Uptake of bromacil by isolated barley roots.

A study of bromacil uptake by excised barley (Hordeum vulgare) roots was used to evaluate this procedure as a tool to learn the uptake characteristics of toxic organic chemicals. Bromacil uptake was shown to be a passive process with an uptake rate (at 0.8 mg l(-1)) of 0.64 µg bromacil g(-1) fresh root hr(-1). A Q10 for the process was determined to be 1.5 and living roots were required for bromacil uptake. This procedure was judged to be a quick and inexpensive method to screen plant uptake of toxic chemicals.

Atmospheric benzene depletion by soil microorganisms.

Gaseous benzene was rapidly depleted in exposure chambers containing viable soils and plants. When separate components of the system were analyzed, no benzene was detected in soils, plants, or water. Soil microorganisms were shown to be responsible for metabolizing benzene, yielding CO2 as the main product. The rates were sufficiently rapid to suggest that this reaction forms a major pathway for the elimination of benzene from the environment.

Sorption of carbon tetrachloride, ethylene dibromide, and trichloroethylene on soil and clay.

The sorption of carbon tetrachloride, ethylene dibromide, and trichloroethylene in two silty clay loam soils and aluminium (Al(3+)) or calcium (Ca(2+)) saturated montmorillonite clay was studied. When the adsorbents were exposed to environmental levels of these chemicals (10 to 1000 ppb in water) the amounts of each of the chemicals sorbed were 6% or less of that available except for a 17% sorption of trichloroethylene by Al-saturated clay. In the case of the Ca-saturated clay, there was no apparent sorption of carbon tetrachloride or trichloroethylene. When soil sorption was normalized based on the soil organic carbon content (K oc) a correlation was found between the K oc, water solubility, and octanol/water partitioning coefficients of the chemicals. However, carbon tetrachloride did not behave according to with the predicted relationships.

Plant stress detection by remote measurement of fluorescence.

Chlorophyll fluorescence of mature lemon trees was measured with a Fraunhofer line discriminator (FLD). An increase in fluorescence was correlated with plant water stress as measured by stomatal resistance and twig water potential.

Cation Penetration through Isolated Leaf Cuticles.

The rates of penetration of various cations through isolated apricot Prunus armeniaca L. leaf cuticles were determined. Steady state rates were measured by using a specially constructed flow-through diffusion cell. The penetration rates of the monovalent cations in group IA followed a normal lyotropic series, i.e., CS(+) >/= Rb(+) > K(+) > Na(+) > Li(+). The divalent cations all penetrated through the cuticle more slowly than the monovalent cations. Comparison of the relative values of k (permeability coefficient) and D (diffusion coefficient) indicates that the penetration of ions through isolated cuticles took place by diffusion and was impeded by charge interactions between the solute and charge sites in the penetration pathway. Cuticular penetration rates of K(+) and H(2)O at pH above 9 were of similar magnitude. At pH 5.5 H(2)O penetration was not affected but that of K(+) was greatly reduced. From this observation and from data on cuticle titration and ion adsorption studies, we hypothesize that cuticular pores are lined with a substance (perhaps a protein) which has exposed positively charged sites.