Kinetics and thermodynamics of peroxidase- and laccase-catalyzed oxidation of N-substituted phenothiazines and phenoxazines

N -substituted phenothiazines (PTs) and phenoxazines (POs) catalyzed by fungal Coprinus cinereus peroxidase and Polyporus pinsitus laccase were investigated at pH 4–10. In the case of peroxidase, an apparent bimolecular rate constant (expressed as k _cat/K _m) varied from 1 ×10⁷M⁻¹s⁻¹to 2.6×10⁸M⁻¹s⁻¹ at pH 7.0. The constants for PO oxidation were higher in comparison to PT. pH dependence revealed two or three ionizable groups with pK _a values of 4.9–5.7 and 7.7–9.7 that significantly affected the activity of peroxidase. Single-turnover experiments showed that the limiting step of PT oxidation was reduction of compound II and second-order rate constants were obtained which were consistent with the constants at steady-state conditions. Laccase-catalyzed PT and PO oxidation rates were lower; apparent bimolecular rate constants varied from 1.8×10⁵M⁻¹s⁻¹ to 2.0×10⁷M⁻¹s⁻¹ at pH 5.3. PO constants were higher in comparison to PT, as was the case with peroxidase. The dependence of the apparent bimolecular constants of compound II or copper type 1 reduction, in the case of peroxidase or laccase, respectively, was analyzed in the framework of the Marcus outer-sphere electron-transfer theory. Peroxidase-catalyzed reactions with PT, as well as PO, fitted the same hyperbolic dependence with a maximal oxidation rate of 1.6×10⁸M⁻¹s⁻¹ and a reorganization energy of 0.30 eV. The respective parameters for laccase were 5.0×10⁷M⁻¹s⁻¹ and 0.29 eV. Received: 20 September 1999 / Accepted: 24 February 2000     

Influences of the number of fetuses and levels of CP and ME in gestation and lactation supplements on performance of Spanish does and kids during suckling and post-weaning

Forty-eight mature US Spanish does (40 kg BW), from a herd selected for cashmere fiber growth, were used to investigate influences of the number of fetuses and levels of ME and CP in supplements during gestation and lactation on doe and kid performance. At 60 days of gestation, does with single or twin fetuses consumed mature Bermudagrass hay ad libitum and 1% BW (DM basis) of supplements with 18.6% or 28.5% CP (LP and HP, respectively) and 2.2 or 2.8 Mcal/kg ME (DM basis; LE and HE, respectively). The HE-HP supplement was offered at 1.5% BW (DM basis) for 15 days after birth, and does received the same supplement treatments as in gestation thereafter until weaning at 50 days after parturition. For a 50-day post-weaning period, kids consumed ad libitum the HE-LP supplement. BW at 90 days of gestation (41.4 vs 38.4 kg; P<0.10), BW before parturition (46.1 vs 41.7 kg; P<0.05), BW loss from parturition to day 21 of lactation (8.38 vs 5.25 kg; P<0.05), litter birth weight (5.47 vs 2.75 kg; P<0.05) and plasma concentrations of β-hydroxybutyrate (0.33 vs 0.29 mM; P<0.05) and NEFA (538 vs 434 mEq/l; P<0.05) were greater for does with twin vs single kids. BW at weaning was similar between single and twin kids (P>0.10; 8.31 and 7.63, respectively). Kid BW and cashmere fiber weight after the post-weaning period were affected by interactions (P<0.05) between number of fetuses and supplement ME level; kid BW was 12.3, 14.7, 14.6 and 13.2 kg (SE = 1.12 and 0.68 kg for singles and twins, respectively), and kid cashmere weight was 86, 109, 106 and 102 g (SE = 8.5 and 5.0 g for singles and twins, respectively) for single-HE, single-LE, twin-HE and twin-LE, respectively. In conclusion, effects of supplements differing in levels of ME and in ingredient composition for US Spanish does in gestation and lactation had dissimilar impacts on post-weaning BW and cashmere weight of single and twin kids. However, because of the limited number of observations and the high variability among animals in measures such as cashmere fibre growth, further experimentation concerning the potential for effects of nutritional plane of does on cashmere growth by kids is warranted.     

