Resumen de Responses of five almond cultivars to irrigation: Photosynthesis and leaf water potential

J. Gomes Laranjo, J.P. Coutinho, V. Galhano, Victor Cordeiro

• In the Trás-os-Montes region, almond orchards are usually planted in the dry soils on the upper valley of the Douro river and are typically cultivated under non-irrigated conditions, leading to low yields. This study aimed to compare the physiological responses of five almond varieties (Francoli, Ferragnès, Glorieta, Lauranne and Masbovera) growing under non-irrigated and irrigated conditions. In irrigated conditions, all cultivars had higher photosynthetic rates, with maximum rates in a range of 10�12 µmol CO2 m-2 s-1. Study of daily photosynthesis (June�August) indicates that, irrigated plants showed maximal values at 11 h (32 °C), while in water stressed ones highest values were found at 9 h (28 °C). The irrigation induced an increase in photosynthesis of around 173% in Lauranne, 187% in Francoli, 204% in Glorieta, 266% in Masbovera and 331% in Ferragnès. In relation to values of water potential that allow half-rate of photosynthesis (?w50), they were calculated as -2.95, -2.50, -3.10, -3.20 and -3.30 MPa for Ferragnès, Glorieta, Masbovera, Francoli and Lauranne, respectively.