Diurnal and seasonal variations of CWSI and non-water-stressed baseline with nectarine trees.

摘要

The work described was part of the programme 'Innovative biological indicators to improve the efficiency of water and nitrogen use and the fruit quality in tree crops project', a partnership between ISA and INRA. Field studies were conducted in Portugal (south bank of Tagus river, 40 km east of Lisbon) in July 1998, on different irrigated plots of nectarine (cv. Sylver King) trees. Treatments were a fully irrigated (unstressed plot) and a plot that was not irrigated for some days (stressed plot). The aim of this work was to investigate the effects of plant water stress on canopy temperature, to determine the non-water-stressed baseline and to observe diurnal and seasonal variations of crop water stress index (CWSI). Canopy temperature, psychrometric and wind speed data were taken each half-hour, between 09.30 and 15.30 h. Results showed that canopy temperature was higher during the daytime, for both unstressed and stressed plots. A linear regression of canopy-air temperature differential and thevapour pressure deficit (non-water-stress baseline) showed a value of r2 = 0.65. During the stress period, the average canopy temperature of the stressed plot was up to 5.4℃ higher than the unstressed plot. Diurnal and seasonal average of CWSI values showed differences between unstressed and stressed plots, during the stress period.