Properties of a new strain of tobacco streak virus from Clematis vitalba (Ranunculaceae)

A distinct strain of tobacco streak virus (TS V/Cle), isolated in Yugoslavia from wild Clematis vitalba showing chlorotic spots or yellow netting of the leaves and from many symptomless shrubs, is described. TSV/Cle was seed transmitted in C. vitalba (70%), and in the experimental hosts Chenopodium quinoa (80%), Nicotiana benthamiana and N. megalosiphon. It was also detected in the pollen of infected C. quinoa. Purified virus preparations mostly contained quasi-spherical particles measuring 24–26 × 28, 26–28 × 28–30 and 28–31 × 32–36 mn, and sedimented in sucrose density gradient and analytical centrifugation as three components with sedimentation coefficients of 76S, 87S and 98S. The virus contained a single polypeptide species of mol. wt of c. 25 000. Unfractionated TSV/Cle preparations contained four RNA species with mol. wts, estimated by gel electrophoresis in agarose, of 1.1 × 10⁶, 0.9 × 10⁶, 0.7 × 10⁶ and 0.3 × 10⁶. In comparative experiments, TSV/Cle differed from four reference strains of TSV (TSV/B, TSV/HF, TSV/RN, and TSV/Ro) in host range and in symptoms induced in some common hosts. In agar gel double diffusion tests it was more closely related to TSV/B and TSV/M (SDI = 5) than to TSV/HF (SDI = 7), TSV/RN (SDI = 7) or TSV/Ro (SDI = 5–8). Immunoelectrophoresis experiments clearly distinguished TSV/Cle from the reference strains. TSV/Cle strain was detected in C. vitalba plants from distant and climatically different regions in Yugoslavia.     

Effect of high external NaCl concentrations on ion transport within the shoot of Lupinus albus. I. Ions in xylem sap

Abstract. Xylem sap was collected from individual leaves of intact transpiring lupin plants exposed to increasing concentrations of NaCl by applying pneumatic pressure to the roots. Concentrations of Na⁺ and Cl⁻ in the xylem sap increased linearly with increases in the external NaCl concentration, averaging about 10% of the external concentration. Concentrations of K⁺ and NO₃⁻, the other major inorganic ions in the sap, were constant at about 2.5 and 1.5 mol m⁻³, respectively. There was no preferential direction of Na ⁺ or Cl⁻ to either young or old leaves: leaves of all ages received xylem sap having similar concentrations of Na⁺ and Cl⁻, and transpiration rates (per unit leaf area) were also similar for all leaves. Plants exposed to 120–160 mol m⁻³ NaCl rapidly developed injury of oldest leaves; when this occurred, the Na⁺ concentration in the leaflet midrib sap had increased to about 40 mol m⁻³ and the total solute concentration to 130 osmol m⁻³. This suggests that uptake of salts from the transpiration stream had fallen behind the rate of delivery to the leaf and that salts were building up in the apoplast.     

Na+, K+ and Cl- in Xylem Sap Flowing to Shoots of NaCl-Treated Barley

Munns, R. 1985. Na⁺, K⁺ and Cl^– in xylem sap flowing toshoots of NaCl-treated barley.—J. exp. Bot. 36: 1032–1042. Na⁺, Cl^– and K⁺ concentrations were measured in xylemsap obtained by applying pressure to the roots of decapitatedbarley plants grown at external [NaCl] of 0, 25, 50, 100, 150and 200 mol m^–3. For any given NaCl treatment, ion concentrationsin the xylem sap were hyperbolically related to the flux ofwater. Ion concentrations in sap collected at very low volumefluxes (without applied pressure) were 5–10 times higherthan in sap collected at moderate fluxes (under pressure). Fora given moderate volume flux, Na+ concentration in the xylemsap, [Na⁺]_x, was only 4.0 mol m^–3 at external [NaCl] of25–150 mol m^–3, and increased to 7.0 mol m^–3at 200 mol m^–3. [Cl-]x showed a similar pattern. Thisshows there would be little difference in the rate of uptaketo the shoot of plants at 25–150 mol m^–3 externalNaCl and indicates little change even at 200 mol m^-3 NaCl becausetranspiration rates would be much lower. Thus the reduced growthof the shoot of plants at high NaCl concentrations is not dueto higher uptake rates of Na⁺ or Cl^–. The fluxes of Na⁺, Cl^– and K^– increased non-linearlywith increasing volume flux indicating little movement of saltin the apoplast. The flux of K⁺ increased even when [K⁺]_x wasgreater than external [K⁺], indicating that membrane transportprocesses modify the K⁺ concentration in the transpiration streamas it flows through the root system. Key words: -Xylem sap, Na⁺, K⁺, Cl^– fluxes, salinity, barley     

