Slippery hydrogel with desiccation-tolerant‘skin’for high-precision additive manufacturing

Hydrogels inevitably undergo dehydration,structural collapse,and shrinkage deformation due to the uninterrupted evaporation in the atmosphere,thereby losing their flexibility,slipperiness,and manufacturing precision.Here,we propose a novel bioinspired strategy to construct a spontaneously formed‘skin’on the slippery hydrogels by incorporating biological stress metabolites trehalose into the hydrogel network,which can generate robust hydrogen bonding interactions to restrain water evaporation.The contents of trehalose in hydrogel matrix can also regulate the desiccation-tolerance,mechanical properties,and lubricating performance of slippery hydrogels in a wide range.Combining vat photopolymerization three-dimensional printing and trehalose-modified slippery hydrogels enables to achieve the structural hydrogels with high resolution,shape fidelity,and sophisticated architectures,instead of structural collapse and shrinkage deformation caused by dehydration.And thus,this proposed functional hydrogel adapts to manufacture large-scale hydrogels with sophisticated architectures in a long-term process.As a proof-of-concept demonstration,a high-precision and sophisticated slippery hydrogel vascular phantom was easily fabricated to imitate guidewire intervention.Additionally,the proposed protocol is universally applicable to diverse types of hydrogel systems.This strategy opens up a versatile methodology to fabricate dry-resistant slippery hydrogel for functional structures and devices,expanding their high-precision processing and broad applications in the atmosphere.

Effect of high light and desiccation on photosystem Ⅱ in the seedlings and mature plants of tropical seagrass Enhalus acoroides during low tide

During low tide,the intertidal seagrass Enhalus acoroides is often exposed to high light and desiccation,which can seriously threaten its survival,at least partly by inhibiting photosystem Ⅱ(PSⅡ)activity.The response of leaves of E.acoroides to high light and desiccation was compared for seedlings and mature plants.Results show that the resistance of seedling and mature leaves to high light was quite similar,but to desiccation was very different.Seedling leaves were more sensitive to desiccation than the mature plant leaves,but had better water retention.The damage of desiccation to seedling leaves was mainly caused by dehydration,whereas that to mature plant leaves was caused by hypersaline toxicity.The recovery rate of PSⅡ of seedling leaves was significantly slower than that of the mature plants after the stresses disappeared,which may at least partly contribute to seedling mortality in the wild.In addition,compared to high light,desiccation seriously inhibited the recovery rate of PSⅡ activities even if the leaves became fully rehydrated to their normal relative water content(RWC)in the following re-immersion.Desiccation inhibited the recovery rate of RC/CS_(M)(reaction center per cross section(at t=t_(Fm)))to decrease the production of assimilatory power,which maybe the cause of the slower PSⅡ recovery in desiccation treatments.This study demonstrates that desiccation particularly coupling with high light have a very negative ef fect on the PSⅡ of E.acoroides during low tide and the sensitivity of seedlings and mature plants to desiccation is significantly different,which have important reference significance to choose an appropriate transplanting depth where seedlings and mature plants of E.acoroides not only receive sufficient light for growth,but also that minimize desiccation stress during low tide.

Desiccation Alters the Stability and Distribution of Pea Seed_borne Mosaic Virus in Pea (Pisum sativum) Cotyledon Cells

As a seed transmitted pathogen, pea seed_borne mosaic virus (PSbMV) not only replicates in embryonic cells but can also withstand seed desiccation. To understand the mechanism of PSbMV tolerance to seed desiccation, the authors compared the stability of viral coat protein (CP) and the distribution of viral particles in the cotyledon cells of pea (Pisum sativum L.) embryos collected before and after the dehydration process. Before dehydration, when the embryo was fresh and immature, degradation of CP was observed and a predominantly perinuclear distribution of viral particles in the cotyledon cells was evident. After dehydration, when the embryo was dry and mature, degradation of CP did not occur and the perinuclear viral distribution disappeared. Instead, aggregates containing PSbMV CP were found in the cytoplasm. Electron microscopy showed that these aggregates were composed of PSbMV particles. The formation of PSbMV particle aggregates is apparently triggered by seed dehydration and may be favorable to the virus survival in the desiccated embryonic cells.

