The Control of Cadmium Uptake in the Lichen Genus Peltigera

Intra- and extracellular Cd uptake in the lichen genus Peltigerawere investigated, and intracellular uptake found to displayMichaelis-Menten kinetics. Compared with values reported forZn uptake in free-living algae and fungi, Peltigera had lowaffinities for Cd and low maximum uptake rates. Intra-, andto a lesser extent extracellular uptake rates were temperaturedependent. When lichens were incubated concurrently with Cdand equimolar concentrations of a range of other cations, mostwere found to reduce both extra- and intracellular Cd uptake,implying that the Cd uptake systems had low specificities. Mg,though not a strong competitor for extracellular Cd uptake,inhibited intracellular Cd uptake to a similar extent to borderlineelements, and it is postulated that intracellular Cd uptakeoccurs by a system which normally transports Mg. Although concurrently-suppliedcations reduced Cd-induced inhibitions of photosynthesis, thereductions were not proportional to the effect of the cationson intracellular Cd uptake. This indicated that other cationsaffected the toxicity of Cd to photosynthesis by some meansin addition to reducing Cd uptake. Intracellular Cd uptake waslight-stimulated, suggesting that a close relationship existedbetween metal uptake and metabolism. The rate of intracellularCd uptake in the dark was probably not directly linked to thesupply of respirable reserves, as it was unaffected by prolongedstorage in the dark, and was not increased by adding glucose.It is hypothesized that light-stimulated Cd uptake representsactive entry into algal cells, but with uptake in the dark itis not clear which symbiont is involved, and whether energyis required. Key words: Lichen, Cadmium uptake, Temperature, Light, Cation competition     

Intracellular and Extracellular Uptake of Cadmium by the Moss Rhytidiadelphus squarrosus

Intra- and extracellular Cd uptake were investigated in themoss Rhytidiadelphus squarrosus. Intracellular Cd uptake displayedMichaelis–Menten kinetics and showed that the moss hada high uptake rate and high affinity for Cd. Extracellular Cdbinding capacity was also high. The anion used had little effecton Cd uptake to either location but both intra- and extracellularCd uptake were reduced by equimolar concentrations of Ca, Mgor Zn, although inhibition was not wholly competitive. IntracellularCd uptake was not significantly affected by the supply of energygenerating reserves but, like extracellular Cd uptake, showedaltered characteristics following growth under controlled laboratoryconditions. The results are compared with data on Cd uptakeby the lichen genus Peltigera. Rhytidiadelphus squarrosus, moss, cadmium, intra- and extracellular uptake characteristics, kinetics     

Pressure-Volume Analysis of a Range of Poikilohydric Plants Implies the Existence of Negative Turgor in Vegetative Cells

Pressure–volume (PV) isotherms were determined for a rangeof poikilohydric plants. The plants included a lichen, a filmyfern, three bryophytes and two angiosperms. Graphs of turgorpotential (