Water Deficit Treatment and Measurement in Apple Trees

Abstract

Water is considered perhaps the most limiting factor for plant growth and productivity (Boyer, 1982), and climate change predicts more frequent, more severe and longer drought periods for a significant portion of the world in coming years. Unfortunately, drought resistance is particularly difficult to measure due in part to the complexity of the underlying biology that contributes to a plant’s ability to cope with water limitations. For example, water deficit is frequently examined by detaching leaves or withholding water for a set period of time prior to tissue collection. Such approaches may elucidate the early stages of drought response but are generally not physiologically relevant for maintenance of drought resistance over a longer period. A more realistic approach is to impose a gradual water limitation with a sustained soil moisture level, particularly in the case of woody perennials. We describe here a protocol that imposes a long-term water deficit under controlled laboratory conditions that allow a molecular biology approach to understanding how woody plants survive severe water limitations. Representative data can be found in Artlip et al. (1997) and Bassett et al. (2014).