Role of endogenous gibberellins in germination of melon (Cucumis melo) seeds

The effect of the plant growth retardants ancymidol. mefluidide and uniconazole on germination of two melon accessions differing in their ability to germinate at 14°C was examined. The accessions were the cold sensitive Noy Yizre'el and the cold tolerant Persia 202. The three growth retardants were able to delay the germination of intact Noy Yizre'el seeds, but did not affect that of intact Persia 202 seeds. On the other hand germination of decoated seeds of both accessions was unaffected by these inhibitors at normal oxygen concentration, but was inhibited at 5% oxygen. When gibberellin-like activity was measured by a dwarf rice biological assay following HPLC fractionation, it was found that seeds of Persia 202 contained much more gibberellin-like activity than Noy Yizre'el seeds. Among the extracted compounds several endogenous gibberellins were identified by combined gas chromatography-mass spectrometry (GC-MS). They included GA₄, GA₂₀, GA₁ and GA₃ in Noy Yizre'el and GA₃₄, GA₂₀, GA₁ and GA₈ in Persia 202. It is suggested that the better germination of intact Persia 202 seeds, compared to Noy Yizre'el seeds at low temperature and low oxygen concentration, is due to a higher endogenous level of GA and a better seed coat permeability to oxygen.     

Chemotaxonomic significance of the xanthomonadins,novel brominated aryl-polyene pigments produced by bacteria of the genus Xanthomonas

The cell pigments produced by strains of Xanthomonas spp. (including representatives of all five presently recognized taxospecies of these phytopathogenic bacteria) have been isolated as isobutyl esters, purified, and characterized in terms of electronic absorption, chromatographic and co-chromatographic, and mass spectrometric properties. This comparative examination reveals that these bacteria produce brominated aryl-polyene pigments which are given the trivial name xanthomonadins. The several xanthomonadins usually occur as mixtures which have been resolved by chromatography and sorted into several Pigment Groups, thus enabling a more rational approach in our on-going systematic study of their exact chemical structures and biosynthesis. From what is presently known, some of the xanthomonadins might differ from xanthomonadin I, the exact structure of which has previously been determined in material from Xanthomonas juglandis ICPB XJ103, by their being monobrominated (rather than dibrominated, as is xanthomonadin I), by their having the equivalent of one methyl group less than does xanthomonadin I, and/or in other ways. The pigments of Xanthomonas ampelina (a little known and possibly questionable member of this genus) seem somewhat different from the pigments of the other Xanthomonas spp. The ability to form these distinctive xanthomonadin pigments is a useful chemotaxonomic marker for the genus Xanthomonas, since such pigments are not known to be formed by taxonomically or ecologically adjacent bacteria. Sufficient characterization of this assemblage of xanthomonadin pigments is presented so that they can be isolated and identified routinely on the basis of the aforementioned properties.     

Quantitative changes in potassium,sodium, and calcium in the submaxillary salivary gland and blood serum of rats exposed to 2880-MHz microwave radiation

Na⁺, K⁺, and Ca²⁺ concentrations in the blood serum and submaxillary salivary gland (SSG) were investigated in adult, male rats exposed to 2880-MHz microwaves modulated with 1.5-μs pulses at a pulse repetition rate of 1000 Hz or in a hyperthermal environment. Rats were exposed, one at a time, for 30 min to microwaves producing a specific absorption rate (SAR) of: 4.2, 6.3,6.8,8.4, 10.8, or 12.6 W/kg, or were sham exposed under similar environmental conditions. In a second series, one group of rats was exposed singly for 15, 30, or 60 min to microwaves producing an SAR of 9.5 W/kg and other rats were exposed for similar periods at 40 °C; and 10 rats were sham exposed. Flame photometric analysis indicated that the thresholds of microwave radiation required to induce a change in Na⁺, K⁺, and Ca²⁺ concentrations in the salivary glands are 6.8, 6.8, and 6.3 W/kg, respectively. The directions of Na⁺, K⁺, and Ca²⁺ ion shifts in exposed rats' salivary glands are similar, whether affected by microwaves or hyperthermia. Greater changes in Na⁺ and K⁺ concentrations in SSG of rats exposed to microwaves for 15 and 30 min were found than in those exposed at 40 °C. On the other hand, exposure to hyperthermia at 40 °C or to microwaves for 1 h caused Na⁺ concentration to be increased by 68.7 and 59.5% and K⁺ concentration to be decreased by 29.6 and 21.7%, respectively.     