Turgor Pressure, Volumetric Elastic Modulus, Osmotic Volume and Ultrastructure of Chlorella emersonii Grown at High and Low External NaCl

Chlorella emersonii (211/11n) was grown at external NaCl concentrationsranging between 1.0 and 335 mM (0.08–1.64 MPa). Previousstudies showed that there was no significant change in the internalconcentrations of Na⁺ or Cl^– over this range, the concentrationsremaining below 35 mM. Relative growth rates of C. emersoniiwere 30–45% lower in 335 mM NaCl than in 1.0 mM NaCl.Turgor pressure varied with the osmotic pressure of the growthmedium. Plots of cell volume versus (external osmotic pressure)^–1indicated that cells grown in 1.0 mM NaCl (0.08 MPa) had turgorpressures ranging from 0.5 to 0.8 MPa, while cells in 335 mMNaCl (1.64 MPa) had turgor pressures of 0.0–0.14 MPa.Estimates of turgor pressure derived from the osmotic pressureof cell sap had a mean value of 0.6 MPa for cells in 1.0 mMNaCl, and 0.3 MPa for cells in 335 mM NaCl. The volumetric elasticmodulus () depended on the osmotic pressure of the growth medium: was 8.5 ± 1.7 MPa for cells grown in 1.0 mM NaCl, and0.9 ± 0.6 for cells in 335 mM NaCl. was measured bychanging turgor pressures over the range 0.0–0.5 MPa,and was found to be independent of turgor. Electron micrographsshowed that the walls of cells grown in 335 mM NaCl were 70%thicker than those grown in 1.0 mM NaCl. Other changes in cellularstructure were small, however, the area occupied by vacuolesincreased from 7% in cells grown in 1.0 mM NaCl to 14% in cellsin 335 mM. The percent osmotic volume of cells grown in 1.0–335mM NaCl (61 ± 17%, v/v) was similar to the percent watercontent (59 ± 13%, w/w). Key words: Chlorella emersonii, Sodium chloride, Osmotic volume, Turgor, Volumetric-elastic-modulus     

Effects of accumulation of 3-O-methylglucose on levels of endogenous osmotic solutes in Chlorella emersonii

Abstract. Regulation of the concentration of osmotic solutes was studied in Chlorella emersonii grown at external osmotic pressures (II) ranging between 0.08 and 1.64MPa. NaCl was used as osmoticum. The total solute content of the cells was manipulated by applying 2 mol m⁻³ 3- O -methylglucose (MG), which was not metabolized, and accumulated at concentrations ranging between 60 and 230 mol m⁻³ within 4 h after its addition to the medium. Methylglucose uptake resulted in decreases in concentrations of proline and sucrose, the two solutes mainly responsible for osmotic adaptation of C. emersonii to high external II. The responses were consistent with the hypothesis that proline and sucrose concentrations are controlled by a system of osmotic regulation, with turgor and/or volume as a primary signal. Short-term experiments showed that even very small increases in turgor and/or volume, due to accumulation of methylglucose, resulted in large decreases in proline and sucrose. Over the first 30-60 min the total solute concentration in the cells increased by at most 15 osmol m⁻³ which would represent an increase in turgor pressure of at most 0.04 M Pa. Yet, the decreases in proline and sucrose were as fast as those in cells exposed to a sudden decrease of 0.25 MPa in external II, when the turgor pressure would have increased by at least 0.15 MPa. High concentrations of methylglucose in cells grown at high II did not affect the rapid synthesis of proline and sucrose which started when the cells were transferred to yet higher II. Thus, methylglucose had no direct effects on proline and sucrose metabolism, and it has been assumed that it acted solely as an inert osmotic solute within the cell.     

