DIURNAL COURSE OF CANOPY TEMPERATURE AND LEAF WATER POTENTIAL OF SORGHUM (SORGHUM-BICOLOR L MOENCH) UNDER A MEDITERRANEAN CLIMATE

This paper reports the diurnal behaviour of canopy temperature and lea f water potential of Sorghum bicolor L. Moench in a field experiment c onducted in 1990 and 1991 on a deep soil at Montpellier (France). The crop exhibits the typical diurnal trends in its leaf water potential a nd canopy temperature. The predawn values of leaf water potential were high in both well watered and stressed treatments (-0.2 to -0.5 MPa) and the difference in values between the two treatments were very smal l. However, minimum values were observed at solar noon and the differe nces in values observed at this time between the two treatments were a s high as 1 MPa. Canopy temperature as well as canopy-air temperature difference were considerably higher in stressed treatment than in well watered treatment during the daytime. High correlation in the linear relationship between canopy-air temperature difference (T(c) - T(a)) a nd the air saturation vapor deficit for the well watered plot was obse rved.