Screening rough-seeded lupins (Lupinus pilosus Murr. and Lupinus atlanticus Glads.) for tolerance to calcareous soils

Soil- and solution-based screening methods were used to identify interspecific and intraspecific variation in lupins for tolerance to calcareous soils. Plants were grown for 21 days in a calcareous soil (pH 8.2; 50% CaCO₃; moisture content 90% of field capacity) for soil-based screening and in nutrient solution containing 15 mM KHCO₃ for solution-based screening. Chlorosis as an indicator of tolerance was recorded. Lupinus pilosus Murr. had the most tolerant genotypes and had the greatest range of intraspecific variation. Most genotypes of Lupinus atlanticus Glads. and Lupinus angustifolius L. were moderately intolerant, although two genotypes of L. atlanticus appeared to be tolerant. Lupinus albus L. had moderately tolerant to moderately intolerant genotypes, whilst the single genotypes of Lupinus cosentinii Guss. and Lupinus digitatus Forsk. appeared tolerant. In a field study six genotypes of L. pilosus identified in the soil-based screening as differing in their tolerance to the calcareous soil were grown on comparable calcareous (pH 8.3; topsoil 3% CaCO₃, subsoil 13% CaCO₃) and non-calcareous (pH 7.3) soils within a paddock. Chlorosis and nutrient concentrations in the youngest leaves were measured 53 days after sowing, whilst grain yield was estimated at harvest. Despite the soil containing a much lower CaCO₃ content than used in the screening method, the field study confirmed that moderately intolerant to intolerant genotypes had lower relative grain yields than more tolerant genotypes. Chlorosis rankings of the genotypes were correlated between field and the screening studies. It is suggested that the incorporation of genes conferring tolerance to calcareous soils into high yielding, agronomically suitable genotypes of L. pilosus should be an important objective in a lupin breeding program for calcareous soils.     

Senescence and protein remobilisation in leaves of maturing wheat plants grown on waterlogged soil

Nicotianamine (NA), the key precursor of the mugineic acid family phytosiderophores (MAs), is synthesized from S-adenosylmethionine (SAM). The NA synthase was strongly induced by Fe-deficiency treatment, and the activity increased to the maximum level faster than the time of maximum level of MAs secretion and also before the appearance of severest chlorosis. The enzyme was mainly localized in the roots of barley. NA synthase had the optimum pH at 9.0, a molecular weight of about 40,00050,000 estimated by gel filtration or about 30,000 by SDS-PAGE. Using hydrophobic chromatography, hydroxylapatite chromatography, and preparative SDS-PAGE, NA synthase was purified as one band on SDS-PAGE.     

Characterization of phytosiderophore secretion under Fe deficiency stress in Festuca rubra

In the present study we investigated the response to iron (Fe) deficiency in two cultivars of Festuca rubra L. (Rubina and Barnica) used in correction of chlorosis of fruit trees cultivated on calcareous soils. We found that a Fe-chelating compound, identified as 2-deoxymugineic acid (DMA), was secreted from the roots in response to Fe-deficiency in both cultivars. The amount of DMA secreted into solution increased with the development of Fe-deficiency. The secretion showed a distinct diurnal rhythm characterized by a secretion peak at between 2 and 5 hours after sunrise at 20°C. However, this secretion peak was delayed by 3 hour at low temperature (<10°C) and occurred 3 h earlier at high temperature (30°C). When water used for the collection of root exudates was pre-warmed (25°C) or pre-cooled (10°C), this led to an earlier or a delayed secretion compared to control (15°C) under the same air temperature, respectively. Short-term shading treatment did not affect the secretion pattern of DMA. These results demonstrate that the secretion time of DMA from the roots is, at least partly controlled by the temperature in the root environment. Overall, these findings suggest that the ability of Festuca rubra to prevent Fe chlorosis symptoms (`re-greening effect') of associated fruit trees is partially related to the secretion of DMA which increase Fe availability in calcareous soils.     

Absolute measurement of cell expansion in plant cell suspension cultures

A method is described for the measurement of intracellular volume (V_i) in cell cultures. In principle, any stable compound that neither penetrates the plasma membrane nor binds to the cells can be used to trace the total extracellular (apoplastic) volume and hence to estimate the intracellular volume. No suitable coloured or UV-absorbing compound could be found among those tested; the main problems were binding to the cell surface and/or instability in the medium. However, [¹⁴C]mannitol was an acceptable apoplastic marker, by use of which we showed that 21–47% of total packed cell volume (PCV) was intracellular, and 14–33% of total settled cell volume (SCV) was intracellular. Therefore, measurements of PCV and SCV misrepresent cell expansion to a variable extent. Cultures of Acer, Rosa, Spinacia and Zea achieved final symplastic volumes of only 9, 14, 6 and 6%, respectively, of the total suspension culture volume.     

