Fig. 5. Mean diurnal C exchange rates of well-watered (W) and water-stressed (D) guayule in February 2004. Diurnal measurements were taken an average of 4 d after irrigation of the water-stressed plants. Carbon exchange measurements were recorded every 2 h beginning at 0700 and ending at 1700 h. Measurements were taken on eight plants in each irrigation treatment (two plants in each of four replications). The vertical bar indicates ± standard error.