Comparative studies of effect of auxin and ethylene on permeability and synthesis of RNA and protein

The effects of ethylene on permeability and RNA and protein synthesis were assayed over a 6 to 26 hr period in tissue sections from avocado (Persea gratissima Gaertn. F., var. Fuerte), both pulp and peel of banana (Musa sapientum L., var. Gros Michel), bean endocarp (Phaseolus vulgaris L., var. Kentucky Wonder Pole beans) and leaves of Rhoeo discolor. Ethylene had no effect on permeability in 4 of the 5 tissues, but sometimes enhanced solute uptake in banana peel; it had either no effect or an inhibitory effect on synthesis of RNA and protein in sections from fruits of avocado and banana. Auxin (α-naphthalene acetic acid) stimulated synthesis of RNA and protein in bean endocarp and Rhoeo leaf sections, whereas ethylene inhibited both basal and auxin-induced synthesis. It is concluded that in these tissues the auxin effect is not an ethylene effect.     

Effect of soil salinity and water stresses on growth and content of nitrogen,chloride and phosphate of wheat and triticale

Summary Three wheats and one triticale were grown, up to flowering stage, in pots on calcareous soil adjusted to a range of salinities (S₁=3.5, S₂=6, S₃=8.5, and S₄=11 mmhos/cm, 20°C, soilpaste extract) by adding solution consisting of 3∶2∶1 of Na-, Ca- and Mg chlorides in chemical equivalent amounts. Moisture in the pots was kept at 100% (W₁), 40% (W₂) and 20% (W₃) of the available water. The vegetative growth, nitrogen and phosphate were affected by S and W treatments, chloride was affected only by S. The interaction S×W affected only dry weight. Varietal effect was observed between wheat as a group and triticale. Multiple quadratic regression equations of these properties on salinity and water revealed that the higher the available water the wider the range of tolerable salinity. Triticale was relatively more tolerant to water stress. Salinity increases Cl and decreases N, whereas water stress enhances N accumulation to a certain extent. However, in triticale at S₃ and S₄ the effect of water stress on N was overshadowed by the excessive salinity. This did not occur for the wheat (Florence). P trends were described. R² for P was low (0.7435–0.3603) which made interpretations rather difficult.     

Analysis of Growth and Yield of Winter and Spring Wheats

In a field experiment to investigate the physiological causesof variation in yield between autumn- and spring-sown wheatand between old and new varieties, the grain yields of the winterwheats were 3-15 per cent, greater than of the spring ones andthe new varieties Cappelle-Desprez and Jufy I yielded 40-70per cent, more than Squarehead's Master and Atle. Nitrogen fertilizerincreased the yields of Cappelle-Desprez and Jufy I more thanof Atle, and decreased the yield of Squarehead's Master by makingit lodge. Until ear emergence the winter varieties had greater leaf-areaindices (L) and dry weights, but smaller net assimilation rates(E), than the spring varieties. Square-head's Master had greaterL but smaller E, and similar dry weight to Cappelle-Desprez.Jufy I had similar E to Atlc, but greater L and dry weight.Nitrogen increased L and dry weight, but decreased E. All thedifferences in E between varieties and nitrogen treatments couldbe explained by the opposite effects on L, that is to say, thedifferences in E were caused by variation in mutual shadingarising from the differences in L and not by changes in leafphysiology. L of winter wheat reached its maximum at the end of May, butL of spring wheat continued to increase until ear emergence.Afterwards Ldecreased more rapidly for winter than for springwheat, so that eventually spring wheat had the greater L. Thesedifferences in the time changes of L partially compensated forthe shorter growth period of spring wheat, and tended to equalizethe grain yield from winter and spring sowings. After ear emergence total dry weight of winter varieties continuedto be greater than of spring ones, but the difference in dryweight of ears was much smaller because ear: shoot dry-weightratio was greater for the spring varieties. Total dry weight,ear dry weight and ear: shoot ratio were all greater in thenew than in the old varieties. Leaf area duration (D) afterear emergence was slightly greater for the winter than for thespring varieties and similar for old and new. The apparent efficiencyof this leaf area in grain production, measured by the grainleaf ratio (ratio of grain dry weight to D), was similar forwinter and spring varieties but greater for new than for old.This suggests that Cappelle-Desprez and Jufy I have higher grainyields because their ears photosynthesize more than do the earsof Squarehead's Master and Atle. Before ear emergence winter varieties had more shoots than springones, and old varieties more than new. After ear emergence therewere only small differences in numbers of ears; percentage survivalwas greater for spring than for winter and for new than forold varieties. Differences in dry weight between varieties were not causedby differences in nitrogen uptake.     

