The Uptake and Transport of Chromium by Barley Seedlings (Hordeum vulgare L.)

Uptake of ⁵¹CrO^2–₄ by intact barley seedlings was linearover 24 h and was stimulated by Ca2⁺ but inhibited by SO^2–₄and other Group VI anions. Uptake increased with increasingchromate concentration, but unless the concentration was high(100 µM) less than 1 per cent of the isotope absorbedwas transported to the shoots. The results of solvent extraction,subcellular fractionation and efflux studies indicated thatmost of the isotope accumulated by the roots was present ina soluble non-particulate form in the vacuoles. The possiblereasons for the restriction in chromate transport are discussedin relation to the metabolism of the element.     

Relationships of vegetation to copper and cobalt in the copper clearings of Haut Shaba, Zaire

The vegetation of two copper clearings at Tenke Fungurumi in Zaire is described. The copper content ol the soil varied between 1000 to 130,000 ppm. Areas of highest soil copper (above 6–7000 ppni) were colonized primarily by grasses particularly Eragrostis boehmii, Sporobolus rangei and Loudetia simplex but also by other specialized cupriferous species including Becium aureoviride, Dasystachys pulchella, Anisopappus hoffmannianus and Pandiaka metallorum. Soils with 1000 to 7000 ppm copper were colonized by a community dominated by Loudetia simplex and a morphologically distinct form of Cryptosepalum maravieme. The percentage cover of Cryptosepalum was negatively correlated with soil copper. Uapaca robynsii , the most copper-tolerant woody plant, grew below 1500 ppm copper and was normally replaced by other species below approximately 1000 ppm.
The gross morphology oi Xerophyta equisetoides on three sites at Dikuluwe was investigated in relation to the soil characteristics. The growth form on Dikuluwe Hill (11,000 to 111,000 ppm copper) and a nearby non-cupriferous hill (100–200 ppm copper) were basically similar, although the morphology of the Dikuluwe Hill population was probably affected by soil copper and water stress. A distinct morphological form grew on a cupriferous (4000–5000 ppm copper) dembo site.     

Differential Protein Accumulation during Barley Grain Development

Barley grains were analysed during development for the presenceof salt-soluble proteins, hordeins and glutelins. Characteristictemporal differences between the fractions were observed withhordeins being produced relatively late during maturation. Analysisof this fraction by gel electrophoresis revealed differentialaccumulation of its component polypeptides. The C hordeins madeup a relatively higher percentage of total hordein at the earlystages, decreasing from 20% of the total at 33% final dry weightto 15% at maturity. The relative amount of the lowest molecularweight B hordein band (Bl) increased throughout developmentfrom 30% of the total at 33% final dry weight to about 45% atmaturity. Electrophoresis of the salt-soluble fraction showedthat a group of low molecular weight polypeptides appeared atthe same stage of development as did the hordeins. There wereonly relatively minor changes in the polypeptide compositionof the glutelin fraction.