Some physiological aspects of iron deficiency in plants

Abstract

This paper is a brief review and interpretation of seme of the information presented at the seminar reported in this volume. Dicot plants tend to excrete H⁺ from roots when Fe deficient but monocots do not. This can be interpreted as greater cation to anion uptake ratios in the dicots than in monocots. The fact that dicot roots excrete considerable H⁺ when Fe deficient explains why dicot roots result in much Fe chelate splitting before Fe uptake. Iron then is taken up by the plant with chelating agent remaining in the culture medium. Without the H⁺ production the chelate is more stable and Fe tends to be taken up by plants as Fe chelate but more sluggishly than when Fe chelate is split. With monocots then, which do not tend to excrete H⁺, Fe chelates are a relatively poor source of Fe and often lead to Fe deficiency in the presence of chelated Fe. Previous studies of the effect of pH on Fe and chelating agent uptake by plants tends to confirm these conclusions. From a theoretical point of view, plants with symbiotic N fixing relationships should be quite resistant to Fe chlorosis. High bicarbonate levels are conducive to the development of Fe deficiency because they circumvent the plant's attempts to make physiological adjustments to low Fe supplies.

Key words:

• Iron deficiency
• organic acids
• chelate
• cation‐anion balance
• nitrate assimilation