*4.1. Plant Material*

Seeds of *Portulaca grandiflora* were germinated in flats (Figure 9A,B). All plants grown were irrigated with half-strength Hoagland's solution prior to sampling. The plants were grown under natural light conditions, supplemented with artificial light for a light intensity of 300–400 μmol m−<sup>2</sup> s<sup>−</sup>1.

**Figure 9.** (**A**) Ten-day-old cotyledons growing flat. (**B**) Approximately 20–25 days old *P. grandiflora* seedling with cotyledons and primary leaves.

The day/night temperature in the glasshouse was 27 ◦C/17 ◦C. Seedlings were irrigated daily to maintain high water potential, and water stressed for three days prior to sampling. Experiments were performed when the leaf tissues were 10–14 days old and 22–26 days old post-germination. Leaf samples were taken during the course of the day/night cycle and frozen until assayed for titratable acidity and enzyme activity.
