Iron Toxicity Stress Causes Bronze Speckle, a Specific Physiological Disorder of Marigold (Tagetes erecta L.)

Abstract

<jats:p>A specific physiological disorder, bronze speckle (J.P.A.'s nomenclature), was consistently induced in `First Lady' and `Voyager' marigold with Fe-DTPA concentrations greater than 0.018 m<jats:sc>m</jats:sc> Fe-DTPA (1 ppm) applied to a soilless medium. The disorder was characterized by specific symptomology distinguished visually by speckled patterns of chlorosis and necrosis, and downward curling and cupping of leaves. The percentage of total leaf dry weight affected with symptoms generally increased with increasing Fe-DTPA treatments. Symptomatic leaf tissue had a greater Fe concentration than corresponding asymptomatic leaf tissue. Leaf Mn concentrations in symptomatic and asymptomatic tissue were similar. In `First Lady', older leaf tissue accumulated more total Fe and was associated with more severe symptoms than younger tissue. Media leachate Fe concentrations increased over 6 weeks and were larger at greater Fe-DTPA treatments. Adjustment of nutrient solution pH to 4.0, 5.25, or 6.5 did not alter media pH, nor did it prevent disorder symptoms. Application of Fe-DTPA containing nutrient solution to a soilless medium resulted in leachate Fe levels 3 times greater than for FeSO<jats:sub>4</jats:sub> treatments. Chemical names used: ferric diethylenetriaminepentaacetic acid, monosodium salt (Fe-DTPA).</jats:p>

Effect of Elevated Iron on Ultraviolet Light-Absorbing Compounds of Cucumber Cotyledon and Leaf Tissues

“…Iron(II) toxicity in plants may produce foliar necrotic pitting, speckling and distinctive brown or bronze lesions attributed to coalesced tissue necrosis (1,4). In the present study, a brownish discoloration of the leaf disks was observed at FeSO 4 · 7H 2 O levels above 0.175 mM (pH 4.5-6.0).…”

“…The phytotoxicity of iron is apparently enhanced at lower soil pH (1,4). In an attempt to identify the hydrolysis species of Fe(II), which modified the phenolic compounds, the effect of pH on the responses of individual UV light-absorbing compounds to elevated Fe(II) was determined.…”

“…A majority of the research has considered primarily the mechanisms by which plants avoid iron deficiency stress, investigating processes that facilitate iron uptake (2,3). However, iron efficient plants and plants exposed to certain environmental conditions, such as waterlogging, may accumulate foliar iron in excess of their physiological requirements and display distinctive leaf lesions (1,(4)(5)(6)(7). Excess iron stress may significantly reduce the yield of important crop plants (1).…”

Physiological Disorder of Rice Associated with High Levels of Iron in Growth Medium

“…Application of Fe in the growth medium resulted in decreased total soluble protein in leaves (Table 2). Phytoferritin, an iron storage protein is induced by Fe and is reported to function as a cellular Fe buffer (Albano et al, 1996). A resistant variety may accumulate more amount of phytoferritin, which forms complexes with Fe, and, thus Fe toxicity symptoms are not observed in resistant varieties.…”

Phytotoxicity of Several Iron Fertilizers and Their Effects on Fe, Mn, Zn, Cu, and P content of African Marigolds and Zonal Geraniums

“…Several synthetic chelating agents with high affinities for Fe have been shown to be much more effective in correcting Fe chlorosis in a wide range of plants (Martens and Westermann, 1991). However, some of these products can be phytotoxic to plants, and marigolds and zonal geraniums are reported to be especially sensitive to Fe toxicity (Albano et al, 1996;Bachman and Miller, 1995). The purpose of this study was to determine the relative phytotoxicity of several commercially-available Fe fertilizers and their effects on the uptake of Mn, Zn, Cu, and P in seedling marigolds and zonal geraniums.…”