PHOSPHORUS AVAILABILITY AND CORTICAL SENESCENCE IN CEREAL ROOTS

Genetically programmed senescence of the cortex occurs in cereal roots. Its evolutionary origin is obscure. One possibility is that it might be a consequence of constraints on the amount of phosphorus available for root growth imposed by the relatively low potential rate of phosphorus uptake from the soil. If phosphorus is recycled from old cortical cells, the resulting cost of root growth is calculated to be less than the gain of phosphorus by the root, supporting this possibility. © 1990 Academic Press Limited.