Study on Desiccation and Collection Models for Banana Stems

In this study, 8 kinds of desiccation models and 3 kinds of collection models were studied for banana stems. The results showed that the crushing-com- pression-air drying processing model showed the best desiccation effect for banana stems. Under this desiccation model, the moisture content was reduced from 90.5% to 19.93% with weight reduced by 75.2%; after 3 to 6 months of storage, the mois- ture content was still remained within 17%-20%, and the volume was decreased to 30%-40% of the original volume of fresh banana stems. This desiccation model made banana stems basically meet the requirements by drying storage. The plant- cutting down-crushing-compression-transportation-desiccation-storage production model was initially developed for desiccation and collection of banana stems, which would lay a certain foundation for the utilization of banana stem resource by enterprises.

Electron paramagnetic resonance study of amphiphiles partitioning behavior in desiccation-tolerant moss during dehydration

Desiccation tolerance is a crucial characteristic for desert moss surviving in arid regions. Desiccation procedure always induces amphiphiles transferring from the polar cytoplasm into lipid bodies. The behavior of amphiphiles transferring can contribute to the enhancement of desiccation tolerance and the reduction of plasma membrane integrity simultaneously. The effects of amphiphiles partitioning into the lipid phase during water loss has been studied for pollen and seeds using electron paramagnetic resonance （EPR） spectroscopy. However, desiccation-tolerant high plants occur among mosses, several angiosperms and higher plants seeds or pollens. They have different strategies for survival in dehydration and rehydration. A desiccation-tolerant moss Tortula desertorurn was used to investigate the behaviors of amphiphilic molecules during drying by spin label technology. There are small amount of amphiphilic probes partitioning into membrane during moss leaves dehydration, comparing with that in higher plants. Cytoplasm viscosity changed from 1.14 into glass state only dehydration less than 60 min. Moss leaves lost plasma membrane integrity slightly,from 0.115 to 0.237, occurred simultaneously with amphiphiles partition. The results showed the more advantages of mosses than higher plants in adapting fast dehydration. We propose that EPR spin label is feasible for studying the amphiphiles partitioning mechanisms in membrane protection and damage for desiccation-tolerant mosses.

Rates of oxygen consumption and tolerance of hypoxia and desiccation in Chinese black sleeper(Bostrichthys sinensis)and mudskipper(Boleophthalmus pectinirostris)embryos

The rates of oxygen consumption, tolerance of hypoxia and desiccation of the Chinese black sleeper （ Bostrichthys sinensis） and mudskipper （Boleophthalmus pectinirostris） embryos were investigated. The pattern of oxygen consumption of the Chinese black sleeper embryos was similar to that of the mudskipper ones. The lowest rates of oxygen consumption [ （ 1.65 ±0. 66） nmol/ （ind. ·h） ] of the Chinese black sleeper embryos 16 h after fertilization and the lowest rates of oxygen consumption [ （0.79± 0.08 ）nmolf（ ind. · h） ] of the mudskipper embryos 6 h after fertilization were recorded, respectively. Then the rates of oxygen consumption of these two species embryos increased gradually until hatching [ （8.26 ± 1.70 ） nmolf（ ind.· h） in the Chinese black sleeper, （2.69 ± 0.23 ）nmolf（ ind. · h） in mudskipper]. After exposure to hypoxia water （0.16 mg/dm^3）, bradycardia of the embryos occurred in both the Chinese black sleeper and the mudskipper. However, the Chinese black sleeper embryos survived approximately 45 min longer than the mudskipper ones. After exposure to desiccation at a relative humidity of 58%, bradycardia of the embryos was observed in both the Chinese black sleeper and the mudskipper, and the Chinese black sleeper embryos lived approximately 9 min longer than the mudskipper ones.

