Partial characterization of the trait for enhanced K+−Na+ discrimination in the D genome of wheat

The long arm of chromosome 4D of wheat (Triticum aestivum L.) contains a gene (or genes) which influences the ability of wheat plants to discriminate between Na⁺ and K⁺. This discrimination most obviously affects transport from the roots to the shoots, in which less Na⁺ and more K⁺ accumulate in those plants which contain the long arm of chromosome 4D. Concentrations of Na⁺ and K⁺ in the roots, and Cl⁻ concentrations in the roots and shoots, are not significantly affected by this trait, but Na⁺, K⁺ and Cl⁻ contents of the grain are reduced. The trait operates over a wide range of salinities and appears to be constitutive. At the moment it is not possible to determine accurately the effect of this trait on growth or grain yield because the aneuploid lines which are available are much less vigorous and less fertile than their euploid parents.     

Milling energy requirement of the aneuploid stocks of common wheat,including alien addition lines

Summary Aneuploid stocks, which included Triticum aestivum/alien, disomic, chromosome addition lines, wheat/alien, ditelosomic, chromosome addition lines, and the available aneuploids of Chinese Spring wheat, were used to locate genes that influence milling energy requirement (ME). Genes that affected ME were found on all seven homoeologous chromosome groups. The addition of complete wheat chromosomes 1B, 1D, 2A, 2D, 5B, 6B, 7B and 7D increased ME. Positive effects were also found in specific chromosome arms: 1BS, 2DS, 5AS, 5BS and 6BL. Wheat chromosome 3B conditioned low ME and the gene(s) responsible was located on the short arm. Other negative effects were attributed to wheat chromosome arms 4BL, 4DL, 5DS and 6DS. Alien chromosome additions that conferred high ME included 2H, 5H, 6H and 7H of barley, Hordeum vulgare and 2R, 2R, 4R, 4RL, 6R, 6RL and 7RL of rye, Secale cereale. Those that conferred a low ME included 1H ^ch of H. chilense, and 6u and 7u of Aegilops umbellulata, 5R and 5RS of S. cereale and 5R ^m and 5R ^mS of S. montanum. Although the control of ME is polygenic, there is a major effect of genes located on the short arms of homoeologous group 5 chromosomes.     

The meaning of interaction parameters in two-state protein complexes

The theory of interaction parameters has thus far been based on the free-energy relationships in the formation of ternary complexes formed between a pair of ligands and a protein molecule. The concept has been formulted in terms of a thermodynamic square comprised of the free protein, the two binary complexes, and the ternary complex. However, an increasing number of proteins have been found to exist as equilibrium mixtures of two macrostates. The equilibrium constants for such two-state transitions vary quite considerably between the various binary and ternary complexes of a given protein. We show here that the interpretations of interaction parameters in such two-state systems, requiring the use of a thermodynamic cube, are much more complex than those based on the classic thermodynamic square commonly employed. We demonstrate the use of enthalpies of interaction and heat capacities of interaction to analyze the source of observed free enerigies of interaction in such systems. Specifically, we find that measured negative interaction parameters may arise simply from the inability of a system to achieve all of the positive component effects anticipated by the conventional formulation.     

Salinity tolerance of Kosteletzkya virginica. I. Shoot growth, ion and water relations

Abstract. Kosteletzkya virginica (L.) Presl., a dicotyledonous halophyte native to brackish tidal marshes, was grown on nutrient solution containing 0. 85, 170 or 255 mol m^-3 NaCl, and the effects of external salinity on shoot growth and ion content of individual leaves were studied in successive harvests. Growth was stimulated by 85 mol m^-3 NaCl and was progressively reduced at the two higher salinities. Growth suppression at high salinity resulted principally from decreased leaf production and area, not from accelerated leaf death. As is characteristic of halophytic dicots. K. virginica accumulated inorganic ions in its leaves, particularly Na⁺ and K⁺. However, the Na⁺ concentration of individual leaves did not increase with time, but remained constant or even declined, seeming to be well-coordinated with changes in water content. A striking feature of the ion composition of salinized plants was the development of a dramatic gradient in sodium content, with Na⁺ partitioned away from the most actively growing leaves. Salt-treated plants exhibited a strong potassium affinity, with foliar K⁺ levels higher in salinized plants than unsalinized plants after an initial decrease. These results suggest that selective uptake and transport, foliar compartmentation of Na⁺ and K⁺ in opposite directions along the shoot axis, and the regulation of leaf salt loads over time to prevent build-up of toxic concentrations are whole-plant features which enable K. virginica to establish favourable K⁺-Na⁺ relations under saline conditions.     