Release of carboxylic anions and protons by tomato roots in response to ammonium nitrate ratio and pH in nutrient solution

The exudation of certain organic anions and protons by roots which may affect solubility of metals and P and uptake by plants, is affected by nitrogen form and pH. The objective of this work was to study exudation of carboxylates and H⁺/OH^– by tomato plants in response to NH₄/NO₃ ratio and pH in nutrient solution. Four NH₄/(NH₄+NO₃) ratios (R= 0, 0.33, 0.67 and 1) and constant vs. variable solution pH treatments were investigated. The sum of the exudation rates of all carboxylates tended to decline with increasing R, particularly tri- and dicarboxylates. The molar fraction of the exuded tri- and dicarboxylates, averaged over all treatments and plant ages, increased in the order tartarate 2%), malate (6%), succinate (15%), citrate (26%) and fumarate (46%). At R=1 the solution pH dropped from 5.2 to 3 and at R=0 increased to 8. The R corresponding to the pH stat of tomato plant was 0.3. For the constant solution pH treatment, the effect of solution pH on carboxylate exudation rate was small as compared to the effect of R. The exudation of citrate and H⁺ efflux which were initiated when NO₃ and NH₄ uptake rates per plant exceeded certain threshold values, increased with plant age.     

Correlation between 15N NMR chemical shifts in proteins and secondary structure

Summary An empirical correlation between the peptide ¹⁵N chemical shift, ¹⁵N_i, and the backbone torsion angles _i, _i–1 is reported. By using two-dimensional shielding surfaces (_i1–1), it is possible in many cases to make reasonably accurate predictions of ¹⁵N chemical shifts for a given structure. On average, the rms error between experiment and prediction is about 3.5 ppm. Results for threonine, valine and isoleucine are worse (4.8 ppm), due presumably to ₁-distribution/-gauche effects. The rms errors for the other amino acids are 3 ppm, for a typical maximal chemical shift range of 15–20 ppm. Thus, there is a significant correlation between ¹⁵N chemical shift and secondary structure.     

Identification of restriction fragment length polymorphisms linked to genes controlling soluble solids content in tomato fruit

Summary Gene(s) conferring high soluble solids (SS) in tomato fruit had been backcrossed previously from a wild tomato species, Lycopersicon chmielewskii LA1028 ( 10% SS), into a L. esculentum cultivar, VF36 ( 5% SS), to derive a BC₅S₅ line, LA1563, similar to VF 36 but with 7–8% SS. DNAs from these lines and a tomato breeding line, H2038, were screened for restriction fragment length polymorphisms (RFLPs) using four restriction endonucleases and sixty clones chosen at random from a tomato cDNA library. Most of the cDNA clones (56) identified the same RFLP in VF 36 and LA1563 and a different RFLP in LA1028. However, two cDNA clones identified the same RFLP in LA1563 and LA1028 and a different RFLP in VF36. To determine whether RFLPs identified by these two cDNA clones were linked to SS genes, a H2038 x LA1563 F₂ population was screened for segregation of the RFLPs and for SS content. The segregation ratios of these RFLPs were consistent with ratios expected for codominant alleles at unlinked loci. Analysis of variance of SS content for different RFLP genotypic classes indicated that RFLP alleles at one of the loci were linked to genes controlling SS content. The RFLP allele from the high SS tomato line, LA1563, was associated with significantly higher SS content and, therefore, could be useful in selecting for high SS gene(s) in a tomato breeding program.     

An analysis of flash-induced electrical transients of a BLM containing chloroplast lamella extracts

Summary The electrical transients produced by chloroplast bilayer lipid membranes (Chl-BLM) from flash excitation are seen to result from three photocurrents and a discharge current. Each of the three photo-initiated charge transports in Chl-BLM (designated as Components A, B and C) exhibits an action spectrum similar to chlorophyll absorption spectra. The fast components (A and B), which are induced by electron acceptors such as Fe⁺³, have rise-times of 3 sec and 20 msec, and occur in TLM (thin lipid membranes, i.e., colored membranes up to 1 thick) as well as in BLM. Component C is induced by a transmembrane pH difference or applied voltage, has a rise-time of 1 sec, and occurs only in BLM. Component C is associated with exciton dissociation and proton transport. The mobility of the Component A current carriers in TLM is estimated to be about 1×10^–2 cm²/volt sec, and are, hence,electronic. The photovoltage waveforms are described by equations developed, which consider Component A as being caused by a direct charge separation proportional to the illumination intensity (within 0.5 sec), and Components B and C being caused by two types of exciton processes which cause charge transport after the illumination period.     

