Epoxide ring opening in a zinc(II) complex in water without any Lewis acid catalyst: Formation of only one diastereomer out of 2

The epoxide ring in 5,6-dihydro-5,6-epoxy-1,10-phenanthroline (L) opens up in its reaction with 4-methylaniline and 4-methoxyaniline in water in equimolar proportion at room temperature without any Lewis acid catalyst to give a monohydrate of 6-(4-methyl-phenylamino)-5,6-dihydro-1,10-phenanthrolin-5-ol (L′·H₂O) and 6-(4-methoxyphenyl-amino)-5,6-dihydro-1,10-phenanthrolin-5-ol (L″) respectively. Reaction time decreases from 72 to 14 h in boiling water. But the yields become less. Reaction of L with Zn(ClO₄)₂·6H₂O in methanol in 3:1 molar ratio at room temperature affords white [ZnL₃](ClO₄)₂·H₂O. The X-ray crystal structure of the acetonitrile solvate [ZnL₃](ClO₄)₂·MeCN has been determined which shows that the metal has a distorted octahedral N₆ coordination sphere. [ZnL₃](ClO₄)₂·2H₂O reacts with 4-methylaniline and 4-methoxyaniline in boiling water in 1:3 molar proportion in the absence of any Lewis acid catalyst to produce [ZnL′₃](ClO₄)₂·4H₂O and [ZnL″₃](ClO₄)₂·H₂O, respectively in 1-4 h time in somewhat low yield. In the ¹H NMR spectra of [ZnL′₃](ClO₄)₂·4H₂O and [ZnL″₃](ClO₄)₂·H₂O, only one sharp methyl signal is observed implicating that only one diastereomer out of the 2³ possibilities is formed. The same diastereomers are obtained when L′·H₂O and L″ are reacted directly with Zn(ClO₄)₂·6H₂O in tetrahydrofuran at room temperature in very good yields. Reactions of L′·H₂O and L″ with Ru(phen)₂Cl₂·2H₂O (phen = 1,10-phenanthroline) in equimolar proportion in methanol-water mixture under refluxing condition lead to the isolation of two diastereomers of [Ru(phen)₂L′](ClO₄)₂·2H₂O and [Ru(phen)₂L″](ClO₄)₂·2H₂O.     

Pygoscelid penguins in a swim canal

Summary In Antarctica, we investigated the energy consumption of Adélie (Pygoscelis adeliae), Gentoo (P. papua) and Chinstrap (P. antarctica) penguins while resting in the water (8.4 W-kg^–1) and swimming underwater at various speeds, using a 21m long canal filled with sea-water at 4°C in conjunction with respirometry. The birds swam at will and consumed 15.7, 16.1 and 10 W·kg^–1 at the speed where cost of transport was minimal (2.1, 2.3 and 2.5 m·s^–1 in Adélie, Gentoo and Chinstrap penguins, respectively). Thermal conductance in pygoscelid penguins was 3.3 W·°C^–1. m^–2 and energy expenditure (P_i, W·kg^–1) while resting in the water is given by P_j = -0.3 t_a+9.6, where t_a is water temperature in °C. During the breeding season, pygoscelid penguins spend 25–40% of their daily energy expenditure while foraging at sea. The importance of accurate estimates of at-sea activity and energy consumption is discussed.     

Role of ethylene in postharvest quality of cut oriental lily ‘Stargazer’

