Soil acidification as caused by the nitrogen uptake pattern of Scots pine (Pinus sylvestris)

Three-year-old Scots pine (Pinus sylvestris) trees were grown on a sandy forest soil in pots, with the objective to determine their NH₄/NO₃ uptake ratio and proton efflux. N was supplied in three NH₄-N/NO₃-N ratios, 3:1, 1:1 and 1:3, either as ¹⁵NH₄+¹⁴NO₃ or as ¹⁴NH₄+¹⁵NO₃. Total N and ¹⁵N acquisition of different plant parts were measured. Averaged over the whole tree, the NH₄/NO₃ uptake ratios throughout the growing season were found to be 4.2, 2.5, and 1.5 for the three application ratios, respectively. The excess cation-over-anion uptake value (C_a-A_a) appeared to be linearly related to the natural logarithm of the NH₄/NO₃ uptake ratio. Further, this uptake ratio was related to the NH₄/NO₃ ratio of the soil solution. From these relationship it was estimated that Scots pine exhibits an acidifying uptake pattern as long as the contribution of nitrate to the N nutrition is lower than 70%. Under field circumstances root uptake may cause soil acidification in the topsoil, containing the largest part of the root system, and soil alkalization in deeper soil layers.     

Root-zone temperature and salinity: Interacting effects on tillering,growth and element concentration in barley

The effects of root-zone salinity (0, 30, and 60 mmol L^–1 of NaCl) and root-zone temperature (10, 15, 20, and 25°C) and their interactions on the number of tillers, total dry matter production, and the concentration of nutrients in the roots and tops of barley (Hordeum vulgare L.) were studied. Experiments were conducted in growth chambers (day/night photoperiod of 16/8 h and constant air temperature of 20°C) and under water-culture conditions. Salinity and root temperature affected all the parameters tested. Interactions between salinity and temperature were significant (p<0.05) for the number of tillers, growth of tops and roots, and the concentration of Na, K, P in the tops and the concentration of P in the roots. Maximum number of tillers and the highest dry matter were produced when the root temperature was at the intermediate levels of 15 to 20°C. Effect of salinity on most parameters tested strongly depended on the prevailing root temperature. For example, at root temperature of 10°C addition of 30 mmol L^–1 NaCl to the nutrient solution stimulated the growth of barley roots; at root temperature of 25°C, however, the same NaCl concentration inhibited the root growth. At 60 mmol L^–1, root and shoot growth were maximum when root temperature was kept at the intermediate level of 15°C; most inhibition of salinity occurred at both low (10°C) and high (25°C) root temperatures. As the root temperature was raised from 10 to 25°C, the concentration of Na generally decreased in the tops and increased in the roots. At a given Na concentration in the tops or in the roots, respective growth of tops or roots was much less inhibited if the roots were grown at 15–20°C. It is concluded that the tolerance of barley plant to NaCl salinity of the rooting media appears to be altered by the root temperature and is highest if the root temperature is kept at 15 to 20°C.     

INTERACTIONS BETWEEN KURIL SEALS AND SALMON TRAP NET FISHERY IN THE COASTAL WATERS OF SOUTHEASTERN HOKKAIDO

An annual average of 163 Kuril seals was found dead in two years in salmon trap nets along the coastal waters of the Nemuro Peninsula and adjacent areas. The seal-caused damage to the total salmon catch at the salmon trap nets was concentrated in some of them, particularly No. 27, where seals killed or injured 5.1% of the catch in 1982, and 1.8% in 1983. Based on the proportion of Kuril seals among the dead seals in the trap nets, it was estimated that Kuril seals damaged 4.7% of the total salmon catch at No. 27 in 1982, and 1.7% in 1983. Not all seals that entered the trap net drowned; some killed or damaged salmon, and then escaped.     

Comparison of the crystal structure of bacteriophage T4 lysozyme at low, medium, and high ionic strengths

Crystals of bacteriophage T4 lysozyme used for structural studies are routinely grown from concentrated phosphate solutions. It has been found that crystals in the same space group can also be grown from solutions containing 0.05 M imidazole chloride, 0.4 M sodium choride, and 30% polyethylene glycol 3500. These crystals, in addition, can also be equilibrated with a similar mother liquor in which the sodium chloride concentration is reduced to 0.025 M. The availability of these three crystal variants has permitted the structure of T4 lysozyme to be compared at low, medium, and high ionic strength. At the same time the X-ray structure of phage T4 lysozyme crystallized from phosphate solutions has been further refined against a new and improved X-ray diffraction data set. The structures of T4 lysozyme in the crystals grown with polyethylene glycol as a precipitant, regardless of the sodium chloride concentration, were very similar to the structure in crystals grown from concentrated phosphate solutions. The main differences are related to the formation of mixed disulfides between cysteine residues 54 and 97 and 2-mercaptoethanol, rather than to the differences in the salt concentration in the crystal mother liquor. Formation of the mixed disulfide at residue 54 resulted in the displacement of Arg-52 and the disruption of the salt bridge between this residue and Glu-62. Other than this change, no obvious alterations in existing salt bridges in T4 lysozyme were observed. Neither did the reduction in the ionic strength of the mother liquor result in the formation of new salt bridge interactions. These results are consistent with the ideas that a crystal structure determined at high salt concentrations is a good representation of the structure at lower ionic strengths, and that models of electrostatic interactions in proteins that are based on crystal structures determined at high salt concentrations are likely to be relevant at physiological ionic strengths.     

