Girdling experiments
To test for an effect of reduced phloem transport during drought on foliage hormone levels, prior to drought a single, large branch on three individuals was girdled. Branches were girdled by carefully removing two to three cm of periderm just above the intersection of a side branch and the main, leading stem. Once periderm was removed a hydrogel was applied to the xylem (Tensive, Parker Labs, Fairfield, NJ, USA). Samples from girdled and non-girdled branches were harvested concurrently to determine Ψl using a Scholander pressure chamber and to collect a subsample of tissue for hormone quantification.