Effect of copper and molybdenum in nutrient solution on Cu, Mo, Fe, Mg, Ca, Zn, Na, K status in sunflower

Interactions of mineral elements in crops strongly affect their nutritional value and the yield. Within the context of ruminants feeding, ensuring Cu:Mo molar ratio in the range from 2:1 up to 20:1 has been considered. In this work, the impact of different Cu and Mo concentrations applied in nutrient solution of hydroponically grown Helianthus annuus was evaluated in terms of the seedlings growth and the status of Cu, Mo, Fe, Zn, Mg, Ca, K, Na. Nine groups of plants were obtained using concentration range 0.1-10 mu mol L-1 for Cu and 0.1-50 mu mol L-1 for Mo. Biomass in each treatment was assessed and eight elements were determined in roots and in aerial parts by microwave plasma atomic emission spectrometry (MP-AES). Several synergic and antagonistic interactions of Cu and/or Mo with other six mineral nutrients during uptake and root-to-shoot transport were observed. Regarding the feasibility of tuning Cu and Mo in medium to meet ruminants requirements, each of eight treatments was compared against control plants that were obtained using typical Cu and Mo concentrations in medium (0.44 and 0.70 mu mol L-1, respectively). For ten-fold increased Cu concentration in medium (treatment 6), the most favorable Cu:Mo ratio was afforded (8.8:1 in roots and 17:1 in aerial parts) when compared with the control plants (1.8:1 and 20:1, respectively). Further, the concentrations of both elements in aerial parts were within ranges reported for forage; seedlings growth was not affected and concentrations of six other elements were practically unchanged when compared with controls.