Effects of irradiance and water flow on formation and growth of spongy and filamentous thalli of Codium fragile

Effects of irradiance and water flow on formation and growth of filamentous and spongy thalli of Codium fragile (Suringar) Hariot growing on vinylon threads were investigated at the laboratory culture. They showed clear differences in their irradiance and water flow requirements for their formation and growth. Spongy thalli were formed from the cultured filamentous thalli only at the high water flow velocity (10 cm s⁻¹). Number of the spongy thalli remarkably increased with increasing irradiance because those at 10, 50 and 100 μmol m⁻² s⁻¹ reached 0, 2 and 76 thalli m⁻¹, respectively, by 10 weeks of culture. In contrast, filamentous thalli were formed from the cultured spongy thalli at 0 and 3 cm s⁻¹, and difference in irradiance had no effect on their formation. Growth of the spongy thalli greatly accelerated under the combination of the high irradiance and high water velocity (200 μmol m⁻² s⁻¹ and 10 cm s⁻¹) because their relative growth rate in wet weight under the condition was two–four times higher than those at the other examined irradiances and water velocities. On the other hand, difference in water velocity had no effect on growth of the filamentous thalli under flowing water, and their growth decelerated at the high irradiance (200 μmol m⁻² s⁻¹). This demonstrates that water flow is a major factor controlling the formation of the spongy and filamentous thalli. The formation and growth of the spongy thalli surely occur under the combination of the high irradiance and fast flowing water. In contrast, the formation of the filamentous thalli occurs in the calm water, and their growth is inhibited under the high irradiance.     

Synthesis and applications of cyclopeptides and depsipeptides

Summary A solid phase protocol has been devised for the synthesis of linear precursors to cyclic depsipeptide analogues of dolastatin D.t-Butyldimethylsilyl groups were used for hydroxy group protection, with deprotection being carried out byt-butyl ammonium fluoride. HATU and PyBrop were successful in coupling highly hindered residues and in depside bond formation. Cyclic peptide analogues, cyclo[Arg-Gly-Asp-d-Phe-Lys(or Tyr)] have been synthesised and modified for use as carrier molecules for the transport of radio isotopes (¹¹¹In and¹²⁵I) into blood platelets as prototypes for medical imaging.     

Polymorphisms of the DNA repair gene MGMT and risk and progression of head and neck cancer

Methylating agents are involved in carcinogenesis, and the DNA repair protein O⁶-methylguanine-DNA methyltransferase (MGMT) removes methyl group from O⁶-methylguanine. Genetic variation in DNA repair genes has been shown to contribute to susceptibility to squamous cell carcinoma of the head and neck (SCCHN). We hypothesize that MGMT polymorphisms are associated with risk of SCCHN. In a hospital-based case–control study of 721 patients with SCCHN and 1234 cancer-free controls frequency-matched by age, sex and ethnicity, we genotyped four MGMT polymorphisms, two in exon 3, 16195C > T and 16286C > T and two in the promoter region, 45996G > T and 46346C > A. We found that none of these polymorphisms alone had a significant effect on risk of SCCHN. However, when these four polymorphisms were evaluated together by the number of putative risk genotypes (i.e. 16195CC, 16286CC, 45996GT + TT, and 46346CA + AA), a statistically significantly increased risk of SCCHN was associated with the combined genotypes with three to four risk genotypes, compared with those with zero to two risk genotypes (adjusted odds ratio (OR) = 1.27; 95% confidence interval (CI) = 1.05–1.53). This increased risk was also more pronounced among young subjects (OR = 1.81; 95% CI = 1.11–2.96), men (OR = 1.24; 95% CI = 1.00–1.55), ever smokers (OR = 1.25; 95% = 1.01–1.56), ever drinkers (OR = 1.29; 95% CI = 1.04–1.60), patients with oropharyngeal cancer (OR = 1.45; 95% CI = 1.12–1.87), and oropharyngeal cancer with regional lymph node metastasis (OR = 1.52; 95% CI = 1.16–1.89). In conclusion, our results suggest that any one of MGMT variants may not have a substantial effect on SCCHN risk, but a joint effect of several MGMT variants may contribute to risk and progression of SCCHN, particularly for oropharyngeal cancer, in non-Hispanic whites.     

