Ethylene Concentration Research Articles

Basis for high-affinity ethylene binding by the ethylene receptor ETR1 of Arabidopsis

The gaseous hormone ethylene is perceived in plants by membrane-bound receptors, the best studied of these being ETR1 from Arabidopsis. Ethylene receptors can mediate a response to ethylene concentrations at less than one part per billion; however, the mechanistic basis for such high-affinity ligand binding has remained elusive. Here we identify an Asp residue within the ETR1 transmembrane domain that plays a critical role in ethylene binding. Site-directed mutation of the Asp to Asn results in a functional receptor that has a reduced affinity for ethylene, but still mediates ethylene responses in planta. The Asp residue is highly conserved among ethylene receptor-like proteins in plants and bacteria, but Asn variants exist, pointing to the physiological relevance of modulating ethylene-binding kinetics. Our results also support a bifunctional role for the Asp residue in forming a polar bridge to a conserved Lys residue in the receptor to mediate changes in signaling output. We propose a new structural model for the mechanism of ethylene binding and signal transduction, one with similarities to that found in a mammalian olfactory receptor.

Transcriptomic analysis of Cucumis sativus uncovers putative genes related to hormone signaling under low temperature (LT) and high humidity (HH) stress

Climate change has caused changes in environmental conditions, leading to both low temperature (LT) and high humidity (HH) stress on crops worldwide. Therefore, there is a growing need to enhance our understanding of the physiological and molecular mechanisms underlying LT and HH stress tolerance in cucumbers, given the significance of climate change. The findings of this study offer a comprehensive understanding of how the transcriptome and hormone profiles of cucumbers respond to LT and HH stress. In this study, cucumber seedlings were subjected to LT and HH stress (9/5 °C day/night temperature, 95% humidity) as well as control (CK) conditions (25/18 °C day/night temperature, 80% humidity) for 24, 48, and 72 h. It was observed that the LT and HH stress caused severe damage to the morphometric traits of the plants compared to the control treatment. The concentrations of phytohormones IAA, ethylene, and GA were lower, while ABA and JA were higher during LT and HH stress at most time points. To gain insights into the molecular mechanisms underlying this stress response, RNA-sequencing was performed. The analysis revealed a total of 10,459 differentially expressed genes (DEGs) with annotated pathways. These pathways included plant hormone signal transduction, protein processing in the endoplasmic reticulum, MAPK signaling pathway, carbon fixation in photosynthetic organisms, and glycerolipid metabolism. Furthermore, 123 DEGs associated with hormone signaling pathways were identified, and their responses to LT and HH stress were thoroughly discussed. Overall, this study sheds light on the LT and HH tolerance mechanisms in cucumbers, particularly focusing on the genes involved in the LT and HH response and the signaling pathways of endogenous phytohormones.

Investigation on the Effect of Charge Injection from Non-Thermal Plasma on Soot Formation in Laminar Coflow Diffusion Flame

ABSTRACT A novel, modified coflow burner was developed to study the effect of charge injection from a non-thermal plasma into three helium-diluted laminar coflow diffusion ethylene flames. The frequency of the high voltage (HV) signal was varied to control the ion concentration (charge) injected into the flames. Optical emission spectroscopy was used to characterize the non-thermal plasma while a bias plate methodology was used to gauge the relative amount of charge generated. For different HV signal frequencies, the laser-induced fluorescence of OH, chemiluminescence of CH*, and laser-induced incandescence of soot in flames were measured. The OH and CH* measurements showed that the flames retained the classic flame shape with charge injection. Significant soot reduction was observed at low HV signal frequencies, corresponding to an increase in charge injection. Notably, at low HV signal frequency, soot reduction in highly concentrated (60%) ethylene flame is three times lower than the less concentrated (32%) ethylene flame. This can be attributed to the decrease in the injected charge to soot precursor concentration ratio when the concentration of ethylene in the flame is increased. These results demonstrate that the current system is a promising candidate for studying the charge effect from non-thermal plasma on soot formation in laminar coflow diffusion flames.

