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these infrequent climate extremes. Under water-limited conditions, desert evergreens must quench excess energy from saturating light levels, in part because pro-longed stomatal closure limits carbon fixation as an effective From July 20 to 25, 2002, we used a Scholander-type pressure chamber (PMS Corvallis, OR) and a pulse-amplitude-modulated (PAM) chlorophyll fluorimeter (FMS-2, Hansatech, Ltd., Norwich, UK) to determine differences in ecophysiological performance of two evergreen desert shrubs, creosotebush (Larrea tridentata; hereafter referred to as Larrea) and jojoba (Simmondsia chinensis) under extreme drought conditions. Larrea and jojoba can maintain positive photosynthetic rates under hot and dry condition