Analysis of growth and yield of inbred and crossbred maize

In experiments with young widely spaced plants grown in sand culture, net assimilation rate (E) of two single-cross hybrids, N x S and W x M, was respectively > 20% and 13–19% greater than that of their parental inbreds, N and S, and W and M. Relative growth rate (R) of W x M exceeded that of W or M, and R of N x S exceeded that of S, but not that of N because leaf area ratio (F) of this inbred was greater than that of N x S. E of N x S was about 10% greater than that of an open-pollinated variety, OP. When the size of plants of N x S was varied by sowing seeds of different sizes, E was little affected but R increased as plant size decreased, because F increased with decrease in plant size. In a field experiment total dry weights at final harvest of N, S and OP were respectively 66, 46 and 98% of that of N x S; their respective grain weights were 47, 20 and 70% of that of N x S. N, S and OP flowered later than N x S and accumulated respectively 56, 26 and 89% as much dry matter after flowering as N x S. Grain formed 71, 65, 83 and 65% of the dry matter accumulated after flowering in N, S, N x S and OP, respectively. Up to about the time of flowering, E and R of the relatively small N and S plants were greater than those of N x S plants, but later E of N and S was smaller than that of N x S. Before flowering, when leaf area of OP was less than that of N x S, E was greater in OP than in N x S. After flowering leaf area was greater, and E smaller, in OP than in N x S.     

Uptake and metabolism of glutamate and aspartate by astroglial and neuronal preparations of rat cerebellum

Astrocytes, neuronal perikarya and synaptosomes were prepared from rat cerebellum. Kinetics of high and low affinity uptake systems of glutamate and aspartate, nominal rates of¹⁴CO₂ production from [U–¹⁴C]glutamate, [U–¹⁴C]aspartate and [1–¹⁴C]glutamate and activities of enzymes of glutamate metabolism were studied in these preparations. The rate of uptake and the nomial rate of production of¹⁴CO₂ from these amino acids was higher in the astroglia than neuronal perikarya and synaptosomes. Activities of glutamine synthetase and glutamate dehydrogenase were higher in astrocytes than in neuronal perikarya and synaptosomes. Activities of glutaminase and glutamic acid decarboxylase were observed to be highest in neuronal perikarya and synaptosomes respectively. These results are in agreement with the postulates of theory of metabolic compartmentation of glutamate while others (presence of glutaminase in astrocytes and glutamine synthetase in synaptosomes) are not. Results of this study also indicated that (i) at high extracellular concentrations, glutamate/aspartate uptake may be predominantly into astrocytes while at low extracellular concentrations, it would be into neurons (ii) production of -ketoglutarate from glutamate is chiefly by way of transamination but not by oxidative deamination in these three preparations and (iii) there are topographical differences glutamate metabolism within the neurons.     