The manipulation of polar head group composition of phospholipids in the wheat Miranovskaja 808 affects frost tolerance

Caryopses of the frost-resistant cultivar of the wheat Triticum aestivum L., Miranovskaja 808, were germinated and grown in the presence of various concentrations of choline chloride. Changes in the composition of leaf total phospholipids and leaf total fatty acids at two extreme temperatures (25°C and 2°C) as well as changes in frost resistance were followed. A choline chloride concentration-dependent accumulation of phosphatidyl choline was observed in the leaves. Seedlings grown at 2°C accumulated more phosphatidyl choline at each choline chloride concentration than those grown at 25°C. There was an inverse relationship between the contents of phosphatidyl choline and phosphatidic acid in the leaves. Neither the temperature nor choline chloride seemed to affect fatty-acid composition. Modification of polar-head group composition of phospholipids affected frost tolerance: Seedlings grown in the presence of 15 mM choline chloride at 25°C exhibited a freezing resistance equal to that of hardened controls. The data indicate that the polar-head group composition of membrane phospholipids in plants can be easily manipulated and point to the importance of phosphatidyl choline in cold adaptation processes.     

Uncovering Atomic‐Scale Stability and Reactivity in Engineered Zinc Oxide Electrocatalysts for Controllable Syngas Production

In this study, scalable, flame spray synthesis is utilized to develop defective ZnO nanomaterials for the concurrent generation of H₂ and CO during electrochemical CO₂ reduction reactions (CO₂RR). The designed ZnO achieves an H₂/CO ratio of ≈1 with a large current density (j) of 40 mA cm^?2 during long‐term continuous reaction at a cell voltage of 2.6 V. Through in situ atomic pair distribution function analysis, the remarkable stability of these ZnO structures is explored, addressing the knowledge gap in understanding the dynamics of oxide catalysts during CO₂RR. Through optimization of synthesis conditions, ZnO facets are modulated which are shown to affect reaction selectivity, in agreement with theoretical calculations. These findings and insights on synthetic manipulation of active sites in defective metal‐oxides can be used as guidelines to develop active catalysts for syngas production for renewable power‐to‐X to generate a range of fuels and chemicals.     

The impact of a brominated flame retardant on smoltification and olfactory function in Atlantic salmon (Salmo salar L.) smolts

Despite a reduction in exploitation of salmon stocks throughout the NE Atlantic, there continues to be a decline in many populations. The factors regulating these populations remain poorly understood, although there is evidence that environmental conditions experienced in freshwater can effect survival in the marine environment. The aim of this study was to investigate the impact of a brominated flame retardant (hexabromocyclododecane, HBCD) on the parr-smolt transformation in juvenile salmon. It is during this pre-adaptive period to marine life that olfactory imprinting to the natal river is considered to occur. Fish were exposed to low levels of HBCD for 30 days over the peak smoltification period in freshwater, and then transferred to clean seawater for 20 days. Fish were sampled weekly to assess changes in some of the physiological parameters associated with smoltification, and olfactory response to conspecific smolt urine was measured using an electro-olfactogram (EOG). Exposure to HBCD did not affect seawater adaptability, although there was some disruption of plasma thyroid hormone levels, as well as a reduction in olfactory function to conspecific smolt urine. The results are discussed in relation to the marine survival and successful homing of adult salmon.     

中药及其水煎液中微量元素含量研究

采用火焰原子吸收光谱法(flame atomic absorption spectrometry,FAAS)测定了黄芪、白术、防风及玉屏风散各次水煎液中铁、铜、锰、铅4种微量元素的含量。结果表明,中药各次水煎液中微量元素的浸出率各不相同,应合理用药,以更好地发挥中药的疗效。     

Mechanisms of EDDHA effects on the promotion of floral induction in the long-day plant Lemna minor (L.)

