Vegetation of a coastal sand dune system in southern New Zealand

The introduction of vigorous exotic species has destroyed much of the native sand dune vegetation along the coasts of South Island, New Zealand. However, some dunes built by the native cyperad Desmoschoenus spiralis still remain in the southwest. The dunes at Cole Creek, on the West coast of South Island, were chosen as a relatively pristine study area. 15 transects were laid through semi-fixed dunes into dwarf forest. Environmental measurements were taken at regular intervals through the dunes: pH, soil moisture, organic matter, conductivity, nutrient status and elevation. Classification and ordination of these data demonstrated that two major environmental areas were present - open dune and dwarf forest - with an abrupt ecotone between them. Vegetation analyses revealed a loosely-banded pattern, parallel to the sea. Vegetation types with few but constant species such as Desmoschoenus spiralis and Calystegia soldanella, predominated in the open dune. Forest species were rarely found seaward of the dune/forest boundary, though there was evidence the Spatial Mass Effect was operating. Multiple regression and canonical correlation of the vegetation and environmental factors showed that the main factors affecting vegetation patterns were the environmental complex related to distance from the sea, elevation above mean tide, soil alkalinity and moisture.     

The inheritance of salt exclusion in woody perennial fruit species

Citrus and grapevines are salt-sensitive perennial crops. Damage caused by salinity is due mostly to accumulation of excessive concentrations of salt (Na- and Cl ions) in shoot tissues. In both crops, however, some rootstock varieties can restrict the accumulation of salt in scion leaves and stems. Salt-excluding rootstocks, however, are often deficient with regard to other desirable characteristics and as such their use is limited. As a consequence, we have conducted a range of crosses within both crops to select new salt-excluding hybrids which may have potential as new rootstocks and also to investigate the inheritance of salt exclusion in these woody perennials.In citrus, both Cl-ion and Na-ion exclusion has been observed as a continuous character and progenies segregate widely for their ability to restrict the accumulation of these ions in shoot tissues. The ability to exclude Cl ions appears to be independent of the ability to exclude Na ions. Thus a good Cl-ion excluder is not necessarily a good Na-ion excluder and vice versa. It has been possible, however, to select new salt-excluding citrus hybrids which perform as well as and sometimes better than parent varieties when grafted with a common scion and grown in artificially salinised field plots.In grapevines, the research has concentrated on the ability for Cl-ion exclusion and depending on the Cl-ion-excluding parent chosen this is inherited as either a polygenic or monogenic trait. In crosses between Vitis champini (Cl-ion excluder) and Vitis vinifera (Cl-ion accumulator), the ability to restrict Cl-ion accumulation in shoot tissues segregates widely with some offspring transgressing the performance of either parent. In crosses and backcrosses involving V. berlandieri and V. vinifera, however, hybrids segregate as either Cl-ion excluders or accumulators suggesting the effect of a major dominant gene for Cl-ion exclusion from V. berlandieri. This was evident from both field and glasshouse experiments although possible modifying genes from V. vinifera may affect the expression of this gene under glasshouse conditions in some crosses.     

Tetracyano-2,2-bipyridineiron(iii), an improved electron acceptor for the spectrophotometric assay of beta-oxidation and of succinate dehydrogenase in intact mitochondria.

A recently described direct reading assay for beta-oxidation and for succinate oxidation in intact mitochondria using [Fe(CN)6]3- as final electron acceptor [Osmundsen & Bremer (1977) Biochem. J. 164. 621--633] has been improved by using instead tetracyano-2,2-bipyridineiron(III) [Fe(CN)4(bpy)]-, which gives a 2.6 times greater absorbance change on reduction. Some physical and kinetic properties of [Fe(CN)4(bpy)]- are described. The use of exogenous cytochrome c(III) as electron acceptor was also tested; this gives the largest absorbance change, although the absolute rate of reaction is only approx. one-third of that using [Fe(CN)6]3- or [Fe(CN)4(bpy)]-.     

Neutral complexes as oxidants for the reduced form of parsley (Petroselinum crispum) [2Fe--2S] ferredoxin. Evidence for partial blocking by redox-inactive Cr(III) complexes.

The 1 : 1 reactions of three neutral Co(III) oxidants, Co(acac)3, Co(NH3)3(NO2)3 and Co(acac)2(NH3)(NO2), with reduced parsley (Petroselinum crispum) [2Fe--2S] ferredoxin (which carries a substantial negative charge), have been studied at 25 degrees C, pH 8.0 (Tris/HCl), I0.10 (NaCl). Whereas it has previously been demonstrated that with Co(NH3)6+ as oxidant the reaction if completely blocked by redox-inactive Cr(NH3)63+, the neutral oxidants are only partially blocked by this same complex. The effects of three Cr(III) complexes, Cr(NH3)63+%, Cr(en)33+ and (en)2Cr . mu(OH,O2CCH3) . CR(en)24+ have been investigated. Kinetic data for the response of 3+, neutral, as well as 1--oxidants to the presence of 3+ (and 4+) Cr(III) complexes can now be rationalized in terms of a single functional site on the protein for electron transfer. Electrostatics have a significant influence on association at this site.     