1-MCP prevents ultrastructural changes in the organelles of Dendrobium petals that are induced by exogenous ethylene

Ethylene is a plant hormone that causes flower senescence. Dendrobium flowers are sensitive to ethylene and ethylene can induce premature senescence depending on the cultivar and the ethylene concentration. Dendrobium ‘Lucky Duan’ is one of the most sensitive cultivars to ethylene exposure. Open florets of ‘Lucky Duan’ were subjected to ethylene, 1-MCP, or 1-MCP plus ethylene treatments and compared with an untreated control. Ethylene induced earlier development of color fading, drooping and venation in petals, whereas 1-MCP pre-treatment counteracted these changes. Under light microscopy, epidermal cells and mesophyll parenchyma tissue around the vascular bundles of petals treated with ethylene showed collapsed cells whereas 1-MCP pre-treatment counteracted this collapse. An scanning electron microscopy (SEM) study confirmed clearly that ethylene treatment caused the collapse of mesophyll parenchyma tissue around vascular bundles. Ultrastructural changes were also studied using transmission electron microscopy (TEM) and showed that ethylene treatment induced morphological changes in conjunction with disorganization of the plasma membrane, the nuclei, chromatin, the nucleoli, myelin bodies, multivesicular bodies, and mitochondria including changes in size and number, breakages of membranes, enlargement of intercellular spaces and disintegration. 1-MCP pre-treatment was observed to counter these changes that were induced by ethylene. The role of ethylene-induced ultrastructural changes in the different organelles was apparently associated with membrane damage.

Effect of applications of 1-MCP and ethylene on the ripening and degreening process of banana fruits cv. Barranquillo

The banana cv. Barranquillo (Musa acuminata, AAA, ‘Gros Michel’) is a highly desired fruit because of its productive potential and organoleptic quality but various aspects of the ripening process are unknown. The objective of this research was to evaluate the effect of applications of 1-MCP and ethylene on the ripening and degreening process. Two experiments were carried out at room temperature with fruits harvested at commercial maturity. The first four treatments evaluated maturation: control, ethylene, 1-MCP, and 1-MCP + ethylene. In the second experiment, different concentrations of ethylene based on ethephon (0, 100, 500 and 1000 μL L-1) were evaluated. The fruits treated with 1-MCP decreased the ripening process, and 1-MCP was a good alternative for conserving the fruits; the ethylene had opposite results. The color index of the skin, weight loss, firmness, total soluble solids, and maturity ratio had changes associated with the presence of ethylene. In the second experiment, the ethylene applications between 100 and 500 μL L-1 sufficiently stimulated degreening but accelerated the ripening process.

Distribution characteristics and environmental effects of non-methane hydrocarbons in the East China Sea

Non-methane hydrocarbons (NMHCs) are important reactive compounds in the atmosphere which are crucial to the formation of ozone (O3) and secondary organic aerosol (SOA). In this study, the distribution characteristics, sea-to-air fluxes, and environmental effects of NMHCs were investigated in the East China Sea during spring and autumn. Affected by abundant nutrients and dissolved organic matter in the coastal area, NMHCs concentrations inshore were higher than those offshore. The mean concentrations of ethane, ethene, propane, propene, and isoprene were 5.1, 3.8, 6.0, 2.3, and 4.0 times higher in spring than autumn, respectively. In spring, the higher isoprene concentrations might have been due to the higher phytoplankton biomass and outbreak of dinoflagellates, while elevated concentrations of other NMHCs were primarily due to photochemical processes associated with high level of solar radiation. Influenced by terrestrial input and atmospheric chemical reactions, atmospheric concentrations of NMHCs were significantly higher in autumn than in spring. The mean concentrations of ethane, ethene, propane, propene, and isoprene were 221 ± 92.4, 182 ± 112, 198 ± 184, 46.4 ± 25.4, and 7.0 ± 2.9 pptv in spring, and 1090 ± 353, 655 ± 519, 701 ± 329, 476 ± 388, and 35.0 ± 23.2 pptv in autumn, respectively. The mean sea-to-air fluxes of the five NMHCs were 132 ± 126, 658 ± 591, 123 ± 128, 93.4 ± 89.0, and 120 ± 98.6 nmol m−2 d−1 in spring and 31.1 ± 25.9, 352 ± 212, 36.5 ± 40.5, 71.2 ± 43.9, and 78.6 ± 64.8 nmol m−2 d−1 in autumn, respectively. In addition, according to the environmental effects of NMHCs, alkenes exhibited higher atmospheric chemical reactivity and were the major contributors to O3 and SOA formation.

