Ferrous iron determination in plant tissue

Abstract

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.

Key words:

• Iron nutrition
• Sorghum bicolor (L.) Moench
• Iron chelating agents
• Leaf extractions
• Mineral nutrition