The effects of endogenous and exogenous C₂H₄ and C₂H₄ inhibitors on the postharvest leaf and flower quality of Oriental lily Stargazer were investigated. Endogenous C₂H₄ was not produced by freshly harvested excised leaves or flowers. Treatment of freshly harvested excised flowers, buds, leaves, and intact cut stems with C₂H₄ concentrations as high as 10 µl·l^–1 did not affect bud opening or longevity or the development of leaf yellowing. Therefore, treatment with anti-C₂H₄ compounds, such as silver thiosulfate (STS) and 1-methylcyclopropene (1-MCP), did not improve the quality of the flowers. Data thus indicate that freshly harvested Stargazer were not sensitive to C₂H₄. Sensitivity of Stargazer to C₂H₄, however, increased dramatically following cold storage, as exposure of cold-stored stems to C₂H₄ concentrations as low as 0.3 µl·l^–1 significantly affected bud opening. The development of leaf yellowing on cold-stored stems was not affected by the exogenous C₂H₄. Pretreating cold-stored stems with 1-MCP significantly reduced blasting of small buds that failed to develop due to carbohydrate depletion and reduced the percentage of buds that did not fully open. Concurrently, 1-MCP did not affect the quality of the leaves. These data indicate that sensitivity of cut lilies to C₂H₄ differs following cold storage and that 1-MCP is a more suitable anti-C₂H₄ compound than STS. Furthermore, studies on endogenous C₂H₄ production revealed that, while C₂H₄ was not detected in freshly harvested buds and leaves, it was produced by both following cold storage. The latter produced C₂H₄ at a higher rate than the former. Results of this study clearly indicate that there are two situations in which lilies will benefit from pretreatment with an anti-C₂H₄ compound (1) when cut stems contain buds that are marginally small for opening and (2) when cut stems will be cold stored before marketing.     

Expression of Peroxidases During Seedling Growth in <Emphasis Type="Italic">Ebenus Cretica</Emphasis> L. as Affected by Light and Temperature Treatments

Peroxidase (POD) activity and isoform patterns were investigated during seedling growth (up to 20 days) of Ebenus cretica L. Seeds germinated to approx. 100% after a 24-h imbibition. Seedling growth proceeded smoothly, in both light and dark conditions. No seedling growth was noticed at 4°C. A positive effect of light and increasing temperature (4, 10, 16, 22 and 28°C) on seedlings growth, lignin content and POD activity was observed. Lignin content was 2.5 times higher in seedlings grown under light than in seedlings grown under darkness. Seedlingsȁ9 POD activity was higher in acid pH (5.5) in comparison to neutral pH (7.0). These activities were higher in seedlings grown under darkness than in those grown under light; since additional POD isoforms were expressed in dark conditions. The increase in POD activity was accompanied with the appearance of new POD isoforms correlated with the growth of the seedlings. Four soluble anionic POD isoforms (named A₁, A₂, A₃ and A₄) and three soluble cationic POD isoforms (named C₁, C₂ and C₃) were displayed depending on the treatment and the course of growth. POD isoforms were detected in gel after PAGE. The fast migrating (A₄) isoform, which appeared in the dark-grown seedlings as well as on day 20 at 28°C in the temperature treatment, was separated by DEAE–Sepharose column chromatography. A slow migrating C₁ isoform slightly appeared in both 4 and 10°C temperature treatments and could be related to the low temperature treatments, while A₁, A₂, A₃ and C₂ to the growth stage of seedlings. The expression of seven POD isoforms during seedling growth seems to be related to different developmental events of growth and could be used as useful biochemical markers in the analysis of metabolic regulation in seedling growth of Ebenus cretica.     

Analysis and in situ hybridization of cryptic satellites in Hordeum arizonicum

Summary Three satellites, one (H₁) on the heavy side of the main band of Hordeum arizonicum DNA and two (L₁, L₂) on the lighter side were purified using preparative silver-cesium sulphate density gradients. The native and the reassociated satellite DNAs were analysed in terms of buoyant densities and thermal dissociation. In cesium chloride gradients the H₁ and L₁ satellites formed single peaks corresponding to buoyant densities of 1.700 and 1.701 g · cm^–3 respectively while the L₂ satellite gave two peaks (1.680 and 1.661 g · cm^–3). The H₁ satellite showed three thermal components (Tm=82.5 °C, 87 °C and 91.5 °C) while the L₁ and L₂ had three (86.5, 92, 97.5 °C) and two (86, 95 °C) respectively. The H₁ satellite was localized on the nuclei and chromosomes. The distribution of H₁ onto approximately on third of the complement may reflect the genome specific origin of this satellite.     

