Water relations ofZygophyllum hamiense, Heliotropium kotschyiandPanicum turgidumand their response to rangeland management techniques in Abu Dhabi

The diurnal water relations of two weeds of irrigated rangeland in Abu Dhabi and one important forage plant were investigated to determine reasons for their distribution and response to irrigation and topsoiling.Zygophyllum hamiense, a weed of sprinkle irrigated rangeland, was found to have a relatively low water potential which together with its succulent habit was interpreted to indicate its tapping of brackish and/or saline ground-water reserves. This also accounted for its distribution in depressions in the landscape, on disturbed areas such as sand sheets with stores of water, and irrigated areas.Heliotropium kotschyidominated drip irrigated areas mainly through its rhizome growth habit. It showed stomatal control of water loss during the course of the day but still had to shed branches to survive the dry season without irrigation.Panicum turgidumshowed no control of water loss and had the highest diurnal variation in water potential. The lack of water-loss control was reflected in its deciduous habit during the dry part of the year. Recommendations were made for irrigation schemes in Abu Dhabi to promote the growth ofP. turgidumrather thanZ. hamienseorH. kotschyi.