Cerebral Glutamic Acid Decarboxylase Activity and γ-Aminobutyric Acid Concentrations in Mice Susceptible or Resistant to Audiogenic Seizures

Abstract: DBA/2 mice between 21 and 28 days of age are highly susceptible to sound-induced seizures. Drug studies suggest a possible deficit of γ-Aminobutyric acid (GABA)-mediated neurotransmission may be involved. We have measured the whole brain GABA concentration and glutamic acid decar-boxylase activity in DBA/2 mice at various ages before, during, and after the period of maximal susceptibility to audiogenic seizures. Corresponding determinations were carried out on age-matched TO mice, a strain much less susceptible to audiogenic seizures than DBA/2 mice at all ages. No significant differences in GABA concentration or glutamic acid decarboxylase activity were found between strains at any age. The susceptibility of DBA/2 mice to audiogenic seizures does not result from a gross inability to synthesise or store GABA.     

Meiosis in the aquatic fungusCatenaria allomycis

Summary Catenaria allomycis Couch (Blastocladiales) is an endobiotic fungal parasite primarily of species of the genusAllomyces. The life cycle ofC. allomycis contains both sexual and asexual phases. Synaptonemal complexes have been found in young developing resistant sporangia (RS) suggesting that meiosis occurs within the thick walled RS prior to syngamy. Ultrastructural evidence suggests that meiosis proceeds through pachytene in the developing RS and is arrested in diplotene of prophase I until the sporangia are induced to germinate at which time the meiotic process is completed. Quantitative nuclear counts in developing RS support the ultrastructural observations. Meiotic nuclei are characterized by polar fenestrae in the nuclear envelope and intranuclear plaque-like microtubule organizing centers (MTOC).Portion of a Ph.D. dissertation submitted by the senior author to the Graduate School, University of Georgia.     

Nuclear magnetic resonance determination of intramolecular distances in bovine pancreatic trypsin inhibitor using nitrotyrosine chelation of lanthanides.

Nitration of tyrosine has been investigated as a means for chemically introducing lanthanide chelating sites at known positions in proteins. The low-field portions of the 250-MHZ and 270-MHZ 1H nuclear magnetic resonance spectra of native and chemically modified bovine pancreatic trypsin inhibitor have been studied in the presence of lanthanide ions. Comparisons of spectral changes observed with native, mononitro (tryosine 10) and dinitro (tyrosines 10 and 21) derivatives enable these changes to be separately attributed to metal bound at nitrotyrosine 21, nitrotyrosine 10, or the set of five carboxyl groups. The pH dependence of Pr(III) and Eu(III) induced chemical shifts yields stability constants of 50 and 159 M-1 for the association between lanthanides and nitrotyrosines 10 and 21, respectively. Correlation times for the interactions with Gd(III) bound to specific nitrotyrosines are estimated from the induced line broadening of resonances of the nitrotyrosine ring protons. These stability constants and correlation times are used to determine the distances from the different metal binding sites to buried backbone NH protons having resolved resonances. Comparisons with distances in the x-ray crystal structure give assignments of the NH resonances to a small set of buried backbone NH's.     

Complete tyrosine assignments in the high field 1H nuclear magnetic resonance spectrum of the bovine pancreatic trypsin inhibitor.

The low-field portions of the 250-MHz 1H nuclear magnetic resonance (NMR) specra of native and chemically modified bovine basic pancreatic trypsin inhibitor (BPTI) have been studied as a function of pH over the range pH 5-13. Resonances associated with the 16 protons of the aromatic rings of the four BPTI tyrosines have been located and assigned to specific tyrosyl residues. Titrations of pH yielded pK's for tyrosines-10, -21, -23, and -35 of 10.4, 11.0, 11.7, and 11.1, respectively. The resonances associated with the nitrotyrosine-10 protons of mononitrated BPTI and the nitrotyrosine-10 and -21 protons of dinitrated BPTI have been similarly located, assigned and titrated yielding pK's for nitrotyrosine-10 and -21 of 6.6 and 6.4, respectively. The high-field NMR spectrum indicates that the aromatic ring of tyrosine-35 rotates less than 160 times per second at 25 degrees for pH's in the range 5-9.