Nitrogenase activity in Rhodopseudomonas sulfidophila

The marine purple nonsulfur bacterium, Rhodopseudomonas sulfidophila, strain W4, was capable of photosynthetic growth on dinitrogen and malate. Higher growth rates were observed when either glutamate or ammonia replaced dinitrogen as nitrogen source and when bicarbonate was omitted from the culture medium. Although ammonia was released from cells growing on malate and N₂, no nitrogenase activity could be detected unless -ketoglutarate was added to the culture medium. No nitrogenase activity was found in cultures grown in the presence of NH ₄ ⁺ . In cultures grown on glutamate as nitrogen source, nitrogenase and hydrogenase activities were found to be 5.4 nmol C₂H₂ reduced · min^-1 · mg^-1 dry weight and 50 nmol methylene blue reduced · min^-1 · mg^-1 dry weight respectively. Such activities are significantly lower than those observed for other members of the Rhodospirillaceae e.g. Rhodopseudomonas capsulata. However, the hydrogenase activity would be sufficient to recycle all H₂ produced by nitrogenase. It was indeed observed that growing cells did not evolve molecular hydrogen during photoheterotrophic growth and that H₂ stimulated nitrogenase activity in resting cells of R. sulfidophila. The nitrogenase from this bacterium proved to be extremely sensitive to low concentrations of oxygen, half-inhibition occurring at between 1–1.5% O₂ in the gas phase, depending on the bacterial concentration. Light was essential for nitrogenase activity. No activity was found during growth in the dark under extremely low oxygen concentrations (1–2% O₂), which are still sufficient to support good growth. Resting cell suspensions prepared from such cultures were unable to reduce acetylene upon illumination. Optimum nitrogenase activities were broadly defined over the temperature range, 30–38°C, and between pH 6.9 and 8.0. The results are discussed in comparison with the non-marine purple nonsulfur bacterium, R. capsulata, which somewhat resembles R. sulfidophila.     

Cycling of inorganic and organic sulfur in peat from Big Run Bog,West Virginia

Total S concentration in the top 35 cm of Big Run Bog peat averaged 9.7 mol·g — wet mass^–1 (123 mol·g dry mass^–1). Of that total, an average of 80.8% was carbon bonded S, 10.4% was ester sulfate S, 4.5% was FeS₂­S, 2.7% was FeS­S, 1.2% was elemental S, and 0.4% was SO₄ ^2–­S. In peat collected in March 1986, injected with³⁵S­SO₄ ^2– and incubated at 4 °C, mean rates of dissimilatory sulfate reduction (formation of H₂S + S⁰ + FeS + FeS₂), carbon bonded S formation, and ester sulfate S formation averaged 3.22, 0.53, and 0.36 nmol·g wet mass^–1·h^–1, respectively. Measured rates of sulfide oxidation were comparable to rates of sulfate reduction. Although dissolved SO₄ ^2– concentrations in Big Run Bog interstitial water (< 200 µM) are low enough to theoretically limit sulfate reducing bacteria, rates of sulfate reduction integrated throughout the top 30–35 cm of peat of 9 and 34 mmol·m^–2·d^–1 (at 4 °C are greater than or comparable to rates in coastal marine sediments. We suggest that sulfate reduction was supported by a rapid turnover of the dissolved SO₄ ^2– pool (average turnover time of 1.1 days). Although over 90% of the total S in Big Run Bog peat was organic S, cycling of S was dominated by fluxes through the inorganic S pools.     

Syntheses, crystal structures and magnetic properties of trinuclear and [3 × 1 + 1 × 2] pentanuclear complexes derived from a compartmental ligand: Role of solvent on nuclearity and number of components

Reaction of [Cu^IIL⊂(H₂O)] (H₂L = N,N′-ethylenebis(3-ethoxysalicylaldimine)) with nickel(II) perchlorate in 1:1 ratio in acetone produces the trinuclear compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂ (1). On the other hand, on changing the solvent from acetone to methanol, reaction of the same reactants in same ratio produces the pentametallic compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)]·2MeOH (2A), which loses solvated methanol molecules immediately after its isolation to form [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)] (2B). Clearly, formation of 1 versus 2A and 2B is solvent dependent. Crystal structures of 1 and 2A have been determined. Interestingly, compound 2A is a [3 × 1 + 1 × 2] cocrystal. The cryomagnetic profiles of 1 and 2B indicate that the two pairs of copper(II)···nickel(II) ions in the trinuclear cores in both the complexes are coupled by almost identical moderate antiferromagnetic interaction (J = −22.8 cm⁻¹ for 1 and −26.0 cm⁻¹ for 2B).     

