Abstract: Diurnal changes of water potential in apricots were mainly controlled by 'changes of saturation vapour pressure deficit (VPD) (or relative humidity), air temperature and light intensity in a day. The daily minimum value of leaf water potential was determined by light intensity. During the course of a day, leaf water potential decreased gradually with increasing VPD and air temperature. Daily minimum value of leaf water potential was reached at a VPD of 4–7 mbars early in the growing season and 12–15 mbars late in the growing season, and at an air temperature of about 19℃ in the whole growing season. Thereafter leaf water potential stayed constantly until air temperature and VPD reached daily maximum value, at the same time, the minimum value of leaf water potential at the different parts of a shoot and a canopy showed no difference, if other conditions were the same. Plastic film cover and irrigation were able to increase soil water potential, but have few effects on leaf water potential.

Key words: Prunus armeniaca L., Leaf water potential, Soil water potential, Saturation vapour pressure deficit, Meteorological factors