Interactions of iron nutrition and symbiotic nitrogen fixation in peanuts

Abstract

Nitrogen fixation and Fe‐deficiency stress response are two processes involving chemical reduction reactions in the root. It is possible that these processes could enhance one another in nodulated peanuts (Arachis hypogaea L.). The objective of this study was to determine the interactions of Fe nutritional stress, nodulation, and N₂ fixation in peanuts. Plants were grown in solution culture which allowed careful control of levels of inorganic nitrogen (NO₃ ^‐) and Fe. To monitor plant Fe‐stress response, nutrient solution pH and reductant were measured daily. Nitrogenase activity was measured periodically by the acetylene reduction technique and Fe contents of leaf tissue at each sampling time were determined. Iron‐stress response was exhibited by peanut varieties 71–234 and Valencia grown in Fe‐free nutrient solutions and the response was stronger in nodulated than in non‐nodulated plants. Acetylene reduction was greatest in peanuts grown in Fe supplemented solutions.

Key words:

• Iron‐stress response
• Rhizobium
• chlorosis
• Arachis hypogaea