The roles of malate and aspartate in C4 photosynthetic metabolism of Flaveria bidentis (L.)

In C₄ grasses belonging to the NADP-malic enzyme-type subgroup, malate is considered to be the predominant C₄ acid metabolized during C₄ photosynthesis, and the bundle sheath cell chloroplasts contain very little photosystem-II (PSII) activity. The present studies showed that Flaveria bidentis (L.), an NADP-malic enzyme-type C₄ dicotyledon, had substantial PSII activity in bundle sheath cells and that malate and aspartate apparently contributed about equally to the transfer of CO₂ to bundle sheath cells. Preparations of bundle sheath cells and chloroplasts isolated from these cells evolved O₂ at rates between 1.5 and 2 mol · min^–1 · mg^–1 chlorophyll (Chl) in the light in response to adding either 3-phosphoglycerate plus HCO ₃ ^– or aspartate plus 2-oxoglutarate. Rates of more than 2 mol O₂ · min^–1 · mg^–1 Chl were recorded for cells provided with both sets of these substrates. With bundle sheath cell preparations the maximum rates of light-dependent CO₂ fixation and malate decarboxylation to pyruvate recorded were about 1.7 mol · min^–1 · mg^–1 Chl. Compared with NADP-malic enzyme-type grass species, F. bidentis bundle sheath cells contained much higher activities of NADP-malate dehydrogenase and of aspartate and alanine aminotransferases. Time-course and pulse-chase studies following the kinetics of radiolabelling of the C-4 carboxyl of C₄ acids from ¹⁴CO₂ indicated that the photosynthetically active pool of malate was about twice the size of the aspartate pool. However, there was strong evidence for a rapid flux of carbon through both these pools. Possible routes of aspartate metabolism and the relationship between this metabolism and PSII activity in bundle sheath cells are considered.Abbreviations DHAP dihydroxyacetone phosphate - NADP-ME(-type) NADP-malic enzyme (type) - NADP-MDH NADP-malate dehydrogenase - OAA oxaloacetic acid - 2-OG 2-oxoglutarate - PEP phosphoenolpyruvate - PGA 3-phosphoglycerate - Pi orthophosphate - Ru5P ribulose 5-phosphate     

Inhibition of photosynthesis by chilling in moderate light: a comparison of plants sensitive and insensitive to chilling