Comparison of Glycolipids and Plastids in Callus Cells and Leaves of Alnus and Betula

The fine structure of plastids and fatty acid composition ofglycolipids (e.g. monogalactosyl diacylglycerides, MGDG; digalactosyldiacylglycerides, DGDG) in callus cells of Alnus glutinosa,A. incana and Betula pendula cultured in light was comparedwith that in intact leaves. The tissues were qualitatively verysimilar but a rather high amount oflignoceric acid (24:0) wascharacteristic for the callus of A. incana. This fatty acidwas found only in trace amount in other tissues. Linolenic (18:3)and palmitic (16:0) acids are the most abundant (25–65%and 17–27% respectively) fatty acids in all tissues studied.The proportion of 18:1 and 18:2 was much higher in the calluscompared with corresponding intact leaves, which are especiallyrich (48–65%) in 18:3. In callus cultures a higher proportion(17–19%) of linoleic acid (18:2) is found in both Alnusspecies than in the two callus strains of Betula (9–12%). All leaf and callus samples contained esterified steryl glycosidesand two cerebrosidelike spots in thin-layer chromatography,but they were more prominent in callus cultures than in leaves.The callus cells have plastids with rather well developed thylakoidswhich explains the similarity of the main glycolipid components(MGDG and DGDG) to that of leaves. (Received April 23, 1984; Accepted August 17, 1984)     

Synthesis and structure of cadmium and zinc complexes of dehydroacetic acid

The cadmium and zinc complexes of Dehydroacetic Acid (DHA) Zn(DHA)₂(H₂O)₂ and Cd(DHA)₂(H₂O)₂ were synthesized and the derivatives Zn(ADH)₂(DMSO)₂ and Cd(ADH)₂(DMSO)₂ were prepared through substitution of the water ligands by DMSO. To characterize structural differences between the Cd and Zn complexes, a series of analyses were carried out: ¹H, ¹³C, and ¹¹³Cd NMR in solution and ¹³C and ¹¹³Cd NMR in the solid state, infra-red spectra, thermo gravimetric analysis (TGA), differential calorimetric analysis (DSC) and elemental analysis (CHNO). The X-ray crystal structures of the complexes Zn(DHA)₂(DMSO)₂ and Cd(DHA)₂(DMSO)₂ are also reported. The coordination around the metal atoms in the solid state is best described as distorted octahedra. The two chelating DHA ligands define an equatorial plane and the axial positions are occupied by two monodentate DMSO ligands coordinated by oxygen atoms, in the trans,trans,trans configuration. Significant differences were found between the Cd and Zn coordination spheres, with the latter forming relatively looser octahedral complexes.     

Synthesis and properties of cyclic gomesin and analogues

Gomesin (Gm) was the first antimicrobial peptide (AMP) isolated from the hemocytes of a spider, the Brazilian mygalomorph Acanthoscurria gomesiana. We have been studying the properties of this interesting AMP, which also displays anticancer, antimalarial, anticryptococcal and anti‐Leishmania activities. In the present study, the total syntheses of backbone‐cyclized analogues of Gm (two disulfide bonds), [Cys(Acm)^2,15]‐Gm (one disulfide bond) and [Thr^2,6,11,15,d ‐Pro⁹]‐Gm (no disulfide bonds) were accomplished, and the impact of cyclization on their properties was examined. The consequence of simultaneous deletion of pGlu¹ and Arg¹⁶‐Glu‐Arg¹⁸‐NH₂ on Gm antimicrobial activity and structure was also analyzed. The results obtained showed that the synthetic route that includes peptide backbone cyclization on resin was advantageous and that a combination of 20% DMSO/NMP, EDC/HOBt, 60 °C and conventional heating appears to be particularly suitable for backbone cyclization of bioactive peptides. The biological properties of the Gm analogues clearly revealed that the N‐terminal amino acid pGlu¹ and the amidated C‐terminal tripeptide Arg¹⁶‐Glu‐Arg¹⁸‐NH₂ play a major role in the interaction of Gm with the target membranes. Moreover, backbone cyclization practically did not affect the stability of the peptides in human serum; it also did not affect or enhanced hemolytic activity, but induced selectivity and, in some cases, discrete enhancements of antimicrobial activity and salt tolerance. Because of its high therapeutic index, easy synthesis and lower cost, the [Thr^2,6,11,15,d ‐Pro⁹]‐Gm analogue remains the best active Gm‐derived AMP developed so far; nevertheless, its elevated instability in human serum may limit its therapeutic potential. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Sodium and potassium fluxes and compartmentation in roots of atriplex and oat

K⁺ and Na⁺ fluxes and ion content have been studied in roots of Atriplex nummularia Lindl. and Avena sativa L. cv Goodfield grown in 3 millimolar K⁺ with or without 3 or 50 millimolar NaCl. Compartmental analysis was carried out with entire root systems under steady-state conditions.

