Table 2.
Intracellular sugar levels of, and sucrose uptake by, 18 DAF RR pea cotyledons cultured for 2 d on specified soluble sugar species
| Parameter measured | 300 mM sugar added to MS culture medium |
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| Sucrose | Palatinose | Glucose | Fructose | No sugar | |
| Intracellular concentration (mM) of: | |||||
| Sucrose | 36.8±1.8 | 9.2±1.2 | 12.4±0.8 | 12.1±1.1 | 6.4±0.7 |
| Glucose | 8.2±0.3 | 5.3±0.3 | 12.0±0.7 | 7.8±0.7 | 4.4.±0.2 |
| Fructose | 6.1±0.3 | 3.2±0.2 | 4.7±0.3 | 9.7±0.6 | 2.6±0.5 |
| Transporter activity (μmol cm−2 h−1) of: | |||||
| Sucrose facilitators | 0.45±0.09 | 0.44±0.13 | 0.45±0.10 | 0.50±0.12 | 0.40±0.09 |
| Sucrose/proton symporters | 0.16±09 | 0.33±08 | 0.33±10 | 0.27±0.05 | 0.31±0.08 |
Intracellular sugar concentrations were determined in protoplast saps extracted from freeze-dried cotyledons. Influx of [14C]sucrose uptake across the abaxial epidermis was determined for sister cotyledons pre-treated with ±5 mM DEPC to estimate activities of sucrose/proton symporters (total flux minus DEPC-insensitive flux) and sucrose facilitators (DEPC insensitive flux). Means ±SE of four replicates per treatment.