Iron deficiency differently affects peroxidase isoforms in sunflower.

Area of Science:

• Plant Physiology
• Biochemistry
• Oxidative Stress

Background:

• Iron is essential for plant growth and development.
• Iron deficiency can lead to various physiological and biochemical changes in plants.
• Peroxidases and hydrogen peroxide are key components of plant oxidative stress responses.

Purpose of the Study:

• To investigate the effect of iron deficiency on peroxidases and hydrogen peroxide content in sunflower plants.
• To determine if iron deficiency induces a cellular oxidative status in sunflowers.
• To analyze the changes in specific (ascorbate peroxidase, APX) and unspecific (peroxidase, POD) enzyme activities.

Main Methods:

• Hydroponic cultivation of sunflower plants with and without iron.
• Measurement of hydrogen peroxide content.
• Enzyme activity assays for APX and POD (guaiacol and syringaldazine-dependent).
• Analysis of extracellular and intracellular peroxidases.
• Electrophoretic separation and cytochemical localization of peroxidase isoforms.

Main Results:

• Iron-deficient (-Fe) sunflower leaves showed significantly increased H2O2 content.
• Extracellular APX activity decreased, while POD activity showed varied responses depending on the substrate and binding fraction.
• Intracellular guaiacol-POD and APX activities significantly decreased.
• Electrophoresis and cytochemistry confirmed reduced peroxidase activity and isoform changes.

Conclusions:

• Iron deficiency induces a secondary oxidative stress in sunflower plants, evidenced by elevated H2O2 levels.
• Different peroxidase isoenzymes are affected to varying extents by iron starvation.
• Despite oxidative stress, sunflower plants likely maintain protection against severe oxidative damage due to limited iron for the Fenton reaction.