Ethylene (C2H4) is a gaseous plant hormone produced by higher and lower (green) plants and, when grown on appropriate substrates, also by fungi, yeasts and bacteria. Ethylene is involved in many developmental processes in plants and is biologically active in trace amounts (10 – 100 nl/I of air) that may be present in the outside air due to industrial air pollution(1). Fruit ripening and flower senescence especially, in a variety of commercially important crops, are dramatically stimulated by (...) class='Hi'>ethylene. Following characterization of the genes coding for the key enzymes in ethylene biosynthesis, i.e. ACC synthase and ACC oxidase, it has become clear that their expression is regulated in a complex manner involving developmental, hormonal and tissue‐specific factors. This was recently very elegantly demonstrated for the expression of ACC oxidase genes in developing petunia flowers by Tang et al.(2). The spatial and temporal expression patterns, especially in the reproductive organs, suggest a hitherto unknown role for ethylene in reproductive processes such as the self‐incompatible response and the secretion of cellular exudate by the stigma and nectary. (shrink)

Small gaseous molecules play important roles in biological signaling in both animal and plant physiology. The hydrocarbon gas ethylene has long been known to regulate diverse aspects of plant growth and development, including fruit ripening, leaf senescence and flower abscission. Recent progress has been made toward identifying components involved in ethylene signal transduction in the plant Arabidopsis thaliana. Ethylene is perceived by five receptors that have similarity to two‐component signaling proteins. The hydrophobic amino‐terminus of the receptors binds (...) ethylene, and mutations in this domain both prevent ethylene binding and confer ethylene insensitivity to the plant; the carboxyl‐terminal portion of the receptors has similarity to bacterial his tidine protein kinases. Genetic data suggest a model in which ethylene binding inhibits receptor signaling, yet precisely how these receptors function is unclear. Two of the receptors have been found to associate with a negative regulator of ethylene responses called CTR1, which appears to be a mitogen‐activated protein kinase (MAPK) kinase kinase. BioEssays 23:619–627, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

Volatile compounds, such as nitric oxide and ethylene gas, play a vital role as signaling molecules in organisms. Ethylene is a plant hormone that regulates a wide range of plant growth, development, and responses to stress and is perceived by a family of ethylene receptors that localize in the endoplasmic reticulum. Constitutive Triple Response 1 (CTR1), a Raf‐like protein kinase and a key negative regulator for ethylene responses, tethers to the ethylene receptors, but undergoes nuclear (...) translocation upon activation of ethylene signaling. This ER‐to‐nucleus trafficking transforms CTR1 into a positive regulator for ethylene responses, significantly enhancing stress resilience to drought and salinity. The nuclear trafficking of CTR1 demonstrates that the spatiotemporal control of ethylene signaling is essential for stress adaptation. Understanding the mechanisms governing the spatiotemporal control of ethylene signaling elements is crucial for unraveling the system‐level regulatory mechanisms that collectively fine‐tune ethylene responses to optimize plant growth, development, and stress adaptation. (shrink)

In this article, ethylene glycol + waterbased Maxwell nanofluid with radiation and Soret effects within two parallel plates has been investigated. The problem is formulated in the form of partial differential equations. The dimensionless governing equations for concentration, energy, and momentum are generalized by the fractional molecular diffusion, thermal flux, and shear stress defined by the Caputo–Fabrizio time fractional derivatives. The solutions of the problems are obtained via Laplace inversion numerical algorithm, namely, Stehfest’s. Nanoparticles of silver are suspended in (...) a mixture of EG + water to have a nanofluid. It is observed that the thermal conductivity of fluid is enhanced by increasing the values of time and volume fraction. The temperature and velocity of water-silver nanofluid are higher than those of ethylene glycol + water -silver nanofluid. The results are discussed at 2% of volume fraction. The results justified the thermo-physical characteristics of base fluids and nanoparticles shown in the tables. The effects of major physical parameters are illustrated graphically and discussed in detail. (shrink)

Over the years, ethylene-diamine-tetra-acetate (EDTA) has been widely used for many purposes. However, there are inadequate phytoassessment studies conducted using EDTA in Vetiver grass. Hence, this study evaluates the phytoassessment (growth performance, accumulation trends, and proficiency of metal uptake) of Vetiver grass, Vetiveria zizanioides (Linn.) Nash in both single and mixed heavy metal (Cd, Pb, Cu, and Zn)—disodium EDTA-enhanced contaminated soil. The plant growth, metal accumulation, and overall efficiency of metal uptake by different plant parts (lower root, upper root, (...) lower tiller, and upper tiller) were thoroughly examined. The relative growth performance, metal tolerance, and phytoassessment of heavy metal in roots and tillers of Vetiver grass were examined. Metals in plants were measured using the flame atomic absorption spectrometry (F-AAS) after acid digestion. The root-tiller (R/T) ratio, biological concentration factor (BCF), biological accumulation coefficient (BAC), tolerance index (TI), translocation factor (TF), and metal uptake efficacy were used to estimate the potential of metal accumulation and translocation in Vetiver grass. All accumulation of heavy metals were significantly higher (p < 0.05) in both lower and upper roots and tillers of Vetiver grass for Cd + Pb + Cu + Zn + EDTA treatments as compared with the control. The single Zn + EDTA treatment accumulated the highest overall total amount of Zn (8068 ± 407 mg/kg) while the highest accumulation for Cu (1977 ± 293 mg/kg) and Pb (1096 ± 75 mg/kg) were recorded in the mixed Cd + Pb + Cu + Zn + EDTA treatment, respectively. Generally, the overall heavy metal accumulation trends of Vetiver grass were in the order of Zn >>> Cu > Pb >> Cd for all treatments. Furthermore, both upper roots and tillers of Vetiver grass recorded high tendency of accumulation for appreciably greater amounts of all heavy metals, regardless of single and/or mixed metal treatments. Thus, Vetiver grass can be recommended as a potential phytoextractor for all types of heavy metals, whereby its tillers will act as the sink for heavy metal accumulation in the presence of EDTA for all treatments. (shrink)

