Phosphorus nutrition of woody plants: many questions - few answers.

Phosphorus (P) acquisition, cycling and use efficiency has been investigated intensively with herbaceous plants. It is known that local as well as systemic signalling contributes to the control of P acquisition. Woody plants are long-lived organisms that adapt their life cycle to the changing environment during their annual growth cycle. Little is known about P acquisition and P cycling in perennial plants, especially regarding storage and mobilisation, its control by systemic and environmental factors, and its interaction with the largely closed ecosystem-level P cycle. The present report presents a view on open questions on plant internal P cycling in woody plants.