Keywords: Root signalling, abscisic acid, partial root zone drying, water use efficiency.

This paper highlights the important role played by roots in sensing the availability of resources in the soil. We now know that plants can ‘measure’ the water and nutrient availability around the roots as well as the mechanical impedance of the soil. This information is transferred to the shoots in the form of a chemical signal and this signalling process can allow the regulation of leaf growth and stomatal behaviour as a function of the degree of resource availability.

In the last few years it has become clear that we can exploit the plant’s endogenous signalling system and artificially regulate leaf growth and gas exchange. In some agricultural systems this will allow the regulation of leaf growth so that pruning can be minimised and water can be saved. A system of partial root zone drying is described where part of the root system is allowed to dry the soil, thereby generating root signals which have a growth regulating capacity. We describe how water and nutrient use efficiency can be significantly improved and how the system can be applied in the commercial context.

D Mingo and W J Davies, Lancaster Environment Center, Lancaster University, Bailrigg, Lancaster, UK

14 pages, 3 figures, 28 refs.