Photosynthetic activity, in leaf slices and isolated thylakoids, was examined at 25° C after preincubation of the slices at either 25° C or 4° C at a moderate photon flux density (PFD) of 450 mol·m^–2·s^–1, or at 4° C in the dark. The plants used wereSpinacia oleracea L.,Cucumis sativus L. andNerium oleander L. which was acclimated to growth at 20° C or 45° C. The plants were grown at a PFD of 550 mol·m^–2·s^–1. Photosynthesis, measured as CO₂-dependent O₂ evolution, was not inhibited in leaf slices from any plant after preincubation at 25° C at a moderate PFD or at 4° C in the dark. However, exposure to 4° C at a moderate PFD induced an inhibition of CO₂-dependent O₂ evolution within 1 h inC. sativus, a chilling-sensitive plant, and in 45° C-grownN. oleander. The inhibition in these plants after 5 h reached 80% and 40%, respectively, and was independent of the CO₂ concentration but was reduced at O₂ concentrations of less than 3%. Methyl-viologen-dependent O₂ exchange in leaf slices from these plants was not inhibited. There was no photoxidation of chlorophyll, in isolated thylakoids, or any inhibition of electron transport at photosystem (PS)II, PSI or through both photosystems which would account for the inhibition of photosynthesis. The conditions which inhibit photosynthesis in chilling-sensitive plants do not cause inhibition inS. oleracea, a chilling-insensitive plant, or in 20° C-grownN. oleander. The CO₂-dependent photosynthesis, measured at 5° C, was reduced to about 3% of that recorded at 25° C in chilling-sensitive plants but only to about 30% in the chilling-insensitive plants. Methyl-viologen-dependent O₂ exchange, measured at 5° C, was greater than 25% of the activity at 25° C in all the plants. The results indicate that the mechanism of the chilling-induced inhibition of photosynthesis does not involve damage to PSII. That inhibition of photosynthesis is observed only in the chilling-sensitive plants indicates it is related, in some way, to the disproportionate decrease in photosynthetic activity in these plants at chilling temperatures.Abbreviations Chl chlorophyll - DPIPH reduced form of 2,6-dichlorophenol-indophenol - DMQ 2,5-dimethyl-p-benzoquinone - MV methyl viologen - 20°-oleander Nerium oleander grown at 20° C - 45°-oleander N. oleander grown at 45° C - PFD photon flux density (photon fluence rate) - PSI and PSII photosystem I and II, respectively     

Beta-adrenergic control of trans-cutaneous evaporative cooling mechanisms in birds

Summary The decreasing effect of -adrenergic blockade on skin resistance to vapor diffusion and the onset of cutaneous water evaporation in the pigeon (Columba livia) was investigated. Oral administration of 1, 2.3 and 5 mg propranolol to pigeons (268±53 g) initiated intensive trans-cutaneous water evaporation (CWE) up to 29.1 mg H₂O·cm^–2·h^–1 in resting birds at 30°C air temperature (Ta), but had only a slight effect on CWE of birds exposed to 50 °C Ta.After 7 h of effective -adrenergic blockade (oral administration of 5 mg propranolol), skin and body temperature stabilized at 39.0±0.5 °C and 41.0±0.7 °C, compared to 40.2±0.8 °C and 41.9±0.6 °C in the control group, respectively. A slight hypothermia was accompanied by feather fluffing.Intradermal injection of 0.001, 0.01 and 0.12 mg propranolol also caused intensive CWE. Local -adrenergic blockade in relatively low blocker doses (0.001 and 0.01 mg propranolol) decreased skin resistance from a high value of 44.5 s·cm^–1 to about 6.0 s·cm^–1, and caused a sharp increase in CWE from a control value of about 4 to a high of 26.4 mg H₂O·cm^–2·h^–1 during the first two hours of exposure to 30°C Ta.The possible role of -adrenergic blockade in regulation of trans-cutaneous water evaporation of latent heat dissipation is discussed.     

Temperature insensitive O2 in blood of the tree frogChiromantis petersi

Summary Respiratory gas exchange and blood respiratory properties have been studied in the East-African tree frogChiromantis petersi. This frog is unusually xerophilous, occupies dry habitats and prefers body temperatures near 40°C and direct solar exposure. Total O₂ uptake was low at 81 l O₂·g^–1·h^–1±19.0 (SD) at 25°C increasing to 253.5 l O₂·g^–1·h^–1±94.8 (SD) at 40°C giving aQ ₁₀ value of 2.1. Skin O₂ uptake at 25°C was 38.5% of total. The gas exchange ratio was 0.71 for whole body gas exchange, 0.61 for the lungs and 1.02 for the skin at 25°C.Blood O₂ affinity was low with aP ₅₀ of 47.5 mmHg at 25°C and pH 7.65. Then _H-value at 25°C increased from 2.7 aroundP ₅₀ to 5.0 at O₂ saturations exceeding 70–80%. Surprisingly, blood O₂ affinity was nearly insensitive to temperature expressed by a H value of ±1.0 kcal·mole between 25 and 40°C.The adaptive significance of the low O₂ affinity, the increase ofn _H with O₂ saturation and the temperature insensitive O₂-Hb binding is discussed in relation to the high and fluctuating body temperatures ofChiromantis.     