EDDHA added in an optimal concentration (20.5 mumol.L-1) to a modified Pirson-Seidel nutrient solution induces flowering in some clones of the species Lemna minor, Lemna gibba and Spirodela polyrrhiza, which in the absence of EDDHA in the same nutrient solution do not flower. By adding EDDHA (20.5 mumol.L-1), floral induction under LD conditions is optimally promoted in the long-day (LD) species Lemna minor. After adding EDDHA to the nutrient solution, before floral induction and during flowering, Zn, Mn and Cu content is significantly increased in plants. Zn-EDDHA (0.86 mumol.L-1), Mn-EDDHA (1.51 mumol.L-1) and Cu-EDDHA (0.12 mumol.L-1), when used individually, greatly promote flowering under LD conditions as compared to flowering in the same nutrient solution with an equivalent quantity of Zn, Mn or Cu in the nonchelate form. If, on the other hand, Zn-EDDHA and Mn-EDDHA are added to the nutrient solution together (instead of Zn and Mn in nonchelate form), their effect on the promotion of flowering is less than in the case of their individual use. This shows that there is antagonism between Zn-EDDHA and Mn-EDDHA that is eliminated by adding EDDHA to the nutrient solution. We obtained the highest percentage of flowering plants (i.e. 74%) if we added EDDHA (20.5 mumol.L-1) to the nutrient solution containing Mn, Zn and Cu in chelate form. 74% of flowering plants actually means that flowering was achieved in all physiologically mature plants. Our results show that EDDHA promotes floral induction in Lemna minor under LD conditions, especially through chelating Zn, Mn and Cu, and, in addition, through eliminating the antagonism between Mn and Zn chelates EDDHA. Zn-EDDHA (0.86 mumol.L-1) also promote floral differentiation, especially cell division of microspore mother cells into dyads and those into microspore tetrads, which can be seen in microphotographs. When investigating possible pathways through which Mn-EDDHA, Zn-EDDHA and Cu-EDDHA promote flowering, we studied the effects of various concentrations of IAA and sucrose added to the nutrient solution as well. The results support the hypothesis that one of the possible pathways in which Mn-EDDHA promotes floral induction is through auxin oxidase, whereas Zn-EDDHA and Cu-EDDHA probably promote it through the enhancement of the photosynthesis and synthesis of sucrose.     

Enrichment of a Microbial Culture Capable of Reductive Debromination of the Flame Retardant Tetrabromobisphenol-A, and Identification of the Intermediate Metabolites Produced in the Process

Tetrabromobisphenol-A is a reactive flame retardant used in the production of many plastic polymers. In previous research, it was demonstrated that anaerobic microorganisms from contaminated sediment debrominate tetrabromobisphenol-A to bisphenol-A, but an enrichment culture was not established. The current study was carried out to identify the intermediate metabolites in this process and to determine the factors facilitating enrichment of debrominating microorganisms. During the enrichment process in an anaerobic semi-continuous batch reactor, tetrabromobisphenol-A debromination gradually slowed down with concurrent accumulation of three intermediate products. These compounds were tentatively identified using GC-MS as tri-, di-, and mono-brominated bisphenol-A. GC-MS and HPLC analyses showed one dominant metabolite of dibromobisphenol-A, and NMR analysis identified it as 2,2'-dibromobisphenol-A. Addition of sterile sediment(15% wt/wt) to the reactor stimulated debromination of tetrabromobisphenol-A.Furthermore, different solid amendments such as surface soil and pulverized gray chalk from the site subsurface (100 m below ground) were also stimulating agents.We conclude that organic matter is involved in stimulation since the stimulationeffect of the sediment, soil and gray chalk was abolished after it was heat-treatedto 550 °C. Our study suggests that the debrominating culture requires someorganic components found in the sediment, soil, and chalk in order to sustain activityand perhaps to survive. The possible mechanisms of stimulation by these solids arediscussed.