Harvest Maturity and Preharvest Aminoethoxyvinylglycine Treatment Effects on Cold-induced Ethylene Production of ‘Gala’ Apples

Cold storage is a commonly adopted technology to maintain quality and extend shelf life; however, depending on the cultivar, ethylene production can be enhanced by short-term cold treatments. In this study, index of absorbance difference (IAD) values, which reflect skin chlorophyll concentrations of cold-influenced ripening patterns, of ‘Gala’ apples were investigated. Fruit that were untreated or treated with aminoethoxyvinylglycine (AVG), which is a plant growth regulator that inhibits ethylene production of fruit, were harvested from a commercial orchard. Two IAD value categories 0.6 to 0.8 and 0.2 to 0.4 were chosen from a single harvest in 2019, whereas in 2020, the fruit in categories 0.6 to 0.8 and 0.2 to 0.4 were chosen for two harvests separated by 1 week, respectively. In 2019, only ethylene production was measured. In 2020, ethylene production, respiration, internal ethylene concentration (IEC), flesh firmness, 1-aminocyclopropane-1-carboxylate (ACC), and malonyl 1-aminocyclopropane-1-carboxylate (MACC) concentrations of fruit kept in air at 20 °C or stored at 0.5 °C for 21 days and then transferred to 20 °C were measured. The results were different from those described in the literature for cold-enhanced ethylene production of ‘Gala’ apples. Although ethylene production occurred without cold exposure of untreated fruit, exposure of fruit to 0.5 °C for 21 days resulted in more rapid and higher ethylene production rates and IEC than for fruit kept at only 20 °C. Ethylene production was suppressed by the preharvest AVG treatment, especially in 2020. The rates of respiration and softening of non-AVG treated fruit were enhanced by cold treatment. The effects of cold treatment were more significant for less mature fruit as indicated by higher IAD values.

Biodiversity and Functional Attributes of Rhizospheric Microbiomes: Potential Tools for Sustainable Agriculture

The quest for increasing agricultural yield due to increasing population pressure and demands for healthy food has inevitably led to the indiscriminate use of chemical fertilizers. On the contrary, the exposure of the crops to abiotic stress and biotic stress interferes with crop growth further hindering the productivity. Sustainable agricultural practices are of major importance to enhance production and feed the rising population. The use of plant growth promoting (PGP) rhizospheric microbes is emerging as an efficient approach to ameliorate global dependence on chemicals, improve stress tolerance of plants, boost up growth and ensure food security. Rhizosphere associated microbiomes promote the growth by enhancing the uptake of the nutrients, producing plant growth regulators, iron chelating complexes, shaping the root system under stress conditions and decreasing the levels of inhibitory ethylene concentrations and protecting plants from oxidative stress. Plant growth-promoting rhizospheric microbes belong to diverse range of genera including Acinetobacter, Achromobacter, Aspergillus, Bacillus, Burkholderia, Flavobacterium, Klebsiella, Micrococcus, Penicillium, Pseudomonas, Serratia and Trichoderma. Plant growth promoting microbes are an interesting aspect of research for scientific community and a number of formulations of beneficial microbes are also commercially available. Thus, recent progress in our understanding on rhizospheric microbiomes along with their major roles and mechanisms of action under natural and stressful conditions should facilitate their application as a reliable component in the management of sustainable agricultural system. This review highlights the diversity of plant growth promoting rhizospheric microbes, their mechanisms of plant growth promotion, their role under biotic and abiotic stress and status of biofertilizers. The article further focuses on the role of omics approaches in plant growth promoting rhizospheric microbes and draft genome of PGP microbes.