Photobiont-related differences in carbon acquisition among green-algal lichens

The photosynthetic properties of a range of lichens (eight species) containing green algal primary photobionts of either the genus Coccomyxa, Dictyochloropsis or Trebouxia were examined with the aim of obtaining a better understanding for the different CO₂ acquisition strategies of lichenized green algae. Fast transients of light/dark-dependent CO₂ uptake and release were measured in order to screen for the presence or absence of a photosynthetic CO₂-concentrating mechanism (CCM) within the photobiont. It was found that lichens with Trebouxia photobionts (four species) were able to accumulate a small pool of inorganic carbon (DIC; 70–140 nmol per mg chlorophyll (Chl)), in the light, which theoretically may result in, at least, a two to threefold increase in the stromal CO₂ concentration, as compared to that in equilibrium with ambient air. The other lichens (four species), which were tripartite associations between a fungus, a cyanobacterium (Nostoc) and a green alga (Coccomyxa or Dictyochloropsis) accumulated a much smaller pool of DIC (10–30 nmol·(mg Chl)^–1). This pool is most probably associated with the previously documented CCM of Nostoc, inferred from the finding that free-living cells of Coccomyxa did not show any signs of DIC accumulation. In addition, the kinetics of fast CO₂ exchange for free-living Nostoc were similar to those of intact tripartite lichens, especially in their responses to the CCM and the carbonic anhydrase (CA) inhibitor ethoxyzolamide. Trebouxia lichens had a higher photosynthetic capacity at low and limiting external CO₂ concentrations, with an initial slope of the CO₂-response curve of 2.6–3.9 mol·(mg Chl)^–1·h^–1·Pa^–1, compared to the tripartite lichens which had an initial slope of 0.5–1.1 mol-(mg Chl)^–1·h^–1·-Pa^–1, suggesting that the presence of a CCM in the photobiont affects the photosynthetic performance of the whole lichen. Regardless of these indications for the presence or absence of a CCM, ethoxyzolamide inhibited the steady-state rate of photosynthesis at low CO₂ in all lichens, indicating a role of CA in the photosynthetic process within all of the photobionts. Measurements of CA activity in photobiont-enriched homogenates of the lichens showed that Coccomyxa had by far the highest activity, while the other photobionts displayed only traces or no activity at all. As the CCM is apparently absent in Coccomyxa, it is speculated that this alga compensates for this absence with high internal CA activity, which may function to reduce the CO₂-diffusion resistance through the cell.Abbreviations CA carbonic anhydrase (EC 4.2.1.1) - CCM CO₂-concentrating mechanism - Chl chlorophyll - DIC dissolved inorganic carbon - EZ ethoxyzolamide or 6-ethoxy-2-benzo-thiazole-2-sulfonamide - GA glycolaldehyde - Hepps 4-(2-hydroxyethyl)-l-piperazinepropanesulfonic acid - Rubisco ribulose-1,5-bisphosphate carboxylase-oxygenase (EC 4.1.1.39) This research was supported by a grant from the Swedish Natural Sciences Resource Council to K.P.     

Protonated N-heterocycle-templated supramolecular frameworks built of triangular molybdenum(IV) clusters

A series of porous supramolecular complexes (Hoxine)₂ · [Mo₃O₄(C₂O₄)₃(H₂O)₃] · 5H₂O (1),(Hphen)₂ · [Mo₃O₄(C₂O₄)₃(H₂)₃]  · 0.5C₂H₅OH · 7H₂O (2), H₂bpy · [Mo₃O₄(C₂O₄)₃(H₂O)₃] · 2.5H₂O (3), H₂TTD · [Mo₃O₄(C₂O₄)₃(H₂O)₃] · C₂H₅OH · 3H₂O (4), (oxine = 8-hydroxyquinoline, phen = 1,10-phenanthroline, bpy = 4,4′-bipyridine, TTD = triethylene diamine) have been prepared and characterized by single-crystal X-ray crystallography, elemental analysis and infrared spectroscopy. Self-assembly of [Mo₃O₄(C₂O₄)₃(H₂O)₃]²⁻ directed by H-bonding association between the coordination water molecules and oxalate groups forms 2-D host H-bonded single layer in 1, double layer in 2 and 3, and undulated layer in 4 depending on the nature of the guest protonated N-heterocycles. Unlike cis-Hoxine⁺ or Hphen⁺ that employs lattice water molecules H-bonded to them to interconnect the host layers, trans-H₂bpy²⁺ or H₂TTD²⁺ acts a linker between the neighboring host layers to form 3-D supramolecular frameworks with channeled structures wherein the guest protonated cations are located.     

