Micronutrient contents in leaves of sunflower cultivars grown with different boron doses

Althogh boron is essential for crop growth, the amount required differs among plant species. Sunflower (Helianthus annuus L.) requires greater quantities of boron to satisfy its metabolic needs than other cultivated species. The present work was undertaken to evaluate what effects five boron doses of 0, 2.5, 5.0, 7.5 and 10.0 kg B/ha (applied as a spray of boric acid, H3BO3) would have on micronutrient contents in leaves of four sunflower cultivars grown in B-deficient calcareous soils (0.19 B mg/kg) during the 2001 growing season. Boron (B), iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) concentrations were measured in sunflower leaves at the flowering stage. According to the results, the B concentration in the leaves was highly correlated with boron doses, that is, the leaf B content increased in accordance with increasing B doses applied to the soil. Fe, Mn, Cu and Zn concentrations in leaves were not changed by the different B levels. However, leaf Mn, B and Cu concentrations varied with the cultivars. Among the cultivars, TR-4098 had the highest Mn (90.74 mg/kg) and Cu contents (45.95 mg/kg), while AS-615 had the highest B (83.52 mg/kg) and Fe (202.55 mg/kg) concentrations.