Somatic embryogenesis and peroxidase activity of desiccation tol-erant mature somatic embryos of loblolly pine

White, translucent, glossy mucilaginous callus was initiated from the mature zygotic embryos explants on callus induction medium with 2,4-D, BA, and kinetin in the 3-9th week of culture. This type of callus induction occurred at a lower fre-quency with either a-naphthaleneacetic acid (NAA) or IBA (both 8 mg/L). White, translucent, glossy mucilaginous callus was embryogenic and mainly developed from the cotyledons of the mature zygotic embryo. Somatic embryos were formed on dif-ferentiation medium. Desiccation tolerance can be induced by culturing somatic embryos of loblolly pine (Pinus taeda L.) on medium supplemented with 50 mm abscisic acid (ABA) and/or 8.5% polyethylene glycol (PEG6000). Scanning electron micros-copy of desiccated somatic embryos showed that the size and external morphology of the desiccation tolerant somatic embryos recovered to the pre-desiccation state within 24-36 h, whereas the sensitive somatic embryos did not recover and remained shriveled, after the desiccated somatic embryos had been rehydrated. Peroxidase activity of desiccated somatic embryos in-creased sharply after 3 days of desiccation treatment, and desiccation tolerant somatic embryos had higher peroxidase activity compared to sensitive somatic embryos. Higher peroxidase activity of desiccation tolerant somatic embryos was possibly ad-vantage of catalyzing the reduction of H2O2 which was produced by drought stress, and protecting somatic embryos from oxida-tive damage.

Desiccation tolerance in bryophytes： the rehydration proteomes of Bryum argenteum provide insights into the resuscitation mechanism

Bryum argenteum Hedw. is a desiccation tolerant bryophyte and belongs to one of the most important components of the biological soil crusts （BSCs） found in the deserts of Central Asia. Limited information is available on rehydration-responsive proteins in desiccation tolerant plants. As a complement to our previous research analyzing the rehydration transcriptome, we present a parallel quantitative proteomic effort to study rehydration-responsive proteins. Bryophyte gametophores were desiccated （Dry） and rehydrated for 2 h （R2） and 24 h （R24）. Proteins from Dry, R2 and R24 gametophores were labeled by isobaric tags for relative and absolute quantitation （iTRAQ） to determine the relative abundance of rehydration-responsive proteins. A total of 5503 non-redundant protein sequences were identified and 4772 （86.7%） protein sequences were annotated using Gene Ontology （GO） terms and Pfam classifications. Upon rehydration 239 proteins were elevated and 461 proteins were reduced as compared to the desiccated protein sample. Differentially up-regulated proteins were classified into a number of categories including reactive oxygen species scavenging enzymes, detoxifying enzymes, Late Embryogenesis Abundant （LEA） proteins, heat shock proteins, proteasome components and proteases, and photosynthesis and translation related proteins. Furthermore, the results of the correlation between transcriptome and proteome revealed the discordant changes in the expression between protein and mRNA.

Effects of leachate infiltration and desiccation cracks on hydraulic conductivity of compacted clay

Both cracks in clay liner and the complex composition of landfill leachate might have effects on the hydraulic conductivity of a compacted clay liner. In this study, the hydraulic conductivities of natural clay and bentonite-modified clay with and without desiccation cracks were measured, respectively, using three types of liquids as permeating liquid： 2 500 mg/L acetic acid solution, 0.5 mol/L CaCl2 solution, and tap water. When tap water was adopted as the permeating liquid, desiccation cracks resulted in increases in the average value of hydraulic conductivity： a 25-fold increase for the natural clay and a 5.7-fold increase for the bentonite-modified clay. It was also found out that the strong selfhealing capability of bentonite helped to reduce the adverse impact of cracks on hydraulic performance. In contrast to tap water, simulated leachates（acetic acid and CaCl2 solutions） show no adverse effect on the hydraulic conductivities of natural and bentonite-modified clays. It is concluded that desiccation cracks and bentonite have more significant effects on hydraulic performance than simulated leachates.