Gene-sized DNA molecules of the macronuclei in three species of hypotrichs: Size distributions and absence of nicks

Macronuclear DNAs from three related hypotrichous ciliated protozoans were compared by agarose gel electrophoresis. Each was shown to be composed of DNA duplexes that yielded a unique pattern of bands overlying a continuous distribution of DNA sizes ranging from 400 bp to 20,000 bp. By EM, the number average molecular sizes for doublestranded DNA were 2,200 bp for Oxytricha sp., 2,514 bp for Stylonychia pustulata and 1,836 bp for Euplotes aediculatus. Contrary to previous reports we present evidence that the macronuclear DNAs in each of these three organisms lack single-stranded interruptions.     

Heterogeneity of calcium compartmentation: Electron probe analysis of renal tubules

Summary The objective of this study has been to determine the intracellular localization of calcium in cryofixed, cryosectioned suspensions of kidney proximal tubules using quantitative electron probe X-ray microanalysis. Two populations of cells have been identified: 1) Viable cells, representing the majority of cells probed, are defined by their relatively normal K/Na concentration ratio of 41. Their measured Ca content is 4.1±1.4 (sem) mmol/kg dry wt in the cytoplasm and 3.1 ± 1.1 mmol/kg dry wt in the mitochondria, or an average cell calcium content of 3.8 mmol/kg dry wt. 2) Nonviable cells, defined by the presence of dense inclusions in their mitochondria and a K/Na concentration ratio of 1. The Ca content is 15±2 mmol/kg dry wt in the cytoplasm and 685±139 mmol/kg dry wt in the mitochondria of such cells. Assuming 25 to 30% of the cell volume is mitochondrial, the overall calcium content of such nonviable cells is 210 mmol/kg dry wt. The presence of these inclusions in 4 to 5% of the cells would account for the average total Ca content measured in perchloric acid extracts of isolated proximal tubule suspensions ( 18 nmol/mg protein or 12.6 mmol/kg dry wt). Whole kidney tissues display a large variability in toal Ca content (4.5 to 18 nmol/mg protein, or 3.4 to 13.5 mmol/kg dry wt), which could be accounted for by inclusion in 0 to 4% of the cells. The electron probe X-ray microanalysis (EPXMA) data conclusively demonstrate that thein situ mitochondrial Ca content of viable cells from the kidney, proximal tubule is low and support the idea that mitochondrial Ca may regulate dehydrogenase activity but probably does not normally control cytosolic free Ca.     

Changes in gill histology of fathead minnows and yellow perch transferred to soft water or acidified soft water with particular reference to chloride cells

Summary Fathead minnows, Pimephales promelas, and yellow perch, Perca flavescens, were transferred from moderately soft Lake Superior water (hardness 45mg/l as CaCO₃) to very soft diluted Lake Superior water (hardness 4.5mg/l). Sulfuric acid was added in some treatments by means of a multichannel diluter. In very soft water, chloride cells proliferated in the gills, especially in the epithelium of the secondary lamellae. When exposed to acid, chloride cells were damaged and less abundant in the secondary lamellae, and blood osmolality was reduced at pH 5.0 (x = 188 mOsm/kg, 9 days exposure; normal 280 mOsm/kg) for the minnows and pH 4.1 (x = 218 mOsm/kg, 58 days exposure; normal 329 mOsm/kg) for the perch. Certain chloride cells which form gland-like clusters in the primary lamellae of perch gills showed little damage even at pH 4.1. The present study supports the view that chloride cells proliferate in very soft fresh water to help maintain ionic balances, and that damage to these cells in acidified soft water may be related to diminished ionoregulatory capacity. The greater acid tolerance of chloride cells of, and the higher blood osmolality maintained by, perch could help to explain the greater tolerance of this species to low pH. In some cases, a species' ability to acclimate to very soft water and acidified soft water may depend upon the number, distribution, and physiology of its chloride cells.     

