Response of container-grown photinia to moisture stress

Abstract

Two experiments were conducted to determine the effect of Vapor Gard (VG), an antitranspirant, and moisture stress on shoot water potential of container-grown photinia. In Experiment 1, plants sprayed with VG has less moisture stress than plants with no VG when 24.0 and 27.5 mm of net evaporation occurred prior to watering. Recovery periods for shoot water potential were within 4, 8 and 24 h for photinia stressed to 21.5, 24.0 and 27.5 mm of net evaporation, respectively. Photinia with and without VG were compared in Experiment 2. Shoot water potential and stomatal opening were measured pre-dawn daily (for 9 days) on photinia stressed to −25 and −35 bars pre-dawn shoot water potential before watering. Plants watered daily had a maximum pre-dawn shoot water potential of −3 bars, and watered plants had a higher shoot water potential than stressed plants. Within 8 h after watering, plants with a pre-dawn stress of −25 bars recovered to shoot water potentials of plants watered daily, and stomates closed regardless of VG treatment. Pre-dawn stress to −35 bars resulted in a longer recovery period of shoot water potential (about 36 h). Stomates were closed on plants treated with VG and open on plants not treated with VG. Defoliation (25–75%) occurred on plants stressed to −35 bars and not treated with VG.