Effect of Nanoparticles and Organic Extract Preservatives on Vase Life of Cut Flowers: A Review

Cut flowers are used to express appreciation, affection and express emotions on various special occasions. The international trade in cut flowers has expanded in recent years and is expected to grow with the promotion and use of horticultural plants for their therapeutic benefits. Vase life is the period during which a cut flower maintains its appearance in the vase. This is a crucial factor in determining which plant species are ideal for use in floristry, with long vase life plants being considerably more desirable than short vase life plants. Chemical treatments that extend the life of vases are a major part of floristry. Adding sugars to a vase solution with cut flowers is known to delay aging and extend the life of the vase. Nano-sensors could therefore also help to extend the life of vases with cut flowers and thus enable the monitoring of ethylene concentrations in the warehouses of large growers and wholesalers. In floriculture, nanotechnology has increased yield to potential market value, particularly for essential micronutrients essential for host defence.

Proteomic changes in association with storage quality of ‘Honeycrisp’ apples after pre and postharvest treatment of 1-MCP

1-Methylcyclopropene (1-MCP) is a well-known ethylene action inhibitor that has been applied to fruit after harvest to maintain fruit quality and extend storage life. Recently, the preharvest application of 1-MCP in a sprayable form has been developed and has demonstrated some beneficial effects to prolong harvest window and improve fruit quality. To gain understanding of molecular mechanisms for 1-MCP treatment, as both pre- and postharvest applications on apples, we conducted a quantitative proteomic experiment employing stable isotope labeling by peptide dimethylation on ‘Honeycrisp’ apples to reveal the significantly changed protein abundance in relationship to fruit quality after preharvest 1-MCP (Harvista™), postharvest 1-MCP treatments as well as their combination. We revealed the treatment affected fruit internal ethylene concentration, fruit quality indices and storage disorders incidence after 7 months of storage at 3 °C. Our quantitative proteomic study identified and quantified more than 600 proteins. Among the identified proteins, 312 proteins were found in common from all treatments, while 141 proteins abundance were changed with regards to preharvest, postharvest and the combination treatments of 1-MCP. We identified a few proteins that were only shown as result of preharvest 1-MCP treatment, while postharvest 1-MCP and in combination with preharvest treatment led to larger number proteins with reduced abundance. These results revealed and confirmed that postharvest 1-MCP and in combination with preharvest 1-MCP treatment affected ethylene biosynthesis, stress resistance, amino acid biosynthesis, antioxidant and redox system metabolisms. Potential metabolic changes resulting from 1-MCP treatment were found, and the efficacy of preharvest 1-MCP treatment was also discussed.

The Plasma Ozonizer System for Mangosteen Storage Container to Preserve the Quality of Mangosteen

This research aims to produce ozone using a dielectric barrier discharge to extend the shelf life and preserve the quality of mangosteen. The optimum condition of this system was a minimum breakdown voltage of about 6 kVp-p, a resonance frequency of 224 kHz, and an oxygen flow rate of 2 L/min. The findings demonstrate that the maximal ethylene concentration value of treated fruit with ozone from oxygen flow rates 2 L/min lower than untreated fruit was approximately 11-fold. The L*, a*, b*, weight loss percentage, pericarp firmness value, and sensory evaluation were used to assess the quality of mangosteen. Compared to control fruit at 15 °C, fruit treated with ozone can have a prolonged shelf life of 9 days. Furthermore, assessing the quality and sensory score indicates that ozonation preserves the sensory quality of mangosteen. The weight loss percentage and pericarp firmness of fruit-treated ozone compared with the control were decreased by 3.34% and increased by 11.18 N, respectively. The sensory score of the fruit treated with ozone was higher than the control fruit, significantly different (p < 0.05).