Chirality of reverse micelles

Four chiral analogues of the surfactant Aerosol-OT (AOT) have been synthesized and characterized. All of them form reverse micelles in apolar solvents in the w₀ range 0–30 (w₀ = [water]/[tenside]). Reverse micellar solutions have been investigated by UV absorption and circular dichroism spectroscopies with the aim of clarifying whether the formation of the macromolecular micellar structure induces the appearance of new chromophoric bands or perturbs the existing ones. Methanolic solutions of the surfactants, in which no micellar aggregates are formed, were taken as references. One of the products 1(S),1′(S)-dimethylbisheptylsulphosuccinate sodium salt (MH-AOT) was capable of forming reverse micelles of relatively high water content (w₀ up to 40) and this process was accompanied by a specific increase in the intensity of the circular dichroism band associated with the ester absorbance of the molecule. As no concomitant changes were seen in the UV absorbance spectrum, it was concluded that this observation reflected conformational events occurring within the surfactant rather than chromophoric perturbation. These results are qualitatively similar to those found recently for lecithin reverse micelles which, however, form gels at sufficiently high water contents. The chiroptical properties of these supramolecular aggregates are compared with those of covalent macromolecular systems such as polypeptides.     

3D structure of bovine pancreatic ribonuclease A in aqueous solution: An approach to tertiary structure determination from a small basis of1H NMR NOE correlations

Summary A method is proposed to generate initial structures in cases where the distance geometry method may fail, such as when the set of¹H NMR NOE-based distance constraints is small in relation to the size of the protein. The method introduces an initial correlation between the and backbone angles (based on empirical observations) which is relaxed in later stages of the calculation. The obtained initial structures are refined by well-established methods of energy minimization and restrained molecular dynamics. The method is applied to determine the solution structure of Ribonuclease A (124 residues) from a NOE basis consisting of 467 NOE cross-correlations (97 intra-residue, 206 sequential, 23 medium-range and 141 long-range) obtained at 360 MHz. The global shape and backbone overall fold of the eight final refined structures are close to those shown by the crystal structure. A meaningful difference in the positioning of the catalytically important His¹¹⁹ side chain in the solution and crystal structures has been detected.     

Comparative limnology of Sambhar and Didwana lakes (Rajasthan,NW India)

Two alkaline saline inland lakes of Indian arid region were studied during 1984 and 1985, to assess functioning and interaction of various environmental and biological factors. Changes in physical and chemical variables, planktonic composition, chlorophyll content and phytoplankton primary productivity were examined.Salinity in both lakes fluctuated from almost fresh water (1.80), to hypersaline (300) and acted as the main controlling factor for almost all the biotic parameters. Maximum total alkalinities were 2162 mg l^–1 and 2090 mg l^–1, respectively in Sambhar and Didwana lakes. Dissolved oxygen ranged from completely anoxic conditions to maxima of 11.68 and 7.29 mg 1^–1, respectively in Sambhar and Didwana lakes. Nutrient enrichment in the lakes was low.The phytoplankton species composition of Sambhar lake was reduced from an earlier reported 20 genera to only 11 (Nostoc, Microcystis, Spirulina, Aphanocapsa, Oscillatoria, Merismopedia, Nitzschia, Navicula, Synedra, Cosmarium and Closterium). Phytoplankton of Didwana was composed of only 9 genera including Anabaena and Nodularia. Sambhar lake, which once contained Artemia, is now totally devoid of them. On the other hand, Artemia was the most dominant zooplankter in Didwana lake at a salinity range of 15–288. Other zooplankters such as Moina, Cyclops and Brachionus flourished at lower salinity levels in Didwana lake. The seasonal quantitative and qualitative phyto- and zooplankton changes in relation to salinity are documented.     

FACTORS LIMITING EDAPHIC ALGAL BIOMASS AND PRODUCTIVITY IN A GEORGIA SALT MARSH1,2

A “planted core” system was developed to test the effect of short term (1–2 weeks) experimental manipulation of environmental parameters on edaphic microalgae under field conditions. A large number of small cores (surface area = 7 cm²) were collected, randomized and replanted in the marsh in fiddler crab exclosures with appropriate experimental treatments. Daily enrichment of the cores with NH₄⁺ resulted in significant increases in edaphic primary productivity and levels of chlorophyll a in both summer and winter seasons in the short-Spartina marsh. Enrichment with a complete nutrient solution caused no further increases. Nutrient enrichment of creekbank sediments was much less stimulatory to the resident algal assemblage. In both sites, but especially in the creekbank, the removal of fiddler crab grazers resulted in significant increases in chlorophyll a and productivity. Experimental manipulation of light intensity showed that the average light intensity reaching the sediment surface was saturating for chlorophyll production in the short-Spartina marsh. A reciprocal transplant experiment involving unfertilized cores from the short-Spartina marsh and creekbank marsh demonstrated that NH₄⁺ inputs occurring in the creekbank site rapidly alleviated nitrogen limitation of edaphic algae from short-Spartina marsh. Algae in creekbank cores incubated in the short-Spartina marsh were unable to sustain high productivity once the original standing stock of NH₄⁺ declined.