Role of chelahon by ortho dihydroxy phenols in iron absorption by plant roots

Abstract

Under conditions of iron stress, certain higher plants are able to exude ortho-dihydroxyphenols (including caffeic acid) into the root medium. These compounds can reduce ferric iron to the more soluble ferrous form. By the use of radioactive 14 C we have shown that caffeic acid (or a degradation product) can be reabsorbed by plant roots (Hordeum vulgare) and that absorption of ferrous iron can be enhanced several-fold by the presence of the caffeic acid. The finding is attributed to the chelation of ferrous iron and movement of the chelated species into the roots. An analagous mechanism in stressed microorganisms for enhancing availability of ferric iron by means of chelation has been reported previously.

Relative effects of macroinvertebrates and habitat on the chemistry of litter during decomposition

“…In summary, our data demonstrate that macroinvertebrates and local site conditions can both contribute to changes in the chemistry of litter during decomposition. While our results are limited to the first twelve months of decomposition, they are significant because early changes in the chemistry of litter are known to influence a range of subsequent ecological processes including colonization of litter by microarthropods (Anderson 1973;Pereira et al 1998), rates of nitrogen mineralization and immobilization (Northup et al 1995;Schimel et al 1996Schimel et al 1998, the formation of humic acids (Schnitzer et al 1984), iron sequestration and deficiency in soil (Julian et al 1983;Kuiters and Mulder 1993) and allelopathic effects upon other plant species (Gallet 1994;Wallstedt et al 2000). The degree to which macroarthropod-mediated changes in litter chemistry influence these processes will be the subject of future work in this system.…”

“…For example, low C:N ratios and low concentrations of polyphenolics favor consumption by, and population growth of, some invertebrate decomposers (Satchell and Low 1967;Maity and Joy 1999;Zimmer and Topp 2000). Indeed, the loss, transformation or leaching of phenolic compounds during decomposition can have a range of effects upon soil and plant communities including subsequent colonization of litter by arthropods (Anderson 1973;Pereira et al 1998), rates of nitrogen mineralization and immobilization (Northup et al 1995;Schimel et al 1996Schimel et al , 1998, the formation of humic acids (Schnitzer et al 1984), iron sequestration and deficiency in soil (Julian et al 1983;Kuiters and Mulder 1993) and allelopathic effects upon other plant species (Gallet 1994;Wallstedt et al 2000).…”

Traits of fluorescent Pseudomonas spp. involved in suppression of plant root pathogens.

“…Although iron competition among the rhizosphere population has attracted some research attention, it is not yet clear how this affects the iron requirements of plants. Iron deprivation in plants leads to a form of chlorosis (80). It has been reported that the fluorescent siderophore from Pseudomonas sp.…”

Prevention of stress in iron metabolism of plants

“…During rhizosphere acidification, roots may also release organic compounds, probably by leakage of the root cells (Brown & Ambler 1973;Marschner et al 1974;Olsen & Brown 1980). These compounds may stimulate iron uptake by solubilizing soil iron (Julian et al 1983;Hider 1986;Lehmann et al 1987;Erich et al 1987), or by serving as substrates for microbial growth, which lowers the local O 2 level and thus increases the lifetime of ferrous iron.…”