Application of MgO-Titanomagnetite mixture in high-temperature catalytic pyrolysis of radiata pine

This study aimed to investigate the effect of MgO and titanomagnetite mixture on the high-temperature pyrolysis of radiata pine wood in a fluidised bed reactor at 850 °C. The catalytic performance of the MgO-titanomagnetite (MgO-TM) mixture was experimentally evaluated based on product distribution, gas composition, gas properties, and tar composition. The results revealed that addition of MgO-titanomagnetite resulted in a decrease in gas yield (67.2 wt.%) compared to addition of titanomagnetite (TM) alone (72.9 wt.%), but an improvement was found compared to addition of MgO alone (63.9 wt.%). The hydrogen concentration in the gas product was significantly enhanced (23.2 vol.%) compared to titanomagnetite alone (12.8 vol.%) or to non-catalytic (NC) pyrolysis (14.1 vol.%) but was similar to that with addition of MgO alone (22.6 vol.%). However, the addition of MgO and titanomagnetite mixture resulted in a reduction in CO concentration to 2.7 vol.% in the gas product whereas increased the CO2 and light olefins formation. It was also found that the addition of the MgO and titanomagnetite mixture significantly increased the total concentration of ethylene and propylene (18.3 vol.%) compared to addition of titanomagnetite (5.8 vol.%), MgO (9.0 vol.%), or non-catalytic pyrolysis (12.0 vol.%). The lower heating value of the gas product and the H2 to CO ratio (17.5 MJ/Nm3 and 8.7) were also improved with addition of the MgO-titanomagnetite mixture. These findings demonstrate that application of physically mixed MgO and titanomagnetite as catalyst is a promising method for converting biomass into a H2-rich gas product via high-temperature pyrolysis. This study offers a useful reference for the development of novel catalytic systems for biomass conversion.Graphical

Ethylene concentration inside tomato packages with a commercial ethylene scavenger

Ethylene concentration inside tomato packages with a commercial ethylene scavenger

Flower development and sexual dimorphism in Vernicia montana

The mu oil tree (Vernicia montana Lour.) is a dioecious species, but the genetic mechanisms underlying its phenotypic sexual dimorphism are unclear. In this study, we determined two pivotal phases of sex differentiation of mu oil tree via morphological and histological analyses of unisexual flowers: (I) differentiation of male or female primordia to produce staminate flowers (SFs) or transient hermaphrodite flowers (HFs), and (II) complete abortion of stamens in transient HFs to generate pistillate flowers (PFs). A total of 1621 sex-biased genes were identified by comparative transcriptome analysis which exhibited elevated rates of protein evolution than unbiased genes. The female-biased genes were enriched in the production of defense compounds while male-biased genes were focused on the production of viable pollens. Transcriptome-based analysis revealed that the differentially expressed genes (DEGs) between PFs and SFs in phase I involved in abscisic acid (ABA), auxin (AUX), cytokinin (CK), ethylene (ET), and gibberellin (GA) biosynthesis and signaling showed higher expression levels in males than in females in general, whereas the DEGs involved in jasmonic acid (JA) and salicylic acid (SA) pathways displayed opposite expression patterns. Moreover, differentially expressed endogenous ABA, AUX, GAs, JA, and SA exhibited consistent biased expression patterns with the DEGs by UPLC-MS-based analysis. Exogenous application of an anti-ethylene plant growth regulator could promote the development of stamens in PFs and generated HFs. Comparative transcriptomic and hormonal analyses of PFs and SFs in phase II indicated an increase in ET concentration when abortion of stamens in PFs occurred. This study suggested that phytohormones play key roles in sex dimorphism and ET may determine the development of stamens in PFs of mu oil tree, which provides an insight into plant sex differentiation mechanisms.

