Morphological Responses of Geraldton Wax to Transient Soil-Water Deficit

Abstract

Changes in leaf angle and flower diameter of Geraldton wax (Chamelaucium uncinatum) in response to declining shoot water potential (ψshoot)) were assessed as indicators of plant water status. Leaves and petals in Geraldton wax moved vertically as ψshoot decreased. In cv. Purple Pride, the leaf angle of recently-matured, fully-expanded leaves and the diameter of fully developed flowers showed strong linear correlations with declining ψshoot (r² = 0.90 and 0.94 respectively). The relationships were less strong when applied to almost fully expanded leaves (r² = 0.51) and young flowers (r² = 0.64). Older leaves showed no consistent correlation between leaf angle and ψshoot (r² = 0.01). Similar results were observed in cvv. Alba and Lady Stephanie, but the change in orientation for a given change in ψshoot was smaller in cv. Alba than those observed in cvv. Purple Pride and Lady Stephanie. Vertical orientation of leaves and flower petals in droughted plants could be used as indicators of level of water deficit.