Bryophytes and heavy metals: a literature review

The literature on heavy metals in bryophytes is reviewed, including mechanisms of metal uptake, retention, toxicity and tolerance. Interspecies differences in particular are discussed, including the development of extreme tolerance encountered in certain taxa. The use of bryophytes in monitoring heavy metal deposition is considered and comparisons are made with direct deposition measurements.     

Influence of Soil Moisture on Soil Solution Chemistry and Concentrations of Minerals in the Calcicoles Phleum phleoides and Veronica spicata Grown on a Limestone Soil

Veronica spicata and Phleum phleoides are calcicole plants,mainly occurring on neutral or alkaline soil. An experimentof 16 weeks duration was performed in a glasshouse with theobjective of elucidating the influence of soil moisture levelon soil solution chemistry, and biomass concentrations and uptakeof mineral nutrients by the plants. Seven levels of moisture,corresponding to 35–85% of the water holding capacity(WHC) of the soil, were tested. Soil solution HCO₃, P and Mnconcentrations, and pH, increased, whereas Ca, Mg and Zn concentrationsdecreased, with increasing soil moisture. Concentrations ofK were highest at 50–70% WHC. Concentrations and amountsof P, Zn and Mn in the two species were usually related to soilsolution concentrations; these are elements with low solubilityand availability in calcareous soils. Concentrations of nutrientsin biomass were more influenced by soil moisture in V. spicatathan inP. phleoides . This indicates that P. phleoides is morecapable of controlling its uptake of mineral nutrients, whereasV. spicata is sensitive to variations in soil moisture. It isconcluded that variation in soil moisture regime may greatlyinfluence concentrations of mineral nutrients in calcareoussoil solutions and their uptake by plants. Species able to utilizethese solubility fluctuations may have an advantage in competitionfor nutrients. Variation in soil moisture content might evenbe a prerequisite for adequate acquisition of mineral nutrientsand growth of plants on limestone soils, thereby influencingthe field distribution of native plants among habitats. Copyright1999 Annals of Botany Company Calcareous, calcicole, concentration, mineral, moisture, nutrient, Phleum phleoides, soil, soil solution, uptake, Veronica spicata, water.     

Differences in Iron Nutrition Strategies of Two Calcifuges,Carex piluliferaL. andVeronica officinalisL.

Veronica officinalisandCarex pilulifera, widespread calcifugeplants in Europe, were cultivated in acid and calcareous soilsto study differences in Fe aquisition strategies indicated inprevious studies. The experiments were performed in a computer-controlledglasshouse at a soil solution moisture content of 50–60%water holding capacity; additional light was supplied at 70W m^-2if ambient light was <100 W m^-2between 0600 and 1800h.Both species developed chlorosis when grown in the calcareoussoil.C. piluliferaproved unable to translocate sufficient amountsof Fe to the leaves when cultivated in calcareous soil, butmuch Fe accumulated in, and especially as a precipitate on thesurface of roots. In contrast,V. officinalistended to increaseFe taken up into the leaves of plants grown on calcareous soil,but a much greater proportion of the leaf tissue Fe was accumulatedas less active forms not extracted by Fe complexing agents,e.g. 1,10-phenanthroline, than was the case in acid-soil grownplants. Considerably less Fe was accumulated in the root biomassofV. officinaliscompared toC. pilulifera.It is concluded thatchlorosis inC. piluliferais related to insufficient Fe uptakein the leaves, whereas leaf immobilization of Fe in physiologicallyless active forms is the problem inV. officinalis. Iron; chlorosis; calcifuge; iron immobilization; leaf tissue; fractionation; Carex pilulifera; Veronica officinalis