In their environment, plants are continuously submitted to natural stimuli such as wind, rain, temperature changes, wounding, etc. These signals induce a cascade of events which lead to metabolic and morphogenetic responses. In this paper the different steps are described and discussed starting from the reception of the signal by a plant organ to the final morphogenetic response. In our laboratory two plants are studied: Bryonia dioica for which rubbing the internode results in reduced elongation and enhanced radial expansion and (...) Bidens pilosa for which the response occurs at distance, hence pricking the cotyledon of a plantlet induces the growth inhibition of both the hypocotyl and the axillary bud of the pricked cotyledon. Reception of the signal and transmission of the message. In Bryonia the signal is received by epidermal cells while in Bidens they are the cells adjacent to the midrib of the cotyledon which receive the mechanical signal. In both plants the message is transmitted via a wave of electric depolarization. This latter is composed of an action potential associated with a slow wave whose transmission rates are respectively 1cm s−1 and 1 mm s−1. Recent results have shown the involvement of Ca2+ in the triggering of the slow wave and the role of the H+ pump during the slow wave. Transient and fast biochemical responses. An entry of extraceilular Ca2+ into the cells and a transient increase in IP3 occur within seconds following the mechanical stimulus. At the same time, the membrane becomes more fluid, correlated with qualitative changes in phospholipids. The rapid increase in the concentration of peroxidated lipids may be correlated with ethylene biosynthesis which is stimulated after rubbing. Other parameters such as cytoplasmic pH, relative water content, hydric potential, membrane potential and modifications of K+, Mg2+-ATPase and Ca2+-ATPase activities, play a key role in the early responses induced by the traumatisms. Irreversible-biochemical responses. The mechanical stimulus performed on a Bryonia internode induces an acceleration of: i) enzymatic activities related to the lignification, ii) esterification of phenolic acids in the cell wall. Consequently the lignification process is accelerated. Storage of the information. After being received by the target cells the information can be stored during several days before being expressed. At the level of cotyledonary bud, the first message, previously stored, can be expressed or not by a second treatment. Bidens thus behaves as if it was able to “store” and to “retrieve” morphogenetic messages, using a sort of rudimentary memory. The nuclei of the bud cells of the pricked cotyledon show that these cells, initially in G2 phase, divide and then remain in the G1 phase. In Bryonia, calli derived from young stimulated internodes, keep thigmomorphogenetic characteristics during several weeks. In the last part of this paper the particularity of our plant model which permits a study of the transmission and storage of the message, is underlined. The links between the different steps induced by the stimulus are discussed. Special attention is devoted to second messengers and to the amplification of the message. (shrink)

Mr. Bernard was a homeless man, aged 58. His medical history revealed alcohol abuse, seizure disorder, and two suicide attempts. Brought to the emergency room at a local hospital after being found “semi-comatose,” his respiratory distress led to his being intubated and placed on a ventilator. The healthcare team suspected the patient ingested antifreeze. Transferred from that hospital to the intensive care unit of the university hospital, his diagnosis was “high osmolar gap with high-anion gap metabolic acidosis, most likely secondary (...) to ethylene glycol ingestion and renal insufficiency.”. (shrink)

Cyanolichens are symbiotic organisms involving cyanobacteria and fungi (bipartite) or with the addition of an algal partner (tripartite). Cyanolichens are known for their heightened susceptibility to environmental pollution. We focus here on the impacts on cyanolichens due to rising air pollution; we are especially interested in the role of sulfur dioxide on cyanolichen biology. Cyanolichens due to air pollution including sulfur dioxide exposure, show symptomatic changes including degradation of chlorophyll, lipid membrane peroxidation, decrease in ATP production, changes in respiration rate, (...) and alteration of endogenous auxins and ethylene production, although symptoms are known to vary with species and genotype. Sulfur dioxide has been shown to be damaging to photosynthesis but is relatively benign on nitrogen fixation which proposes as a hypothesis that the algal partner may be more in harm’s way than the cyanobiont. In fact, the Nostoc cyanobiont of sulfur dioxide-susceptible Lobaria pulmonaria carries a magnified set of sulfur (alkane sulfonate) metabolism genes capable of alkane sulfonate transport and assimilation, which were only unraveled by genome sequencing, a technology unavailable in the 1950–2000 epoch, where most physiology- based studies were performed. There is worldwide a growing corpus of evidence that sulfur has an important role to play in biological symbioses including rhizobia-legumes, mycorrhizae-roots and cyanobacteria-host plants. Furthermore, the fungal and algal partners of L. pulmonaria appear not to have the sulfonate transporter genes again providing the roles of ambient-sulfur (alkanesulfonate metabolism etc.) mediated functions primarily to the cyanobacterial partner. In conclusion, we have addressed here the role of the atmospheric pollutant sulfur dioxide to tripartite cyanolichen viability and suggest that the weaker link is likely to be the photosynthetic algal (chlorophyte) partner and not the nitrogen-fixing cyanobiont. (shrink)