Iron, sulfur, and chlorophyll deficiencies: A need for an integrative approach in plant physiology

Abstract

Green plants deficient in nitrogen, sulfur, or iron develop a similar yellow coloration. In each case, the yellow coloration is accompanied by a lowered chlorophyll concentration. This review attempts to collate some of the biochemical information concerning these three seemingly diverse nutritive deficiencies and bares a need for a more integrative approach to plant physiology. The biochemical and biological roles of nitrogen, sulfur and iron in living systems are examined, with emphasis on sulfur and iron. Mechanistically, iron and/or sulfur are highly reactive components of many enzymes. Indeed, iron and sulfur sometimes form Fe2S2, Fe3S4, or Fe4S4 clusters which are very active electron transfer agents. Recently, iron‐sulfur clusters have been reported to serve as sensors of oxidative stress, to couple photosynthesis with several metabolic pathways, to participate in the reduction of sulfite and nitrite, and to participate in regulation of gene expression. Thus, there are several mechanisms by which a deficiency of nitrogen, sulfur, or iron could produce the same low‐chlorophyll, yellow phenotype in plants. Unless the interactions and coordination of the various pathways connected to chlorophyll synthesis are elucidated, it is unlikely that we will select the quickest and most direct path to plant improvement.

Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils

“…This is partly attributable to iron deficiency in a range of different plant species (Mishra and Kar, 1974;Ma and Nomoto, 1993;Römheld and Marschner, 1986;Wallace et al, 1992) in heavy metal contamination soil. Furthermore, the low iron content of plants that are grown in the presence of high levels of heavy metals generally results in these plants becoming chlorotic, since iron deficiency inhibits both chloroplast development and chlorophyll biosynthesis (Imsande, 1998). However, microbial iron-siderophore complexes can be taken up by plants, and thereby serve as an iron source for plants (Bar-Ness et al, 1991;Reid et al, 1986;Wang et al, 1993).…”

“…A number of PGPR, which stimulate root growth of different plant species including Indian mustard (Burd et al, 1998;Belimov et al, 2001), contain the enzyme ACC deaminase, which hydrolyses and decreases the amount of ACC, an ethylene precursor of the plant hormone ethylene, in plants and, as a result, to decrease ethylene biosynthesis by plants 1998;Hall et al, 1996). The model which represents how a PGPR bound to either a seed or plant root lowers the ethylene concentration and thereby prevents ethylene inhibition of root elongation was previously proposed by Glick et al(1998).…”

Iron Deficiency-Induced Secretion of Phenolics Facilitates the Reutilization of Root Apoplastic Iron in Red Clover

“…However, despite the fact that the total Fe content in soils usually far exceeds plant requirements for Fe, its bioavailability in the soil is often severely limited (Guerinot and Yi, 1994), particularly in calcareous soils that occupy 30% of the earth's surface (Vose, 1982). Therefore, despite being the fourth most abundant element in the earth's crust, Fe deficiency is one of the most limiting factors for crop production and induces chlorosis in about 30% of crops worldwide (Imsande, 1998). Fe-efficient plants undergo both morphological and physiological changes in response to Fe deficiency, including enhanced root exudation of organic compounds when grown under Fe-limited conditions (Marschner, 1995).…”

Phytoextraction of soil cadmium and zinc by microbes-inoculated Indian mustard (Brassica juncea)

“…Elevated levels of metals in the soil lead to excessive absorption by roots and translocation to shoots, and might have resulted in impaired metabolism and reduced plant growth (Foy et al 1978;Bingham et al 1986;McGrath et al 1995). Apart from this, the high concentration of Zn and Cd in the soil might have competed out iron, leading to its deficiency and thus inhibiting both chloroplast development and chlorophyll biosynthesis in plant (Imsande 1998). A relatively moderate reduction in plant growth due to increased concentration of Zn in soil, as observed in the present investigation, highlighted it as a plant nutrient, unlike Cd.…”