Function of the hemoglobin and the gas bubble in the backswimmerAnisops assimilis (Hemiptera: Notonectidae)

Summary The presence of hemoglobin inAnisops assimilis has been demonstrated to be a vital factor in the physiology of this organism. The hemoglobin is composed of heterogeneous subunits which aggregate upon deoxygenation. This association-dissociation equilibrium confers a steep gradient (n _H6) to the oxygen equilibrium curve and a low oxygen affinity (P ₅₀40 mmHg). Oxygen bound by the hemoglobin is released into a gas bubble enabling the bug to regulate its density around that of water. Thus, energy is conserved during a dive, allowing the animal to remain in mid-water for long periods. This adaptive feature has facilitated the exploitation of an ecological niche available to few other organisms.     

Scanning electron-microscopic study on the three-dimensional structure of motor endplates of the slow (tonic) muscle fibers in the frog,Rana n. nigromaculata

Summary The three-dimensional organization of the motor endplates of the slow fibers of the rectus abdominis muscle in the Japanese meadow frog (Rana nigromaculata nigromaculata Hallowell) is visualized by use of a field-emission scanning electron microscope after removal of connective tissue components by HCl hydrolysis. Clusters of shallow oval depressions 1–3 m in diameter are seen in the postsynaptic membrane at intervals of about 150 m. On the surface of these depressions, a few low bulges of postsynaptic membrane are irregularly arranged. Terminal boutons, 1–3 m in diameter, occur along the length of nerve branches and terminals and fit into the shallow oval depressions of the postsynaptic membrane. The Schwann cells covering the terminal branches exhibit a simpler organization than those in twitch fibers.     

A physiological study ofTeucrium scorodonia ecotypes which differ in their susceptibility to lime-induced chlorosis and iron-deficiency chlorosis

Summary Edaphic ecotypes ofTeucrium scorodonia have been shown which differ in their susceptibility to lime-induced chlorosis. Plants especially resistant or susceptible to lime-induced chlorosis were found to be similarly resistant or susceptible to iron-deficiency chlorosis. Differences were found in the chlorophyll-iron and dry weight-chlorophyll relationships of the leaves of green and chloroticTeucrium plants, similar effects being produced by growth on a calcareous soil, in iron-deficient culture or by bicarbonate treatment. Chlorotic leaves had less chlorophyll per unit iron but had a greater dry weight per unit chlorophyll than green material. Chlorotic leaves were found to be reduced in both leaf area and dry weight compared with green ones, the reduction in dry weight being the greatest. Common root abnormalities were noted in chlorotic material induced by the above three methods.Evidence was produced which suggested that the difference between chlorosis-resistant and susceptible plants lay in qualitative differences in their iron transport compounds produced within the rootstock. Differential iron uptake was not suggested as a cause of the differences in behaviour. There was, however, evidence of a key role of the root iron pool in population differences in chlorosis susceptibility.Bicarbonate was found to suppress first iron uptake and then iron translocation. A possible causal role of the bicarbonate ion in lime-induced chlorosis was suggested through these effects and through its possible effect on the production of iron-transport compounds.     

Long link induction between the microtubules of the manchette in intermediate stages of spermiogenesis

Summary Links unusual for their length and variable morphology have been described between manchette microtubules in late stages of rat spermiogenesis. In earlier stages of rat spermiogenesis obvious links longer than 160 Å are rare, the majority being 80 or 120 Å in length. The most easily discernible geometric pattern in cross-sections of assemblies of manchette microtubules in intermediate stages of rat spermiogenesis is that of linear arrays sometimes resulting in long and irregularly folded chains of closely linked microtubules. Colcemid disrupts these arrays and is responsible for the formation of more complex geometric patterns. Six hours after drug administration the manchette is dramatically reduced in length. Sheet-like links of variable dimensions and >160 Å in length interconnect not only microtubules but C-type microtubules as well as other links. These links are similar in morphology to those found in later stages of rat spermiogenesis. It is suggested that the formation of these links may perhaps be dependent upon aspects of microtubule disassembly.Supported by a grant to E. A. MacKinnon by the Medical Research Council of Canada.     

