Using Plant Physiology To Improve The Water Use Efficiency Of Horticultural Crops

A study of water and hormone relations in a range of horticultural plants, conducted over a number of years, resulted in the development of a model which described the physiological mechanisms operating in these crops which control transpiration. The model relied heavily on information relating stomatal function to the ability of the roots to supply abscisic acid via the transpiration stream. Published work by other groups, which utilised split root experimental systems also lent support to this idea. Using this knowledge, we have been able to develop a commercially viable irrigation system for grapevines which has been designed to reduce vegetative vigour and improve water use efficiency. We have called the technique Partial Rootzone Drying (PRD) and it requires that the roots are simultaneously exposed to both wet and dry zones. This results in the stimulation of some of the responses normally associated with water stress such as reduced vigour and transpiration but does not result in changes in plant water status. Crop yield is relatively unaffected. Implementation of the PRD technique is simple, requiring only that irrigation systems are modified to allow alternate wetting and drying of part of the rootzone. Commercial-scale trials are currently being evaluated and further studies on the physiological mechanisms involved in modifying water use efficiency in a range of horticultural plants is continuing.