Iron deficiency studies of sugar beet using an improved sodium bicarbonate-buffered hydroponic growth system

A sodium bicarbonate (NaHCO3)-buffered hydroponic growth system was developed that simulates alkaline soil growth conditions necessary to screen sugar beet genotypes for iron (Fe) efficiency character. Three genotypes (NB1, NB4, and F-1 hybrid, NE 1xNB4) with differing capacities for Strategy I Fe responses were phenotyped successfully using this system. Genotypes NB1 and NB1xNB4 are Fe efficient, while NB4 is Fe inefficient. It was demonstrated that 5 mM NaHCO3 provided buffering within an optimal range (pH 7.3 - pH 6.3) for the duration of-Fe treatments, promoted enhanced H+ extrusion, and increased the in vivo capacity for Fe3+-chelate reduction (Fe3+-chelate reductase [FCR] activity), especially in the roots of the Fe efficient genotypes. The same concentrations of NaHCO3 did not interfere with Fe supply to +Fe control plants of any genotype. The in vivo capacity for Fe3+-chelate reduction increased over fivefold in both Fe efficient genotypes (NB1 and NE 1xNB4), but just under twofold in the Fe inefficient genotype (NB4). Localization and duration of enhanced Fe3+-chelate reduction capacity were dependent upon the Fe efficiency character of each genotype.