Influence of Desiccation Time on Survival and Regeneration of Embryonic Axes of Groundnut (<i>Arachis hypogaea</i>L.) Immersed in Liquid Nitrogen

Cryopreservation, the storage of biological materials in liquid nitrogen (LN), is a useful method for long term conservation of plant germplasm. This study was carried out with the objective of establishing an efficient desiccation technique for successful cryopreservation and recovery of embryonic axes of groundnut. Embryonic axes of four groundnut (Arachis hypogaea L.) genotypes were evaluated. The excised embryonic axes were dehydrated by air current of a laminar air flow cabinet for different duration (0, 1, 2, 3, 4 & 5 hrs) before being plunged in LN (-196℃) and held for 1 hr. Samples were thawed in water bath at 40℃?for 2 min, thereafter cultured on MS medium supplemented with 15 mg/L BAP for recovery. Highest survival (96.67%-100%) and shoot formation (91.67%-96.67%) were obtained at an average moisture content of 17% after 4-5 hr desiccation. Among the genotypes evaluated, Samnut 22 and Samnut 23 recorded the highest survival and shoot formation. This technique therefore appears promising for cryopreservation of groundnut germplasm.

Desiccation versus Re-Flooding: Heavy Metals Mobilization—Part 1

From the restoration point of view, heavy metals distribution and seasonal variation were studied in the re-flooded marshes of the Mesopotamia, southern Iraq. As part of the ecological recovery assessment of these newly inundated marshes, it is important to investigate the extend impact of 13 years of desiccation after five years of inundation on the heavy metals mobilization from the marshland downstream into the Shatt Al-Arab River and examine whether these marshlands retain their role of acting as sink of metals. The result shows significant differences between the re-flooded marshes versus the reference marsh, which indicates that desiccation cased changes in environmental variables and divided the one homogeneous system of the Mesopotamia into separated systems. In addition, the special distribution of heavy metals show that Al-Hawizeh and Al-Hammar marshlands were efficient for metals reduction, especially for Ni, while the Central marshland has the major contribution as source to metals. As a conclusion, the recovery potential of three marshlands is strongly controlled by the hydrological status of the marshland and the degree of the desiccation impact. The environmental status of the semidried marshes, Al-Souda north and Um Al-Niaaj, as well as the completely Abu Zarag dried marsh are exhibiting a positive recovery degree than the other monitored marshes in the Mesopotamia in comparison to the reference marsh.

Ultrastructural analysis of the loss of desiccation tolerance in germinating Eremanthus erythropappus seeds

Eremanthus erythropappus(DC.)MacLeish is an important forest species native to the Brazilian savanna biome,an environment with well-defined rainy and dry seasons.Its seeds are desiccation tolerant,non-dormant and dispersed at the end of dry season.This exposes them to the first sporadic rains that can trigger germination but the subsequent dry days can compromise survival of the newly germinated seed.This study evaluates if the damages caused by drying of germinating E.erythropappus seeds,at the stage when they have lost desiccation tolerance,are lethal.The percentage of normal seedlings was evaluated when seeds with different imbibition times were dried to their initial water content and then pre-humidified and rehydrated.Desiccation tolerance was fully lost after 0.5 mm of hypocotyl-radicle protrusion(approximately 72 h)when the radicle had root hairs,a possible indicator of sensitivity to desiccation.Disintegration of cell contents and ultrastructural damage to the seeds subjected to drying were observed by electron scanning microscope.Root hairs disappeared after drying,reappearing after pre-humidification,possibly an attempt to increase the surface area of the radicle for water uptake.However,the hypocotylradicle axis became darkened,probably by antioxidant system failure,causing seed death.

Effect of Desiccation of Marine Environment on Beam Structure

This paper presents the study on the effect of desiccation for different part of offshore structure corresponding to the water level. A coupled elastoplastic damage model is proposed to describe the mechanical behavior of cement-based materials under external loading and desiccation, in which both the plastic and damage behaviors under multi-axial stress are considered in composition with the desiccation effect. The comparison between numerical simulation and experimental data indicates that the proposed model can well predict the mechanical characteristics of cement-based materials with different saturations. In addition, a series of small beams subjected to desiccation are further analyzed to reveal the response of structure in the drying process.

