A multiplicity of mechanisms in the plant kingdom which can contribute to iron efficiency

Abstract

Biochemical, physiological, and anatomical changes, which occur in plants as result of iron stress, have been subject of study in recent years. The evidence indicates that at least some plant materials have the characteristics whether or not they are under iron stress. The same species, when studied in the laboratory, variously undergo changes when transferred from iron‐sufficient to iron‐stress conditions. Some of the changes occur in minutes. Since efficient plants have efficient characteristics, even when not under stress, the changes will be either quantitative or qualitative; relationships are not fully understood. Iron‐stress response involves proton expulsion, redox, citrate buildup in roots, and/or chelator (siderophore) production. Possibly other responses are involved, and even these four named have multiple methods of expression. If all four were involved singly or together in all possible combinations, 15 different mechanisms would be possible (a, b, c, d, ab, ac, ad, bc, bd, cd, abc, abd, acd, bcd, abcd). Since each of the four is expressed in different ways, the possible number of different mechanisms could be many more than 15. A classification of them, according to physiological and ecological implications, is only in its beginning.

Key words:

• Proton expulsion
• redox
• chelators

Notes

The Laboratory of Biomedical and Environmental Sciences is operated for the U.S. Department of Energy by the University of California under Contract No. DE‐ACO3–76‐SF00012.