Significance of rooting depth in mire plants: Evidence from natural <Superscript>15</Superscript>N abundance

Variation in stable nitrogen isotope ratios (¹⁵N) was assessed for plants comprising two wetland communities, a bog-fen system and a flood plain, in central Japan. ¹⁵N of 12 species from the bog-fen system and six species from the flood plain were remarkably variable, ranging from –5.9 to +1.1 and from +3.1 to +8.7, respectively. Phragmites australis exhibited the highest ¹⁵N value at both sites. Rooting depth also differed greatly with plant species, ranging from 5cm to over 200cm in the bog-fen system. There was a tendency for plants having deeper root systems to exhibit higher ¹⁵N values; plant ¹⁵N was positively associated with rooting depth. Moreover, an increasing gradient of peat ¹⁵N was found along with depth. This evidence, together with the fact that inorganic nitrogen was depleted under a deep-rooted Phragmites australis stand, strongly suggests that deep-rooted plants actually absorb nitrogen from the deep peat layer. Thus, we successfully demonstrated the diverse traits of nitrogen nutrition among mire plants using stable isotope analysis. The ecological significance of deep rooting in mire plants is that it enables those plants to monopolize nutrients in deep substratum layers. This advantage should compensate for any consequential structural and/or physiological costs. Good evidence of the benefits of deep rooting is provided by the fact that Phragmites australis dominates as a tall mire grass.     

New expanded bed adsorbents for the recovery of DNA

A 20–40 m pellicular high density (3.7 g cm^–3) expanded bed material has been designed for the capture of DNA and other large macromolecules. Anion exchangers fashioned out of these supports exhibited dramatically enhanced DNA binding capacities over commercial anion exchange adsorbents (6 mg ml^–1, c.f. 50 g ml^–1 at 10% breakthrough), due to a combination of small particle and fuzzy surface architecture created through the coupling of polyethylene imine chains.     

Effects of soil temperature on root and shoot growth traits and iron deficiency chlorosis in sorghum genotypes grown on a low iron calcareous soil

Iron deficiency chlorosis (FeDC) is a common disorder for sorghum [Sorghum bicolor (L.) Moench] grown on alkaline calcareous soils. Four sorghum genotypes were grown in growth chambers on a low Fe (1.3 g/g DTPA-extractable), alkaline (pH 8.0), calcareous (3.87% CaCO₃ equivalent) Aridic Haplustoll to determine effects of different soil temperatures (12, 17, 22 and 27°C at a constant 27°C air temperature) on various root and shoot growth traits and development of FeDC. As soil temperature increased, leaf chlorosis became more severe, and shoot and root dry weights, root lengths, and leaf areas increased markedly. Shoot/root ratios, shoot weight/root length, leaf area/shoot weight and leaf area/root weight and root length also increased while root length/root weight decreased as soil temperature increased. Severe FeDC developed in all genotypes even though genotypes had previously shown different degrees of resistance to FeDC. Genotypes differed in most growth traits, especially dry matter yields, root lengths, and leaf areas, but most traits did not appear to be related to genotype resistance to FeDC. The most FeDC resistant genotype had the slowest growth rate and this may be a mechanism for its greater resistance to FeDC.     

Induction of changes in the secondary structure of globular proteins by a hydrophobic surface

Circular dichroism, ellipsometry and radiolabeling techniques were employed to study the induction of changes in the secondary structure of BSA, myoglobin and cytochrome C by a hydrophobic surface. The results showed that adsorbed protein molecules lose their ordered native structure in the initial stage of adsorption and the structure appears to be a random or disordered conformation. Protein molecules adsorbed in later stages adopt a more ordered secondary structure ( helix and structure). The changes of secondary structure of globular proteins induced by a hydrophobic surface can be explained by the steric interaction between adsorbed proteins as well as by hydrophobic interactions during the adsorption process. In addition, there is obviously an intermediate stage in which the protein molecules are mainly in the structure, indicating that for certain proteins, the structure may be a more stable secondary structure than helix on the hydrophobic surface. Correspondence to: S.-F. Sui     

Altitudinal distribution of first-year male Black Redstarts(Phoenicurus ochruros) in the western Pyrenees

Summary First-year, Black Redstart- in brown plumage were found to breed above tree-line in the western Pyrenees. Significantly more brown than black (adult) ones bred at higher than at lower altitudes. It is suggested that adult establish territories at lower altitudes, thereby forcing younger birds to settle higher up the slopes.

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Zusammenfassung Höhenverbreitung einjähriger Hausrotschwanz- in den Westpyrenäen. — Einjährige braune des Hausrotschwanzes wurden als Brutvögel oberhalb der Baumgrenze in den Westpyrenäen festgestellt. Im Vergleich brüteten signifikant mehr braune als schwarze (=ad.) in größeren Höhen. Vermutlich besetzen ad. Reviere in niedrigeren Höhenstufen und zwingen so jüngere Vögel, sich in größeren Meereshöhen anzusiedeln.