microwall arrays (SMWAs) fabricated by the one-step femtosecond laser oblique ablation. The unidirectional transport mechanism relies on the variance of viscous resistance induced by the difference of contact area between the microdroplet and the slant microwalls. Furthermore, a circular, curved, and "L"-shaped SMWA is designed and fabricated for droplet motion with particular paths. Finally, sequential transport of large-volume-range droplets and chemical mixing microreaction of water-based droplets are demonstrated on the SMWA, which demonstrates the great potential in the field of microdroplet manipulation.

In Situ Reversible Tuning from Pinned to Roll-Down Superhydrophobic States on a Thermal-Responsive Shape Memory Polymer by a Silver Nanowire Film.

Shape memory polymer (SMP) surfaces with tunable wettability have attracted extensive attention due to their widespread applications. However, there have been rare reports on in situ tuning wettability with SMP materials. In this paper, we reported a kind of distinct superhydrophobic SMP microconed surface on the silver nanowire (AgNW) film to achieve in situ reversible transition between pinned and roll-down states. The mechanism is taking advantage of the in situ heating functionality of the silver nanowire film by voltage, which provides the transition energy for SMP to achieve the fixation and recovery of temporary shape. It is noteworthy that the reversible transition could be repeated many times (>100 cycles), and we quantitatively investigate the shape memory ability of microcones with varied height and space under different applied voltages. These results show that the tilted microcones could recover its original upright state under a small voltage (4-11 V) in a short time, and the shortest recovery time is about 0.5 min under an applied voltage of ∼10 V. Finally, we utilize SMP microcone arrays with tunable wettability to realize lossless droplet transportation, and the tilted microconed surface also achieves liquid unidirectional transport due to its anisotropic water adhesion force. The robust microconed SMP surface with reversible morphology transitions will have far-ranging applications including droplet manipulation, reprogrammable fog harvesting, and so on.

Adjusting cotton planting density under the climatic conditions of Henan Province, China.

The growth and development of cotton are closely related to climatic variables such as temperature and solar radiation. Adjusting planting density is one of the most effective measures for maximizing cotton yield under certain climatic conditions. The objectives of this study were (1) to determine the optimum planting density and the corresponding leaf area index (LAI) and yield under the climatic conditions of Henan Province, China, and (2) to learn how climatic conditions influence cotton growth, yield, and yield components. A three-year (2013-2015) field experiment was conducted in Anyang, Henan Province, using cultivar SCRC28 across six planting density treatments: 15,000, 33,000, 51,000, 69,000, 87,000, and 105,000 plants ha-1. The data showed that the yield attributes, including seed cotton yield, lint yield, dry matter accumulation, and the LAI, increased as planting density increased. Consequently, the treatment of the maximum density with 105,000 plants ha-1 was the highest-yielding over three years, with the LAIs averaged across the three years being 0.37 at the bud stage, 2.36 at the flower and boll-forming stage, and 1.37 at the boll-opening stage. Furthermore, the correlation between the cotton yield attributes and meteorological conditions indicated that light interception (LI) and the diurnal temperature range were the climatic factors that most strongly influenced cotton seed yield. Moreover, the influence of the number of growing degree days (GDD) on cotton was different at different growth stages. These observations will be useful for determining best management practices for cotton production under the climatic conditions of Henan Province, China.