Table 5.
Titratable acidity in Bulnesia retama plants at varying drought intensity.
| Organ | Water potential | Titratable acidity (µmol H+ g−1 FW) |
|||
|---|---|---|---|---|---|
| w (MPa) | Afternoon | Dawn | ΔH+ | P-value | |
| Measured values - l eaf | |||||
| Well watered | −0.6 ± 0.01 | 89.1 ± 6.6 | 86.3 ± 6.1 | −2.8 ± 8.9 | P = 0.62 |
| Moderate drought | −2.6 ± 0.1 | 91.3 ± 7.4 | 138.1 ± 15.0 | 46.9 ± 22.2 | P = 0.08 |
| Measured values - s tem | |||||
| Well watered | −0.6 ± 0.01 | 114.6 ± 11.4 | 137.0 ± 21.8 | 22.4 ± 10.6 | P = 0.046 |
| Moderate drought | −2.4 ± 0.1 | 131.0 ± 20.9 | 229.7 ± 43.0 | 98.6 ± 23.7 | P = 0.013 |
| Severe drought | −3.5 ± 0.2 | 148.5 ± 21.4 | 159.2 ± 26.6 | 10.6 ± 12.2 | ns |
| Extreme drought | −5.0 ± 0.3 | 224.2 ± 35.4 | 154.9 ± 21.3 | −69.3 ± 41.3 | ns |
| Literature values | Mean ± s.d. | ||||
| Agave americana | – | 18.1 ± 4.6 | 331.1 ± 28.9 | 313 | – |
| Calandrinia flava | |||||
| Watered | – | – | – | 13.1 ± 2.0 | – |
| Droughted | – | – | – | 27.6 ± 2.2 | – |
| Re-watered | – | – | – | 24.3 ± 7.0 | – |
| Calandrinia volubilis | |||||
| Watered | – | – | – | 3.2 ± 1.9 | – |
| Droughted | – | – | – | 82.2 ± 11.6 | – |
| Re-watered | – | – | – | 23.8 ± 2.7 | – |
Titratable acidity of leaf or stem tissue was determined in the afternoon (16:00 h) and at dawn (07:00 h). Values are the mean ± s.e.m. (n = 3 plants per treatment). Differences between ΔH+ means were tested using Student’s one-tailed t-test, where all ΔH+ values from a given plant were pooled to give one value per plant for the category of water status shown. For comparison, values from Winter and Smith (2022) for strong CAM Agave americana (Asparagaceae) and from Hancock et al. (2019) for C3 + CAM Calandrinia flava and C. volubilis (Montiaceae) are shown. FW is fresh weight.