Elevated Atmospheric Ethylene and High Temperature Independently Inhibit Fruit Set But Not Vegetative Growth in Tomato

Ethylene is an essential plant hormone at low concentrations. Concentrations in the field rarely exceed 5 nmol⋅mol−1 (0.005 ppm), but it can accumulate as a gas in closed, indoor environments. These elevated levels can reduce growth and yield. Temperature alters ethylene synthesis and has the potential to influence ethylene sensitivity of crop plants in sealed greenhouses and indoor environments. We studied ethylene sensitivity of tomatoes (Solanum lycopersicum L. cv. MicroTina) using a unique, 12-chamber system. Ethylene levels of 0, 20, and 40 nmol⋅mol−1 (parts per billion) were maintained throughout the life cycle, at an air temperature of 22 or 28 °C. Yield of red fruit was three times higher at 22 than at 28 °C. There was a steady decrease in yield with increasing ethylene concentration, but vegetative growth was reduced less than 10% in any treatment. The highest ethylene concentration reduced yield to 11% of the control at 22 °C and to 4% of the control at 28 °C; the intermediate ethylene level reduced yield to 51% of the control at 22 °C and 37% at 28 °C. Regardless of temperature, filtering of ethylene in indoor environments to below 20 nmol⋅mol−1 is necessary to achieve normal fruit set and yield in tomato.

Evaluating the Classification of Freeze-Dried Slices and Cubes of Red-Fleshed Apple Genotypes Using Image Textures, Color Parameters, and Machine Learning

Dried red-fleshed apples are considered a promising high-quality product from the functional foods category. The objective of this study was to compare the flesh features of freeze-dried red-fleshed apples belonging to the ‘Alex Red’, ‘Trinity’, ‘314’, and ‘602’ genotypes and indicate which parameters and shapes of dried samples are the most useful to distinguish apple genotypes. Apple samples were at the stage of harvest maturity. The average fruit weight, starch index, internal ethylene concentration, flesh firmness, total soluble sugar content, and titratable acidity were determined. One hundred apple slices with a thickness of 4 mm and one hundred cubes with dimensions of 1.5 cm × 1.5 cm × 1.5 cm of each genotype were subjected to freeze-drying. For each apple sample (slice or cube), 2172 image texture parameters were extracted from images in 12 color channels, and color parameters L*, a*, and b* were determined. The classification models were developed based on a set of selected image textures and a set of combined selected image textures and color parameters of freeze-dried apple slices and cubes using various traditional machine-learning algorithms. Models built based on selected textures of slice images in 11 selected color channels correctly classified freeze-dried red-fleshed apple genotypes with an overall accuracy reaching 90.25% and mean absolute error of 0.0545; by adding selected color parameters (L*, b*) to models, an increase in the overall accuracy to 91.25% and a decrease in the mean absolute error to 0.0486 were observed. The classification of apple cube images using models including selected texture parameters from images in 11 selected color channels was characterized by an overall accuracy of up to 74.74%; adding color parameters (L*, a*, b*) to models resulted in an increase in the overall accuracy to 80.50%. The greatest mixing of cases was observed between ‘Alex Red’ and ‘Trinity’ as well as ‘314’ and ‘602’ apple slices and cubes. The developed models can be used in practice to distinguish freeze-dried red-fleshed apples in a non-destructive and objective manner. It can avoid mixing samples belonging to different genotypes with different chemical properties. Further studies can focus on using deep learning in addition to traditional machine learning to build models to distinguish dried red-fleshed apple samples. Moreover, other drying techniques can be applied, and image texture parameters and color features can be used to predict the changes in flesh structure and estimate the chemical properties of dried samples.

