Fig. 4.

Titratable acidity in stems of Portulaca cryptopetala at the end of the 12 h light period (red) and the end of the 12 h dark period (blue) in plants that were well-watered (left-hand column), droughted (middle column; 10 d without irrigation), and droughted and rewatered (right-hand column; 2 d with irrigation). The data are expressed on a fresh mass basis (A) and a dry mass basis (B). Mean ±SD (n=5 stems; at a given time point each stem was harvested from a different plant). The numeric values shown above the bars are P values (one-tailed t-test). Bold letters indicate that the values at the end of the dark period were significantly greater than those at the end of the day at P≤0.05.