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Reza Saeedi, Nematollah Etemadi, Ali Nikbakht, Amir H. Khoshgoftarmanesh, and Mohammad R. Sabzalian

inorganic sources of calcium, e.g., Ca(NO 3 ) 2 .4H 2 O, are applied during winter or early spring production to prevent calcium deficiency ( Dole and Wilkins, 2004 ). Recently, Ca-amino acid chelates have been synthesized and distributed to supply different

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Li-Xiao Yao, Yong-Rui He, Hai-Fang Fan, Lan-Zhen Xu, Tian-Gang Lei, Xiu-Ping Zou, Ai-Hong Peng, Qiang Li, and Shan-Chun Chen

into strategy I or strategy II plants ( Eide et al., 1996 ; Robinson et al., 1999 ; Romheld, 1987 ; Romheld and Marschner, 1986 ). Strategy II plants include grasses with roots that secrete compounds known as phytosiderophores (PS), which chelate Fe

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Uttara C. Samarakoon and James E. Faust

phytotoxicity symptoms. Chelated Ca that contains ethylenediaminetetraacetate (EDTA) can improve Ca absorption at lower Ca concentrations with root uptake ( Nelson and Niedziela, 1998 ), as well as with foliar applications ( Tang et al., 2007 ). The commercial

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Charalambos I. Siminis and Manolis N. Stavrakakis

(III) to the bioavailable ferrous form [Fe(II)] is required before the transmembrane import of iron ( Marschner and Römheld, 1994 ). In strategy II plants (graminaceous species), soil Fe(III) is chelated and transferred by the plant

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James L. Walworth, Scott A. White, Mary J. Comeau, and Richard J. Heerema

acidified and calcareous soil. Chelated Zn fertilizers, such as those made with EDTA, can alter the soil mobility of Zn and more effectively increase levels of bioavailable Zn compared with inorganic Zn fertilizers (Alvarez, 1997). Chelated Zn is less

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Joseph P. Albano and Donald J. Merhaut

Most soluble fertilizers used in floral crop production are formulated with micronutrient metals Cu, Fe, Mn, and/or Zn complexed with synthetic APCA complexones, known commonly as chelating agents like EDTA, DTPA, and EDDHA. These compounds are used

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Joseph P. Albano

as ligands or chelating agents. These compounds, especially EDTA, are widely used in an array of domestic, medical, industrial, and agricultural purposes where complexation of multivalent metals in a system is desired. The primary drawback of

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Joseph P. Albano

Soluble fertilizers are typically formulated with metal-aminopolycarboxylic acids [APCA (i.e., chelating agents)] of Cu, Fe, Mn, and Zn. These metal–APCA complexes, however, are also applied as single-metal chelate solutions to foliage, soil

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B. Castillo, D.L. Madhavi, and M.A.L. Smith

Interaction between irradiance levels (5–40 mMm–2–s–1) and iron chelate sources (FeNa2EDTA and FeNaDTPA) on the establishment, growth, and proliferation of shoot tips of Carica papaya were tested. Reduced irradiance level (5 mMm–2–s–1) enhanced the establishment of shoot tips regardless of the source of iron chelate tested. At higher irradiance levels (30 and 40 mMm–2–s–1), presence of FeNaDTPA in the medium enhanced establishment of shoot tips. Continuous or alternating light/dark (16/8 h) photoperiods at high irradiance levels had no effect on the establishment or growth of the culture. At higher irradiance levels, the cultures produced smaller leaves as compared to lower irradiance levels. Low irradiance and FeNa2EDTA was preferred during the proliferation stage.

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Joseph P. Albano and William B. Miller

Iron chelate photodegradation is a problem in tissue culture where limited soluble Fe in agar reduces callus tissue growth. Our objectives were to determine if Fe chelate photodegradation occurs in commercial fertilizers used in greenhouse plant production and, if so, the effects on plant Fe acquisition. Commercial 20N–10P–20K soluble fertilizers containing Fe-EDTA were prepared as 100x stocks based on a 100 mg N/liter (1x) concentration. A modified Hoagland's solution with Fe-DTPA was prepared as a 10x stock based on a 200 mg N/liter (1x) concentration. Samples then were kept in darkness or were irradiated with 500 μmol·m–2·s–1 from fluorescent and incandescent sources for ≤240 hours. Soluble Fe in the irradiated commercial fertilizer solutions decreased 85% in 240 h. Soluble Fe in the Hoagland's solution, prepared in the lab, decreased 97% in 72 h. There was no loss in soluble Fe in any dark-stored treatment; demonstrating photodegradation of Fe-chelates under commercial settings. Excised roots of marigold (Tagetes erecta L.), grown hydroponically in the irradiated solutions, had Fe(III)-DTPA reductase activity 2 to 6 times greater than roots of plants grown in solutions kept in darkness. Plants growing in irradiated solutions acidified the rhizosphere more than plants growing in solutions kept dark. The increase in Fe reductase activity and rhizosphere acidification are Fe-efficiency reactions of marigold responding to the photodegradation of Fe-chelates and subsequent decrease in soluble Fe in both commercial fertilizers and lab-prepared nutrient solution.