Increasing ambient Na⁺ concentrations from 0 to 50 millimolar altered K⁺, in Atriplex, as follows: slightly decreased the cytoplasmic content (Q_c), the vacuolar content (Q_v), and the plasma membrane influx and efflux. Xylem transport for K⁺ decreased by 63% in Atriplex. For oat roots, similar increases in Na⁺ altered K⁺ parameters as follows: plasma membrane influx and efflux decreased by about 80%. Q_c decreased by 65%, and xylem transport decreased by 91%. No change, however, was observed in Q_v for K⁺. Increasing ambient Na⁺ resulted in higher (3 to 5-fold) Na⁺ fluxes across the plasma membrane and in Q_c of both species. In Atriplex, Na⁺ fluxes across the tonoplast and Q_v increased as external Na⁺ was increased. In oat, however, no significant change was observed in Na⁺ flux across the tonoplast or in Q_v as external Na⁺ was increased. In oat roots, Na⁺ reduced K⁺ uptake markedly; in Atriplex, this was not as pronounced. However, even at high Na⁺ levels, the influx transport system at the plasma membrane of both species preferred K⁺ over Na⁺.

Based upon the Ussing-Teorell equation, it was concluded that active inward transport of K⁺ occurred across the plasma membrane, and passive movement of K⁺ occurred across the tonoplast in both species. Na⁺, in oat roots, was actively pumped out of the cytoplasm to the exterior, whereas, in Atriplex, Na⁺ was passively distributed between the free space, cytoplasm, and vacuole.

     

Engineering of caseins and modulation of their structures and interactions

β-Casein (β-CN) is a milk protein widely used in food industries because of its mild emulsifying properties due to its amphiphilicity. However, the elements determining its micellization behavior in solution and interfacial behavior at the air–water interface are not well known. In order to study how the forced dimerisation influences functional properties of β-CN, recombinant wild-type β-CN was produced and distal cysteinylated forms of recombinant β-CN were engineered. We show that 1) cysteinylated β-CN formed mainly dimers bridged by disulfide bonds; 2) the process of dimerization adds to the micellization process with temperature and is poorly reversible; 3) covalent disulfide linkage forms at the air–water interface at a lower temperature than in bulk. In conclusion, the location of the cysteinylation in the C-terminus or N-terminus or both is of importance for the properties of β-CN.     

Impact of Transport Crate Reuse and of Catching and Processing on Campylobacter and Salmonella Contamination of Broiler Chickens

The influence of transport, catching, and processing on contamination of broiler chickens with Salmonella and Campylobacter was investigated. Transport crates were reused with high frequency and were often still contaminated with Salmonella and Campylobacter when they arrived at the farm despite the fact that they were washed at the factory, and thus they were a potential route of infection. These organisms contaminated the feathers of previously Campylobacter- and Salmonella-negative birds going to the processing plant and were isolated from processed carcasses, albeit at a low frequency. The Campylobacter types which were the predominant organisms on the live birds when they arrived at the processing plant were not necessarily the types that were most frequently isolated from processed carcasses. This finding may reflect cross-contamination that occurred during processing or differences in the tolerance of the strains to the hostile environments that the bacteria experienced. The process of catching and putting the birds in crates significantly increased the chance of contamination with Campylobacter (P < 0.001).     

Composition and properties of wood and cellulose of tropical plants

A component, chemical and morphological composition of wood of the Howea fosteriana palm and the Cereus peruvians cactus and the wood stem of the Dracaena sanderiana was studied. The supramolecular structure and the physicochemical properties of cellulose samples which were extracted from the wood species were examined by wide-angle X-ray scattering, Fourier transform infrared spectroscopy, high-resolution ¹³CP/MAS nuclear magnetic resonance in a solid state, and scanning electron microscopy.     

