Variability in vibration perception threshold among sites: a potential source of error in biothesiometry

Vibration perception threshold was measured with a biothesiometer by a single observer at both medial malleoli and both big toes in 110 diabetic patients aged 15-65 selected at random and in 64 non-diabetic subjects aged 20-65. The vibration perception threshold showed appreciable individual variation both between contralateral sites and between ipsilateral sites, differing by at least 30% between the big toes in 26 (24%) of the diabetic patients and 16 (25%) of the non-diabetic group. Variability between sites was significantly greater in the diabetics than the normal subjects. The vibration perception threshold exceeded published normal values at one or more sites in 22 of the diabetic patients but at all four sites in only four.The wide variability in vibration perception threshold among sites may be due to the tissue characteristics locally and, in diabetic patients, possibly to asymmetric neuropathy. Biothesiometer readings at single or unilateral sites may be unrepresentative or misleading.     

The Production of Leaves and Stolon Branches on Established White Clover Cuttings in Relation to Temperature and Soil Moisture in the Field

Successive sets of cuttings of three white clover genotypeswere raised in a 15 °C growth room and transferred to thefield at 14 d intervals over the course of a year. Rates ofleaf appearance (leaves per stolon growing point per unit time)were found to be closely correlated with 10 cm soil temperatures.Petiole lengths, and weights of the lamina+petiole increasedin May and decreased towards the end of August, but also exhibiteda marked response to a mid-season water deficit. In the conditionsof the experiment (i.e. in the absence of competition from neighbouringplants) the vast majority of axillary buds developed into visiblebranches at all times of the year. There was, however, an increasein the nodal age at which bud development was first observedin winter. Deferred bud development was also observed, particularlyin one genotype, during periods characterized by dry soil surfaceconditions. The results are discussed in relation to observedpatterns of stolon branching in sward conditions. White clover, Trifolium repens, axillary bud development, branching, growing points, leaf appearance rate, petiole length, soil moisture, soil temperature     

The effect of powdery mildew (Erysiphe graminis f.sp. avenae) on yield, yield components and grain quality of spring oats

Yield components and grain quality were investigated on eight cultivars of spring oats with known differences in adult plant resistance to mildew and with different fungicide treatments. Losses in grain yield caused by mildew could be accounted for mainly by reductions in numbers of fertile panicles and thousand grain weights. The proportion of grain yield to total biomass, (harvest index) was also reduced. There were no effects of treatment on the concentration of fatty acids in the grain, the proportions of the component fatty acids, the percentage content of grain protein or the specific weights. However, correlation analysis of the data revealed that percentage protein contents and specific weights were negatively correlated with levels of mildew. There were significant genetic differences between cultivars in all of the yield and quality characteristics but no fungicide treatment/cultivar interactions.     

The Seasonal Pattern of Growth and Production of a Temperate C4 Species, Cyperus longus

Growth and production of the temperate C₄ species Cyperus longusL. was measured throughout a growing season in an establishedplot in Eastern Ireland. The maximum standing live biomass reachedwas 2·5 kg m^–2. Estimates of unit leaf rate (ULR)and leaf area index (LAI) were made. The product of these quantitiesgave the crop growth rate (CGR) each week. C. longus was foundto maintain high values of LAI throughout the summer, with amaximum value of about 13 in early August. CGR reached a peakin early July. The optimum LAI was 11·6. Temperaturesat five levels in the plant canopy, and the amount of solarradiation intercepted by the canopy were measured continuouslyduring the summer. The mean daily rate of leaf extension waspositively correlated with the mean daily air temperature abovethe canopy but the temperature coefficient of the process waslow compared with other temperate species. The percentage ofsolar radiation intercepted by the canopy increased rapidlyin early summer, and canopy closure had occurred by mid-June.Rates of net photosynthesis were measured on young and old leafmaterial in situ at the time of peak LAI. In young leaves themaximum rates of net photosynthesis were higher than those publishedfor a range of temperate C₃ species, but similar to those foundin another temperate C₄ species, Spartina townsendii. Key words: C₄ photosynthesis, leaf growth, productivity     

Salt Tolerance in the Triticeae: Salinity-induced Changes in the Leaf Solute Composition of Some Perennial Triticeae

Changes in the leaf solute composition of a number of perennialTriticeae in response to salinity are described. There was variationboth within and between species in the extent of Na and Cl accumulationin the leaves. In almost all cases leaf nitrate concentrationsdecreased substantially and orthophosphate concentrations increasedin response to salinity. There was no overall decrease in arange of soluble nitrogen-containing compounds nor in totalnitrogen. In Thinopyrum scirpeum there was an inverse relationshipbetween proline and glycinebetaine contents of different tissues,with proline levels higher in older leaves. Concentrations ofboth compounds were higher in salt-stressed plants. Key words: Triticeae, salinity, leaf solute composition     

