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

Abstract

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, hybrid, NB 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 NB 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.

Notes

Present address: Department of Botany and Plant Sciences, University of California, Riverside, CA 92521–0124.