EVALUATION OF ROOT MORTALITY BY BIOCHEMICAL-ANALYSIS

The development and turnover of root systems is a dynamic process. Con tinuous initiation of new roots and the senescence of others occur sim ultaneously. Dead root skeletons persist in soil, are difficult to ide ntify by visual examination, and throw much uncertainty on root evalua tion by optical counting. In contrast, actively metabolizing constitue nts such as root protein, enzymes and coenzymes are know to decay very rapidly in senescing roots and provide therefore a potential as indic ators of root viability. From this background, root length, phosphorus (P) uptake per unit root as well as biochemical root constituents wer e studied in pot experiments with maize as dependent on plant age. Roo t dry weight and root length increased considerably with root age. In contrast to this, the P uptake rate together with protein nitrogen (N) , ATP and phosphatase activity decreased with root aging. Phosphorus u ptake rate and root protein showed similar patterns of change, suggest ing that protein N may be promising as an index of root activity.