Biological and biochemical properties of an isolate of cherry rasp leaf virus from red raspberry

A mechanically transmissible virus obtained from symptomless plants of a red raspberry selection imported into Scotland from Quebec, Canada was indistinguishable serologically from a cherry isolate of cherry rasp leaf virus (CRLV). The raspberry isolate, CRLV-R, was graft transmitted to several virus indicator species and cultivars of Rubus without inducing noticeable symptoms. In Chenopodium quinoa sap, CRLV-R lost infectivity after dilution to 10^-5 or heating for 10 min at 60°C but was infective after 16 days (the longest period tested) at 18°, 4° or - 15°C. The virus particles are isometric, c. 28 nm in diameter, and were purified with difficulty from infected C. murale and C. quinoa plants. The particles comprise two nucleoprotein components with sedimentation coefficients of 89 and 115 S and are prone to aggregate during purification. When centrifuged to equilibrium in CS₂SO₄ solution, purified virus preparations formed two major components with p= 1·28 and 1·36 g/cm³. Virus particles contained two RNA species which, when denatured in glyoxal and electrophoresed in agarose gels, had estimated mol. wt of 2·56 × 10⁶ (RNA-1) and 1·26 × 10⁶ (RNA–2). Infectivity of CRLV-R RNA was abolished by treatment with proteinase K, suggesting that the RNA is linked to protein necessary for infectivity; RNA molecules contained polyadenylate. In reticulocyte lysates, CRLV-R RNA stimulated the incorporation of ³H-leucine, mainly into two polypeptides of estimated mol. wt 200 000 and 102 000. When electrophoresed in polyacrylamide gels, protein obtained from CRLV-R particles purified by centrifugation to equilibrium in Cs₂SO₄ separated into three bands with estimated mol. wt 26 000 , 23 000 and 21 000.     

Salt Tolerance in the Triticeae: Leymus sabulosus

Elymus dahuhcus, Leymus giganteus, L. angustus, L. sabulosusand, to a lesser extent, L. triticoides, were found to tolerate200 mol m^–3 NaCl in solution culture. Elymus dahuricusdiffered from the Leymus species in its ion-uptake characteristics,showing a greater uptake of Cl and Na and a greater loss ofK from the shoots. In a more detailed experiment on Leymus sabulosusit was found that transpiration rates altered rapidly in responseto changes in external salinity whereas the accumulation ofNa and Cl in the leaves exhibited a lag of several days. Insalt stressed L. sabulosus Cl partially replaced the high levelsof nitrate found in the leaves of control plants. Glycinebetainelevels increased in the leaves from 8.0 mol m^–3 plantsap in the controls to 28 mol m^–3 plant sap at 250 molm^–3 NaCl. Key words: Salt stress, Transpiration, Solute accumulation, Leymus     

Conductimetric assessment of the biomass content in suspensions of immobilised (gel-entrapped) microorganisms

Summary The problem of obtaining a rapid estimate of the microbial content of an immobilised cell suspension is addressed. The low-frequency conductivity of free-living cell suspensions of Clostridium pasteurianum is lower than that of the medium in which they are suspended, by an amount conforming to the Bruggeman relation. The conductivity of the cell wall makes a negligible contribution to the measured conductivity under the conditions used. Calcium alginate beads (lacking microbial cells) lower the conductivity of a solution with which they have been equilibrated by an extent which is a function of the concentration of alginate gel used in forming the beads. When this is taken into account, the ratio of the conductivity of a suspension of gel-immobilised cells to that of the suspending medium can be used to give a rapid and convenient assessment of the amount of microbial biomass present.     

Insects on isolated colonies of common rock-rose Helianthemum chamaecistus

ABSTRACT.

• 1 A study was made of the insect species present on twenty-eight colonies of H.chamaecistus Mill, in 1978 ranging in size (cover) from 0.4 m² to about 6500 m² and separated from nearest large neighbours by distances up to 6.5 km. Twenty-three insect species were collected of which nine or ten were more or less monophagous.
• 2 There was a clear relationship between species richness and size of host colony. Sites with less than 30 m² of rock-rose, about 67% of those in the study area, were likely to have less than half of the monophagous species. Distance to neighbouring colonies did not contribute significantly to species richness.
• 3 The consistency of results from year to year was examined at five sites re-sampled in 1979. The 1978 data were also used to compare‘expected’and observed faunas at five new sites sampled in 1979 based upon the species-area relationship and the relative frequency of species at known sites.
• 4 Insect dispersal was examined using a suction trap placed near the largest rock-rose site. Colonization of new sites was studied by experimental outplanting of pot-grown plants.
• 5 These direct observations, and the monitoring of fourteen sites for 5 years, suggested that colonization and interchange of faunas were rare events. The experimental introduction of one to five species at four sites showed in several cases that the sites were suitable for the species, and that introduction could significantly enhance a site's complement.