Reciprocal effects of platinum and lead on the water household of poplar cuttings

In order to study the accumulation rates and effects of platinum as influenced by lead, experiments were performed with poplar cuttings in a growth chamber. The heavy metals were added at a final concentration of 34.8 ppb each to nutrient solutions as PtCl₄ and Pb(NO₃)₂. The variants were 1) control; 2) permanent Pt treatment for 6 weeks; 3) pretreatment with Pt plus subsequent treatment with Pb (three weeks each), and 4) heavy metal application in inverse order to variant 3. The experiments revealed that platinum accumulates in the roots of poplar cuttings to a higher degree than lead. It is translocated from the roots to other plant parts to an extremely low degree. Lead is displaced from the roots by subsequent Pt treatment. Insoluble platinum was found to be associated especially on the cell walls of the rhizodermis and exodermis of the root tips. Accumulation of platinum in the roots leads to a gradual depletion of the plants’ water supply. The disturbance of the water household causes a reduction of the transpirational surface, lowered transpiration rates and enhanced root growth. All these alterations are induced as a means of coping water stress. From the results of this experiment, the conclusion can be drawn that, under the chosen experimental conditions, platinum manifests a higher toxicity than lead in plant roots because of its higher accumulation rates.     

Promoting pro-environmental behaviour: existing evidence and policy implications

This paper describes a recent study in the UK aimed at identifying how policy makers might more effectively encourage pro-environmental behaviours amongst their target audiences. The study included analysis and synthesis of theories and models of behaviour change, a range of current policy programmes and instruments and ‘real world’ practices of individuals, households, groups and organisations.The paper highlights some important considerations for future policy within the UK and, more widely, for other countries aiming to introduce comprehensive and multi-level policy programmes to encourage pro-environmental behaviours. To this end, it emphasises the complex and non-linear nature of environmental behaviours and, thus, the importance of adopting multi-levelled and multi-instrument integrated policies across whole systems of delivery.