Effect of desiccation on regeneration frequency of green plantlets and some biochemical properties of calli of wild rice

Wild rice is an important resource of usefulgenes to rice breeders. However, low regener-ation frequency is an obstacle to use the valu-able genes. We used desiccation to improve theregeneration frequency and studied the bio-chemical changes of calli of wild rice after des-iccation.Materials used in this experiment werewild species O. rufipogon, O. meyeriana, O.alta, and O. brachyantha. Young panicles(0.1-0. 5 cm in length of the inflorescence)

Exploring an eco-friendly approach to improve soil tensile behavior and cracking resistance

Soil tensile strength is a critical parameter governing the initiation and propagation of tensile cracking.This study proposes an eco-friendly approach to improve the tensile behavior and crack resistance of clayey soils.To validate the feasibility and efficacy of the proposed approach,direct tensile tests were employed to determine the tensile strength of the compacted soil with different W-OH treatment concentrations and water contents.Desiccation tests were also performed to evaluate the effectiveness of W-OH treatment in enhancing soil tensile cracking resistance.During this period,the effects of W-OH treatment concentration and water content on tensile properties,soil suction and microstructure were investigated.The tensile tests reveal that W-OH treatment has a significant impact on the tensile strength and failure mode of the soil,which not only effectively enhances the tensile strength and failure displacement,but also changes the brittle failure behavior into a more ductile quasi-brittle failure behavior.The suction measurements and mercury intrusion porosimetry(MIP)tests show that W-OH treatment can slightly reduce soil suction by affecting skeleton structure and increasing macropores.Combined with the microstructural analysis,it becomes evident that the significant improvement in soil tensile behavior through W-OH treatment is mainly attributed to the W-OH gel's ability to provide additional binding force for bridging and encapsulating the soil particles.Moreover,desiccation tests demonstrate that W-OH treatment can significantly reduce or even inhibit the formation of soil tensile cracking.With the increase of W-OH treatment concentration,the surface crack ratio and total crack length are significantly reduced.This study enhances a fundamental understanding of eco-polymer impacts on soil mechanical properties and provides valuable insight into their potential application for improving soil crack resistance.

Protective mechanism of desiccation tolerance in Reaumuria soongorica: Leaf abscission and sucrose accumulation in the stem

Reaumuria soongorica (Pall.) Maxim., a perennial semi-shrub, is widely found in semi-arid areas in northwestern China and can survive severe desiccation of its vegetative organs. In order to study the protective mechanism of desiccation tolerance in R. soongorica, diurnal patterns of net photosynthetic rate (Pn), water use efficiency (WUE) and chlorophyll fluorescence parameters of Photosystem II (PSII), and sugar content in the source leaf and stem were investigated in 6-year-old plants during progressive soil drought imposed by the cessation of watering. The results showed that R. soongorica was char-acterized by very low leaf water potential, high WUE, photosynthesis and high accumulation of sucrose in the stem and leaf abscission under desiccation. The maximum Pn increased at first and then de-clined during drought, but intrinsic WUE increased remarkably in the morning with increasing drought stress. The maximal photochemical efficiency of PSII (Fv/Fm) and the quantum efficiency of noncyclic electric transport of PSII(ΦPSII) decreased significantly under water stress and exhibited an obvious phenomenon of photoinhibition at noon. Drought stressed plants maintained a higher capacity of dis-sipation of the excitation energy (measured as NPQ) with the increasing intensity of stress. Conditions of progressive drought promoted sucrose and starch accumulation in the stems but not in the leaves. However, when leaf water potential was less than –21.3 MPa, the plant leaves died and then abscised. But the stem photosynthesis remained and, afterward the plants entered the dormant state. Upon re-watering, the shoots reactivated and the plants developed new leaves. Therefore, R. soongorica has the ability to reduce water loss through leaf abscission and maintain the vigor of the stem cells to survive desiccation.

Effects of pre-harvest chemical application on rice desiccation and seed quality

Pre-harvest desiccation may increase the efficiency of seed production. Field studies were conducted to determine the effects of diquat, paraquat, and ethephon applications on grain moisture, grain weight, and seed ger- mination of hybrid rice Yanliangyou 88 （Oryza sativa ssp. indica） and conventional rice Wuyunjing 7 （Oryza sativa ssp. japonica）. In 2013, we tested 12 treatments applied at four weeks （Yanliangyou 88） and six weeks （Wuyunjing 7） after heading. Results showed that reductions in moisture content were significant two and four days after chemical ap- plication. Chemical applications had no adverse effects on lO00-grain weight, germination percentage, or germination index, but there were negative effects on the percentage of normal seedlings. Desiccation effects increased with increase in the period after application, while the effect of ethephon combined with diquat or paraquat on desiccation was limited compared with that of diquat or paraquat alone in a short period after application. In 2013, chemical ap- plications reduced the moisture content by from 0.5% to 6.4%, the germination percentage by from 0% to 3.3%, and the percentage of normal seedlings by from 13.3% to 100.0%. Among the treatments, diquat applied at 120 g/ha resulted in effective desiccation with fewer negative effects on grain weight and seed germination in 2013 and 2014. Therefore, diquat may have potential as a pre-harvest chemical desiccation treatment for rice. These results may provide a basis for developing and implementing protocols for large scale field trials.

