Ferrous iron determination in plant tissue

Experiments were conducted to determine ferrous iron (iron2+, Fe2+) in plant tissues. Iron2+ could be readily extracted from leaf tissue with aqueous solutions of the chelating agents OPh (1,10‐o‐phenanthroline) and PDTS [ferrozine; 3‐(2‐pyridyl)‐5,6‐bis‐(4‐phenylsulfonic acid)‐1,2,4‐triazine]. Iron2+ values did not increase when leaf tissues were extracted more than 30 minutes. The first two extractions of the same tissue yielded higher Fe2+ values than subsequent extractions. After the third extraction of the same tissue, Fe2+ remained relatively constant. Even after seven extractions of the same tissue, some Fe2+ could be extracted which indicated that some iron (Fe) was probably being converted to Fe2+ with each extraction. Initial extractions of the plant material had higher Fe2+ values when extracted with OPh than for PDTS, but subsequent extractions showed similar Fe2+ values for both extractants. Higher Fe2+ values were obtained from fresh leaf tissue than from freeze‐dried or oven‐dried tissue; freeze‐dried and oven‐dried tissues gave similar Fe2+ values. Total Fe measured in these tissues followed: fresh > freeze‐dried > oven‐dried. After the second extraction of the same tissue sample, Fe2+ extracted from each type of tissue preparation were similar.