Non-destructive determination of ripening in melon fruit using time-resolved spectroscopy

The aim of this work was to explore the feasibility of time-resolved reflectance spectroscopy (TRS) in determining the ripening degree and the quality of orange-fleshed melons. Sixty ‘Honey Moon’ melons were measured by TRS in the 540-1064 nm range and classified as less (LeM), medium (MeM), and more (MoM) mature according to increasing values of μa540. MoM fruit showed yellower peel color, slightly more orange pulp, higher juiciness and higher carotenoid contents than LeM ones. MoM fruit also showed higher internal ethylene concentration and lower firmness than LeM ones, even if the differences were not significant. The μa540 was positively related to internal ethylene, carotenoid accumulation, and juiciness, indicating that μa540 was linked to different ripening processes in melons. However, the relationship between μa540 and total carotenoid content was not as high as expected due to the low variability of pulp color and of carotenoid content. Changes in flesh color toward a more orange shade were accompanied by increased juiciness and ethylene production and by carotenoid accumulation, while changes in peel color were associated with changes in flesh firmness and juiciness. In conclusion, the absorption coefficient measured at 540 nm (μa540) by TRS could be used to sort melons in different ripening degrees; however, its applicability will need to be evaluated on a larger number of fruits and on other varieties.

Exogenous Ethylene Alleviates the Inhibition of Sorbus pohuashanensis Embryo Germination in a Saline-Alkali Environment (NaHCO3).

Saline-alkali stress is a major environmental stress affecting the growth and development of plants such as Sorbus pohuashanensis. Although ethylene plays a crucial role in plant response to saline-alkaline stress, its mechanism remains elusive. The mechanism of action of ethylene (ETH) may be related to the accumulation of hormones, reactive oxygen species (ROS), and reactive nitrogen species (RNS). Ethephon is the exogenous ethylene donor. Therefore, for the present study we initially used different concentrations of ethephon (ETH) to treat S. pohuashanensis embryos and identified the best treatment concentration and method to promote the release of dormancy and the germination of S. pohuashanensis embryos. We then analyzed the physiological indexes, including endogenous hormones, ROS, antioxidant components, and reactive nitrogen, in embryos and seedlings to elucidate the mechanism via which ETH manages stress. The analysis showed that 45 mg/L was the best concentration of ETH to relieve the embryo dormancy. ETH at this concentration improved the germination of S. pohuashanensis by 183.21% under saline-alkaline stress; it also improved the germination index and germination potential of the embryos. Further analysis revealed that ETH treatment increased the levels of 1-aminocyclopropane-1-carboxylic acid (ACC), gibberellin (GA), soluble protein, nitric oxide (NO), and glutathione (GSH); increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), nitrate reductase (NR), and nitric oxide synthase (NOS); and decreased the levels of abscisic acid (ABA), hydrogen peroxide (H2O2), superoxide anion, and malondialdehyde (MDA) of S. pohuashanensis under saline-alkali stress. These results indicate that ETH mitigates the inhibitory effects of saline-alkali stress and provides a theoretical basis by which to establish precise control techniques for the release of seed dormancy of tree species.

Effects of Polymerization Medium on Nascent UHMWPE Properties and Sintered Material Performance

High-performance and easy-processing UHMWPE products with less entanglement and small particle size are difficult to synthesize efficiently in the polymerization process. In this study, a mixture of heptane and light paraffin is proposed as the polymerization medium to control the concentration of ethylene in the slurry during polymerization. Influences of the mixture composition on the polymerization behavior of ethylene, the particle size and its distribution of nascent UHMWPE, and the initial entangled state of UHMWPE were explored. Experimental results showed that as the volume fraction of heptane decreased, the viscosity of the solvent mixture increased exponentially, and ethylene solubility as well as mass transfer coefficient of ethylene in solvent decreased, which greatly affected the ethylene polymerization rate. By adjusting the volume fraction of heptane in the polymerization medium, the particle size, initial entanglement state density, and molecular weight of nascent UHMWPE will be coordinately controlled. UHMWPE with smaller particle size, lower entanglement density, and higher molecular weight can be prepared using the conventional Ziegler–Natta catalyst and polymerization medium with a lower heptane content, and its sintered UHMWPE material shows good mechanical properties.

Ethylene concentration is influenced by polyamine addition during somatic organogenesis in lemon (Citrus limon)

Ethylene concentration is influenced by polyamine addition during somatic organogenesis in lemon (<i>Citrus limon)</i>