*2.1. Titratable Acidity*

Titratable acidity levels for 10 days old cotyledons were at approximately 50–60 μeq gFW−<sup>1</sup> (FW = Fresh Weight; Figure 1). At 10 days, the control groups and water-stressed leaves showed a slight acid fluctuation of 10–20 μeq gFW−<sup>1</sup> from a.m. to p.m. (Figure 1). There was no significant difference between a.m. and p.m. acid levels. At 20–25 days old, cotyledons, under control conditions, there was no acid fluctuation observed from a.m. to p.m. levels. Under water stress, cotyledons showed a small significant titratable acid fluctuation from the morning to the evening (Figure 1). Continued water stress to 7 days of the 20–25 days old cotyledons induced a large and significant acid fluctuation of 83 μeq gFW−<sup>1</sup> in both the cotyledons and primary leaves of *P. grandiflora* (Figure 2). The a.m. acid levels had increased to more than double the control cotyledons.

**Figure 1.** Titratable acidity of *Portulaca grandiflora* in 10 days and 25 days old cotyledons under control and 3 days water-stress conditions. Bars represent the means (SEM). For 10 days old, N = 9–11 leaves per treatment; 25 days old, N = 8–13 leaves per treatment; and \* indicates a significant difference between a.m. and p.m. acid levels for 25 days old treatment. Con = Control; WS = Water Stress for all figures.

**Figure 2.** Diurnal titratable acidity levels in cotyledons and primary leaves of *P. grandiflora* after 7 days of water stress. Bars represent the means (SEM). Bars with different letters are significantly different (*p* < 0.05, N = 4).
