Physiological and morphological traits associated with increased water use efficiency in the willow-leaf peach

A chimeric, willow-leaf mutation of a standard peach [Prunus persica (L.) Batsch.] phenotype was evaluated for its water use efficiency (WUE). The willow-leaf phenotype had greater WUE than its standard-leaf parent under both nonstressed and well-watered conditions, and this was supported by isotopic carbon discrimination. Under water-stress conditions, willow-leaf trees developed less water potential gradient from the roots to the leaves. The mechanisms associated with increased WUE by the willow-leaf phenotype include a reduced water potential gradient within the plant and uncoupling of the leaf from the aerial environment. Willow-leaf peach trees in seedling populations, descended from a different willow-leaf parent, also had reduced carbon isotopic discrimination than did sibling standard leaf seedlings.