CURRICULUM GUIDE FOR RESEARCH ETHICS WORKSHOPS FOR COUNTRIES IN THE MIDDLE EAST

To help ensure the ethical conduct of research, many have recommended educational efforts in research ethics to investigators and members of research ethics committees (RECs). One type of education activity involves multi‐day workshops in research ethics. To be effective, such workshops should contain the appropriate content and teaching techniques geared towards the learning styles of the targeted audiences. To ensure consistency in content and quality, we describe the development of a curriculum guide, core competencies and associated learning objectives and activities to help educators organize research ethics workshops in their respective institutions. The curriculum guide is divided into modular units to enable planners to develop workshops of different lengths and choose content materials that match the needs, abilities, and prior experiences of the target audiences. The content material in the curriculum guide is relevant for audiences in the Middle East, because individuals from the Middle East who participated in a Certificate Program in research ethics selected and developed the training materials (e.g., articles, powerpoint slides, case studies, protocols). Also, many of the activities incorporate active‐learning methods, consisting of group work activities analyzing case studies and reviewing protocols. The development of such a workshop training curriculum guide represents a sustainable educational resource to enhance research ethics capacity in the Middle East.     

Microsatellite markers for the palaeotropic pioneer tree genus Macaranga (Euphorbiaceae) and their cross‐species transferability

We developed primer sequences for five polymorphic microsatellite loci in the tropical ant‐plant genus Macaranga (Euphorbiaceae). Population genetic parameters were determined on the basis of 30 individuals from each of two Macaranga species in Borneo. Allele numbers per locus ranged from three to 13. Expected and observed heterozygosities ranged from 0.160 to 0.850 and from 0.130 to 0.700, respectively. Four of the five primer pairs cross‐amplify polymorphic PCR products in a wide range of Macaranga species.     

Nucleotide diversity and phylogenetic relationships among <Emphasis Type="Italic">Gladiolus</Emphasis> cultivars and related taxa of family Iridaceae

The plastid genome regions of two intergenic spacers, psbA–trnH and trnL–trnF, were sequenced to study the nucleotide diversity and phylogenetic relationships among Gladiolus cultivars. Nucleotide diversity of psbA–trnH region was higher than trnL–trnF region of chloroplast. We employed Bayesian, maximum parsimony (MP) and neighbour-joining (NJ) approaches for phylogenetic analysis of Gladiolus and related taxa using combined datasets from chloroplast genome. The psbA–trnH and trnL–trnF intergenic spacers of Gladiolus and related taxa-like Babiana, Chasmanthe, Crocus, Iris, Moraea, Sisyrinchium, Sparaxis and two out group species (Hymenocallis littoralis and Asphodeline lutea) were used in the present investigation. Results showed that subfamily Iridoideae have sister lineage with subfamily Ixioideae and Crocoideae. H. littoralis and A. lutea were separately attached at the base of tree as the diverging Iridaceae relative’s lineage. Present study revealed that psbA–trnH region are useful in addressing questions of phylogenetic relationships among the Gladiolus cultivars, as these intergenic spacers are more variable and have more phylogenetically informative sites than the trnL–trnF spacer, and therefore, are suitable for phylogenetic comparison on a lower taxonomic level. Gladiolus cultivars are extensively used as an ornamental crop and showed high potential in floriculture trade. Gladiolus cultivation still needs to generate new cultivars with stable phenotypes. Moreover, one of the most popular methods for generating new cultivars is hybridization. Hence, information on phylogenetic relationships among cultivars could be useful for hybridization programmes for further improvement of the crop.