Nitrogen fixation by Nodularia spumigena Mertens (Cyanobacteriaceae). 1: Field studies and the contribution of blooms to the nitrogen budget of the Peel-Harvey Estuary,Western Australia

Variations in nitrogen fixation (acetylene reduction) by Nodularia spumigena blooms in the Peel-Harvey estuarine system were examined with respect to spatial (sampling station location, and depth) and temporal (seasonal and diurnal) distribution. The annual contributions of nitrogen fixation by the blooms to the nitrogen budget of the estuary were estimated to range from 309 to 713t. Contributions by nitrogen fixation were similar to the riverine inputs in the Harvey Estuary, but lower in the Peel Inlet.The Harvey Estuary had higher biomass and total fixation rates (to 0.4 nmol C₂H₂ · ml^–1 h^–1), but the heterocyst nitrogen fixation rates were greater in the Peel Inlet (to 9 × 10^–1 nmol C₂H₂ · heterocyst^–1 · h^–1). Nitrogen fixation decreased with depth in response to light, though other factors also appeared to be involved. The rates of fixation decreased concurrently with increasing bloom age, total soluble inorganic nitrogen and salinities. Maximum daily fixation rates occurred in the early morning.     

Amelioration of chilling stress by triadimefon in cucumber seedlings

Cucumber (Cucumis satvus L.) seeds were imbibed in distilled water (control) and 10 mg l^–1 triadimefon (TDM) for 10 h and then grown in a plant growth chamber with a light/dark temperature of 28/20 °C and a photoperiod of 14 h with a light intensity of 60 µmol m^–2 s^–1. 14-day-old seedlings were exposed to chilling stress with a light/dark temperature of 6/3 °C for 4 d. TDM improved the growth rate of cucumber seedling subjected to chilling stress and increased photosynthetic pigments contents and relative water content compared with the control at the end of chilling stress. Chilling stress decreased protein content and the activities of SOD, CAT and POD, but it increased proline, H₂O₂ and MDA accumulation, and relative electrical conductivity. TDM ameliorated the injury caused by chilling stress by preventing decreases in protein content and the activities of SOD, CAT and POD and by inhibiting increases in proline, H₂O₂ and MDA contents, and relative electrical conductivity, which suggested that TDM ameliorated the negative effect of chilling stress.     

Sequence of Chloroplast Degreening in Calamondin Fruit as Influenced by Ethylene and AgNO(3)

C₂H₄ disrupts the internal membranes of the chloroplast and induces an increase in chlorophyllase activity in degreening calamondin [x Citrofortunella mitis (Blanco) Ingram and Moore] fruit. Whether the loss of chlorophyll in the peel is causally related to breakdown of the chloroplast and/or chlorophyllase activity is not readily apparent. Chlorophyllase levels were inversely related to chlorophyll content, but electron micrographs also showed that internal membranes of the chloroplasts were disrupted simultaneously with the decrease in chlorophyll content. Silver, a potent inhibitor of C₂H₄-mediated effects, retarded the loss of chlorophyll in calamondin rind, reduced the C₂H₄-induced increase in chlorophyllase level, and prevented the disruption of the chloroplast membranes. The results do not permit the proposal of a mechanism of C₂H₄ metabolism in the degreening of calamondin fruit.     

The compartmentation of ethylene in developing cotyledons of Phaseolus vulgaris L.