Discrepancy in photosynthetic responses of the red alga Pyropia yezoensis to dehydration stresses under exposure to desiccation,high salinity,and high mannitol concentration

Macroalgae that inhabit intertidal zones are exposed to the air for several hours during low tide and must endure desiccation and high variations in temperature, light intensity, and salinity. Pyropia yezoensis (Rhodophyta, Bangiales), a typical intertidal red macroalga that is commercially cultivated in the northwestern Pacific Ocean, was investigated under different dehydration stresses of desiccation, high salinity, and high mannitol concentration. Using chlorophyll fluorescence imaging, photosynthetic activities of P. yezoensis thalli were analyzed using six parameters derived from quenching curves and rapid light curves. A distinct discrepancy was revealed in photosynthetic responses to different dehydration stresses. Dehydration caused by exposure to air resulted in rapid decreases in photosynthetic activities, which were always lower than two other stresses at the same water loss (WL) level. High salinity only reduced photosynthesis significantly at its maximum WL of 40% but maintained a relatively stable maximum quantum yield of photosystem II (PSII) (Fv/Fm). High mannitol concentration induced maximum WL of 20% for a longer time (60 min) than the other two treatments and caused no adverse influences on the six parameters at different WL except for a significant decrease in non-photochemical quenching (NPQ) at 20% WL. Illustrated by chlorophyll fluorescence images, severe spatial heterogeneities were induced by desiccation with lower values in the upper parts than the middle or basal parts of the thalli. The NPQ and rETRmax (maximum relative electron transport rate) demonstrated clear distinctions for evaluating photosynthetic responses, indicating their sensitivity and applicability. The findings of this study indicated that the natural dehydration of exposure to air results in stronger and more heterogeneous effects than those of high salinity or high mannitol concentration.

Effect of biochar type on infiltration,water retention and desiccation crack potential of a silty sand

Biochar is a carbon-rich material obtained after thermochemical conversion of biomass under no oxygen environment.The effect of biochar amendment on soil properties,such as water retention,infiltration and desiccation crack potential was studied in the recent years.However,the effect of biochar or feedstock type on these properties is not explicit.This study investigates the effect of two different(in terms of feedstock)types of biochar on the water retention,infiltration and desiccation crack-ing behavior of compacted silty sand.Water retention characteristics,infiltration rate and the progression of desiccation cracks were measured after compacting soil amended with 5-10%(w/w)biochar produced from water hyacinth(WHB)and mesquite.Measurements were also taken for an unpyrolyzed material coir pith(CP,sourced from coconut husk)-amended soil for comparing the results of biochar-amended soil.The results show that the amendment of 5%to 10%biochar increased the maximum water holding capacity(θs),air entry value(AEV)and water content at 1500 kPa(θ1500)of the soil,whereas decreased the infiltration rate and peak crack intensity factor(CIF)of the soil.Moreover,the application of CP increased the infiltration rate.The amendment of WHB showed the highest increment in AEV andθ1500 and the highest decrement in infiltration rate and CIF compared to the other amendments.Based on the results,it is advisable to use the WHB-amended soil in bioengineered structures that could promote the growth of vegetation by higher water retention and could reduce the potential of leachate formation by decreasing water infiltration and desiccation crack potential.

DESICCATION OF THE MIDDLE ORDOVICIAN EPEIRIC SEA IN NORTH CHINA

Ⅰ. INTRODUCTION The Middle Ordovician evaporites in North China have been commonly considered as distributing only in the central part of the epeiric sea. Their genesis has raised much controversy among sedimentologists. The purpose of this study is to simulate the distribution