Description

The nutrition of the world population in future needs an increase of plant production at locations of increasing requirements. For this, soil organic matter carries out very important contributions. Nitrogen supply for the plant is closely connected with the dynamics of the organic con- stituents in soil. Formation, transformation and degradation of soil organic matter occur mainly by biochemical reactions, which have to be known to find out the causal connections with plant production. The processes that occur during formation of the fractions of humic sub- stances in soil organic matter can be followed by labelling with radioactive or heavy isotopes. Schematically we differentiate between direct and indirect effects of constituents of soil organic matter which improve the formation of yield depending on the existing conditions. On the one side the conditions are changed in the root area, on the other the possibility exists, that sub- stances change metabolic pathways after uptake through the roots. As an example for the second case the uptake, transport and the transformation of phenolic compounds in the plant are mentioned. It is known, that those substances are formed during humification and can be isolated from soils. Some relations between chemical constitution and reactivity are more easily studied by plant cell suspension cultures.