The flow of carbon from photosynthesizing tissues of higher plants, through the roots and into the soil is one of the key processes in terrestrial ecosystems. An increased level of CO in the atmosphere will likely result in an increased input of organic carbon into the soil due to the expected increase in primary production. Whether this will lead to accumulation of greater amounts of organic carbon in soil depends on the flow of carbon through the plant into the soil and its subsequent transformation in the soil by microorganisms. In this paper the major controls of carbon translocation via roots into the soil as well as the subsequent microbial turnover of root-derived carbon are reviewed. We discuss possible consequences of an increased CO level in the atmosphere on these processes.

The mobility of different ionic forms of silver ((110m)Ag) has been studied using semiconductor radiation detectors. Silver, applied as silvernitrate (2mM), moves upward in the stems of cut carnations (Dianthus caryophyllus L.) at about 3 cm day(-1). This transport has the characteristics of a chromatographic exchange transport, but is not promoted by the addition of other cations (K(+) or Ca(2+)). The silverthiosulphate anionic complex is transported at the same speed as [(32)P]phosphate (about 2 m h(-1)); orders of magnitude faster than Ag(+). The antiethylene action of silver is preserved in this complex, as shown by a significant improvement of the longevity of carnation flowers in the presence or absence of ethephon, even after a short treatment with the silverthiosulphate complex. Analysis of the silver content of different flower parts after a silverthiosulphate treatment shows a distinct accumulation in the receptacle, possibly associated with the antiethylene action.

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