The preparation and characterization of potassiumtriisobutyldialuminum and tripotassiumdecaisobutylpentaaluminum

The reaction between Al₂ⁱBu₄ and K results in the formation of KⁱBu and KAl₂ⁱBu₃. The latter reacts with additional K to produce K₃Al₅ⁱBu₁₀. The oxidation states of aluminum, associated with these reduced aluminum compounds, have been determined by oxidative hydrolyses. Spectroscopic characterization included infrared and NMR data; ¹H,¹³C,²⁷Al, and ³⁹K.     

Effects of lanthanum and cerium on the growth and mineral nutrition of corn and mungbean

Background and Aims: Plant growth responses to the rare earth elements lanthanum(La) and cerium (Ce) have been reported, but little is knownabout the effects of these two elements on plant mineral nutrition. Methods: Corn (Zea mays ‘Hycorn 82’) and mungbean (Vignaradiata ‘Berken’) were grown in continuous flowingnutrient solutions containing 0, 0·2, 1·0 and5·0 µM La or Ce. At harvest plants were dividedinto roots and shoots, dried, weighed and analysed for macro-and micronutrients, as well as for La and Ce. Key Results: La and Ce did not increase the growth of corn or mungbean. Thedry weight of corn shoots was decreased by 32 % in the presenceof 5·0 µM Ce; the other La and Ce concentrationshad no effect. La and Ce concentrations of 0·9 and 5·0µM decreased the shoot dry weight of mungbean by 75 or95 %, the two elements having closely similar effects. Decreasesin the uptake of Ca, Na, Zn and Mn by corn were observed withincreases in solution La and Ce. For mungbean, the uptake ratesof all measured elements decreased with increases in solutionLa and Ce. The concentrations of La and Ce in the roots of bothspecies were higher than in the shoots and increased stronglywith increasing concentrations of La or Ce in solution. TheLa and Ce concentrations in mungbean shoots were always higherthan in corn shoots. Conclusions: La and Ce did not enhance the growth of corn or mungbean, butdecreased the growth, root function and consequently the nutritionalstatus of mungbean at concentrations >0·2 µMin solution. It is concluded that if La or Ce have positiveeffects on corn and mungbean growth, they can only occur atsolution concentrations below 0·2 µM.     

Systematics of Serinus canaries and the status of Cape and Yellow-crowned Canaries inferred from mtDNA and morphology

The taxonomy of, and phylogenetic relationships among, African canaries typically assigned to the genus Serinus sensu lato (including the putative genera Alario, Pseudochloroptila, Serinops, Ochrospiza, Dendrospiza and Crithagra) were investigated, based on 823bp of the mitochondrial cytochrome b gene. Two clades emerged: (1) Palaearctic and Afrotropical taxa, including Serinus serinus, S. canaria, A. alario and the S. canicollis complex (S. c. canicollis, thompsonae and flavivertex), and (2) taxa endemic to the Afrotropics comprising Pseudochloroptila, Serinops, Ochrospiza, Poliospiza, Dendrospiza, Poliospiza and Crithagra spp. However, only clade one has jackknife and bootstrap support values above 50. The two clades were separated by Carduelis taxa, suggesting that Serinus sensu lato is not monophyletic. As it stands, the phylogeny does not support the recognition of Alario and Serinops and possibly Ochrospiza, Dendrospiza and Pseudochloroptila (Cape siskins) as distinct genera. Alario is sister to Serinus canicollis whereas the others are intermingled in a clade comprised primarily by Crithagra spp. The use of Serinus is confined to the Palaearctic canaries and allied species, and Crithagra for the strictly Afrotropical clade. Since the cytochrome b sequence divergence between the allopatric Cape (S. [c.] canicollis) and Yellow-crowned (S. [c.] flavivertex) canaries (2.8%) was similar to differences between other closely-related species and there are marked plumage differences between these taxa, we suggest that they be elevated to full species rank.