*2.2. Enzyme Activity: PEP Carboxylase and NADP-ME*

Ten day old cotyledons showed PEPCase activity higher during the day than at night (Figure 3). Water stress lowered the activity of PEPCase in the 10 days old cotyledons during the day and night. There was a significant difference in daytime activity between the control and water stress at 10 days. At 25 days old, the activity remained high during the day but lower at midnight (Figure 3). In the 25 days old cotyledons, water stress had less of an effect on the overall activity of PEPCase. The PEPCase activity during the day increased in the water-stress plants compared to the control plants (Figure 3). There was no significant differences in PEPCase activity in the 25 days old cotyledons (Figure 3).

**Figure 3.** PEP carboxylase activity of *P. grandiflora* in 10 days and 25 days old cotyledons under control and 3 days water-stress conditions. Bars represent the means (SEM); \* = 10 days Con-Day significantly different from 10 days WS-Day (*p* < 0.05, N = 8–12); 25 days old cotyledons N = 21–25 control plants, N = 8–11 water-stress plants.

The decarboxylase, NADP-Malic Enzyme (ME), showed high daytime activity in both the 10 days and 25 days old control cotyledons (Figure 4). Water stress significantly lowered the NADP-ME activity at 10 days, while at 25 days there was no significant change in the level of activity between the control and water-stressed plants.

**Figure 4.** NADP-ME activity of *P. grandiflora* in 10 days and 25 days old cotyledons under control and 3 days water-stress conditions. Bars represent the means (SEM). N = 6–13. Bars with different letters are significantly different (*p* < 0.05).