Isolated cotyledons of Phaseolus vulgaris L. cv. Canadian Wonder accumulated ¹⁴C₂H₄ (0.7–1 l l^-1) from air to give partition coefficients of 1 to 4, which greatly exceeded the value obtained with steam killed cotyledons (0.05) and with water (0.11). After ¹⁴C₂H₄ treatment, 98% of the ¹⁴C in the tissue remained as ¹⁴C₂H₄. The labelled ethylene accumulated by cotyledons was released only slowly (1–10% h^-1) either in an air stream or into toluene. Heating to 60°C for 2 h, but not freezing and thawing, caused the immediate release of ¹⁴C₂H₄ from the tissue. Propylene and vinyl chloride competitively inhibited the accumulation of ¹⁴C₂H₄.Cotyledons emanated endogenous ethylene at a very low rate but after heating (although not freezing and thawing) 13 nl of ethylene per g fresh mass were released within minutes. It was concluded that french bean cotyledons hold ethylene in a compartmented form in sufficient amount to account for at least 200 h of emanation.Abbreviation PPO diphenyloxazole     

Synthesis, crystal structures and luminescent properties of manganese and zinc complexes with in situ ligand formation of 3-amino-4-(5-tetrazolyl)-1H-pyrazole

Three metal-organic frameworks, [Mn(HL)(N₃)] (1), [Mn(HL)Cl(H₂O)] (2) and [Zn₂(L)₂(H₂O)] (3) where H₂L = 3-amino-4-(5-tetrazolyl)-1H-pyrazole, have been yielded through in situ hydrothermal reactions of manganese(II) or zinc(II) salts, NaN₃ and 3-amino-4-cyano-1H-pyrazole (HACP). The crystal structure analysis reveals that 1-3 have different dense 3D frameworks with Schläfli symbols of {3·4²·5²·6}{3²·4³·5⁴·6⁶} for 1 which is an unprecedented (4,6)-connected framework, {4·12²}2{4²·12⁴} for 2 which is a typical sqc519 structure, and {4²·6}2{4⁴·6²·8⁸·10} for 3 which is a typical ant/anatase structure, respectively. The ligand takes three different coordination modes in 1-3 as 3- or 4-connector. In addition, the photoluminescence of complex 3 was studied in solid state at room temperature, together with its thermal analysis.     

Photosynthetic production of hydrogen peroxide by Ulva rigida C. Ag. (Chlorophyta)

Production of hydrogen peroxide has been found in Ulva rigida (Chlorophyta). The formation of H₂O₂ was light dependent with a production of 1.2 mol·g FW^–1·h^–1 in sea water (pH 8.2) at an irradiance of 700 mol photons m^–2·s^–1. The excretion was also pH dependent: in pH 6.5 the production was not detectable (< 5 nmol·g FW^–1·h^–1) but at pH 9.0 the production was 5.0 mol·g FW^–1·h^–1. The production of H₂O₂ was totally inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU). The ability of U. rigida growing in tanks (7501) under a natural light regime to excrete H₂O₂ was checked and found to be seven times higher at 08.00 hours than other times of the day. The H₂O₂ concentration in the cultivation tank (density: 2 g FW·l^–1) reached the highest value (3 M) at 11.00 hours. Photosynthesis was not influenced by H₂O₂ formation. The H₂O₂ is suggested to come from the Mehler reaction (pseudocyclic photophosphorylation). With an oxygen evolution of 120 mmol·g FW^–1·h^–1 at pH 8.2 and 90 mmol·g FW^–1·h^–1 at pH 9.0, 0.5% and 2.7% of the electrons were used for extracellular H₂O₂ production. The H₂O₂ production is sufficiently high to be of physiological and ecological significance, and is suggested to be a part of the defence against epi and endophytes.Abbreviations ACL artificial, continuous light - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - GNL greenhouse - LDC Luminol-dependent chemiluminescence - SOD Superoxide dismutase This investigation was supported by SAREC (Swedish Agency for Research Cooperation with Developing Countries), Hierta-Retzius Foundation, Marianne and Marcus Wallenberg Foundation, the Swedish Environmental Protection Board, and CICYT Spain.