Table V.

Effects of N forms and nutrient solution pH on Fe-binding forms in cell walls of sunflower leaves

Total cell wall Fe was calculated as the sum of strongly bound and weakly bound fractions. Data are means ± sd of four replications. Significant differences (P < 5%) between treatments are indicated by different letters.

Treatments Total Fe Weakly Bound Fe Strongly Bound Fe
μmol g-1 dry wt
NO3-; pH 5.0 (green) 3.4 ± 0.9a 2.2 ± 0.7a 1.2 ± 0.1a
NO3-, 40 mm; pH 5.0 (green) 3.9 ± 1.3a 2.6 ± 0.8a 1.3 ± 0.5a
NO3-; unbuffered (chlorotic) 1.7 ± 0.4b 1.2 ± 0.4b 0.5 ± 0.1b
NH4+; pH 5.0 (green) 4.2 ± 2.1a 2.8 ± 1.5c 1.4 ± 0.6a
NH4+; pH 7.5 (chlorotic) 2.4 ± 0.3c 1.2 ± 0.3b 1.2 ± 0.1a
NH4NO3; unbuffered (green) 3.8 ± 0.9a 2.5 ± 0.6a 1.3 ± 0.5a
NH4NO3; pH 7.5 (chlorotic) 1.9 ± 1.0b 1.5 ± 0.5b 0.4 ± 0.2b