Table III.

The pH of xylem sap and leaf apoplastic fluid of young fully expanded sunflower leaves as affected of N form and nutrient solution pH

Data are means ± sd of four replications. Significant differences (P < 5%) between treatments are indicated by different letters.

Treatments Xylem sap Leaf apoplastic fluid
NO3-; pH 5.0 (green) 5.6 ± 0.1a 6.7 ± 0.1a
NO3-, 40 mm; pH 5.0 (green) 5.8 ± 0.2a 6.6 ± 0.0a
NO3-; unbuffered (chlorotic) 5.8 ± 0.1a 6.7 ± 0.0a
NH4+; pH 5.0 (green) 5.7 ± 0.2a 6.4 ± 0.1a
NH4+; pH 7.5 (chlorotic) 5.6 ± 0.1a 6.5 ± 0.1a
NH4NO3; unbuffered (green) 5.8 ± 0.1a 6.5 ± 0.1a
NH4NO3; pH 7.5 (chlorotic) 5.7 ± 0.2a 6.4 ± 0.1a