INFLUENCE OF IRON-CHELATES ON TRACE ELEMENT UPTAKE FROM TWO CALCAREOUS SOILS AND THE ACTIVITY OF OXYGEN-SCAVENGING ENZYMES IN LETTUCE

Abstract

A pot experiment was carried out to determine the ability of lettuce (Lactuca sativa cv. ‘Waldmann's dark green’) to acquire iron (Fe) from Fe-ethylenediaminedisuccinic acid [EDDS, both as an isomeric mixture, EDDS(mix), and (S,S)-EDDS], Fe-ethylenediaminetetraacetic acid (EDTA) and Fe-ethylenediimonobis(2-hydroxyphenyl)acetic acid (EDDHA) in two calcareous soils and consequent effect on the activity of reactive oxygen species scavenging enzymes. Probably due to the rapid biodegradation of [S,S]-EDDS, EDDS(mix) provided Fe to lettuce more efficiently. Iron-EDDS(mix) and Fe-EDDHA were equally efficient in increasing Fe concentration in lettuce. The activity of superoxide dismutase (SOD) was not affected by Fe deficiency and the activity of copper (Cu) and zinc (Zn) containing SOD (Cu/ZnSOD) was dependent on lettuce Zn concentration. Ascorbate peroxidase and guaiacol peroxidase activities were increased by Fe-EDDHA, probably due to the steady supply of Fe. Physiologically active Fe pool for lettuce was equally provided by Fe-EDDS(mix) and Fe-EDTA.

Keywords:

• biodegradation
• nutrient uptake
• EDDS
• iron deficiency
• peroxidase
• superoxide dismutase

ACKNOWLEDGMENTS

I acknowledge the contributions of Prof. Antti Jaakkola and Dr. Reijo Aksela in planning the experiment and of Prof. Markku Yli-Halla for his comments on the manuscript. I also thank laboratory technician Katja Halonen for skilfull technical assistance, and M.Sc. Reetta Puska from Kemira Agro Oy for providing the calcareous soils. The financial support of Kemira Agro Oy, the National Technology Agency of Finland, and the Foundation of August Johannes and Aino Tiura is gratefully acknowledged.