Salinity tolerance of Kosteletzkya virginica. II. Root growth, lipid content, ion and water relations

Abstract. Kosteletzkya virginica (L.) Presl., a dicot halophyte native to brackish tidal marshes, was grown on nutrient solution containing 0. 85, 170 or 255 mol m ³ NaCl, and the effects of external salinity on root growth, ion and water levels, and lipid content were examined in successive harvests. Root growth paralleled shoot growth trends, with some enhancement observed at 85 mol m ³ NaCl and a reduction noted at the higher salinities. Root Na⁺ content increased with increasing external NaCl, but remained constant with time for each treatment. K⁺ content, although lower in salt-grown plants after 14 d salinization, subsequently increased to levels comparable to unsalinized plants. A strong K⁺ affinity was reflected in the increased K⁺/Na⁺ selectivity of salt-grown plants and by their low Na⁺/K⁺ ratios. Cl levels rose in salinized plants and values were double or more those for Na⁺, indicating the possibility of a sodium-excluding mechanism in roots. Root phospholipids and sterols, principal membrane constituents, were maintained or elevated and the free sterol/phospholipids ratio increased in salinized K. virginica plants, suggesting retention of overall membrane structure and decreased permeability. This response, considered in light of root calcium maintenance and high potassium levels, suggests that salinity-induced changes in membrane lipid composition may be important in preventing K⁺ leakage from cells.     

Effect of Halide Ions on t-[35S]Butylbicyclophosphorothionate Binding

The binding of t-[35S]butylbicyclophosphorothionate [( 35S]TBPS) to a site on the GABAA receptor complex is ion dependent. This study was conducted to determine the effects of ion species and concentration on the time course, affinity, and number of sites of [35S]TBPS binding. At a concentration of 200 mM ion, the time to equilibrium for [35S]TBPS binding was shortest for I-, followed by Br- less than Cl- less than F-. A similar rank order was observed for the concentration of ion required to produce half-maximal [35S]TBPS binding. Saturation binding experiments were conducted to evaluate the effect of increasing ion concentration on the KD and Bmax of [35S]TBPS binding. The Bmax was independent of both ion species and concentration. The receptor affinity, however, increased with increasing concentration for each ion. Calculated maximal affinity values were not different between ions; however, the EC50 to produce those values was different among ions and ranked in the same order as that for time course and maximal binding data. Association and dissociation rates for [35S]TBPS binding were greater in I- than in Cl-. These data emphasize the importance of ion selection and incubation times on [35S]TBPS binding.     

On the nature of the photosynthetic energy storage monitored by photoacoustic spectroscopy

The photosynthetic energy storage yield of uncoupled thylakoid membranes was monitored by photoacoustic spectroscopy at various measuring beam intensities. The energy storage rate as evaluated by the half-saturation measuring beam intensity (i₅₀) was inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea, by heat inactivation or by artificial electron acceptors specific for photosystem I or photosystem II; and was activated by electron donors to photosystem I. The reactions involving both photosystems were all characterized by a similar maximal energy storage yield of 16±2 percent. The data could be interpreted if we assumed that the energy storage elicited by the photosystems at 35 Hz is detected at the level of the plastoquinone pool.Abbreviations PS photosystem - Tes N-Tris [hydroxymethl] methyl-2-aminoethanesulfonic acid - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DCIP 2,6-dichlorophenolindophenol - FeCN potassium ferricyanide - DCBQ 2,5-dichlorobenzoquinone - TMPD N,N,N-tetramethyl-p-phenilenediamine     

季节及人工低温对大蟾蜍肌组织ATP酶的影响研究

本文研究了大蟾蜍心肌和腓肠肌肌球蛋白钙激活ATP酶的活性。实验结果显示,大蟾蜍心肌和腓肠肌肌球蛋白钙激话ATP酶活性具有不同的季节变化规律。并且这种酶活性的季节变化不受人工低温环境因素的影响。此外,大蜍蟾心肌中ATP酶的活性始终高于腓肠肌的。上述酶活性的变化均具有一定的生理意义。     

湘南山区农业生态系统能量分析

一、引言由于农业系统的复杂性和存在较多的随机因素,对农业系统实行全面定量研究是比较困难的,仅从定性的描述和一些经济指标来判定系统的优劣及系统的特征是不理想的。而从能量观点对农业生态系统加以分析则是一个全面且能定量的方法,并且具有较强的客观性,能够反映农业生态系统最基本、最本质的关系。     

Effects of cesium on in vitro myoblast differentiation: An electron microscopic study

Summary This paper describes the microscopic evidence supporting a cesium-induced delay in the fusion of chick embryo myoblast membranes during in vitro myogenic differentiation. We have recently demonstrated that the sharp decrease in the conductivity and permittivity of the membranes of these myogenic cells at the time of fusion is delayed 30 h by the addition of cesium to the culture medium (Santini et al., Biochim. Biophys. Acta 945:56–64; 1988). We report here that this delay in fusion is substantiated by direct microscopic observation and that cesium also induces ultrastructural changes in the myoblast cells themselves. Possible mechanisms by which cesium may cause both the delay in fusion as well as the ultrastructural changes observed are discussed. This investigation was partially supported by an Italian Consiglio Nazionale delle Ricerche grant 85.00.304.02 (to P. L. I.).