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Title:Induction of growth and pigmentation changes by hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in angiosperms
Author(s):Hagen, Frank
Director of Research:Dawson, Jeffrey O.
Doctoral Committee Chair(s):Dawson, Jeffrey O.
Doctoral Committee Member(s):Seigler, David S.
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)
Pigmentation changes
Abstract:Eighteen angiospermous species of plants were assayed for tolerance of Hexahydro- 1,3,5-trinitro-1,3,5-triazine (RDX). Plants were grown in RDX soil treatments of 100, 500, and 1000 mg per kg for 60 days. Tolerance of RDX, expressed as a mean percentage of control dry mass, was greatest for Amaranthus retroflexus L. (pigweed) (110%-166%), Ipomoea jaegeri Pilg (morning glory) (57%-146%), and Coronilla varia L. (crown vetch) (61%-82%). Tolerance of RDX was least for Eschscholzia californica Cham. (California poppy) (6%- 29%), Datura stramonium L. (jimson weed) (16%-38%), and Amaranthus caudatus L. (love lies bleeding) (16%-21%). Results indicate that soil RDX is toxic at levels of 100 to 1000 mg per kg, similar to levels found in soils on military sites. RDX reduced root biomass more than shoot biomass and reduced the plant's cellular water content, yielding leaves that were thin and malleable. Considerable variation in tolerance to RDX was found within and among the species and cultivars tested, but not at the level of plant family or genus, indicating the individualistic existence of genetic traits imbuing tolerance to RDX. An 15N isotopic shift towards that of synthetic RDX in leaf tissue of four species of plants grown in RDX-dosed soils indicated that applied RDX was consistently taken up into the plants. Quantities of RDX breakdown compounds occurred only at levels near the lower detection limit by HPLC. Breakdown compounds were found in leaf tissue of a subset of four angiospermous species, suggesting that RDX breakdown compounds do not occur in large pools in plant tissue because of rapid turnover in soil or plant, or spontaneous degradation of unstable primary breakdown compounds. The mean amounts of RDX taken up per plant for selected forb species, ranked from greatest to least amount, and with the corresponding soil RDX concentrations were: C. varia (36.0 mg per plant at 1000 mg per kg), E. californica (8.8 mg per plant at 500 mg per kg), and Tropaeolum majus L. (nasturtium) (6.0 mg per plant at 500 mg per kg). These results indicate that some angiospermous plants have superior potential for use in phytoremediation of RDX contaminated soils. Sida spinosa L. (prickly sida), a member of the Malvaceae family, was the only plant that produced red pigmentation at leaf margins and interveinal chlorosis in greenhouse studies. A threshold level of 160 mg per L of RDX in soil solution was necessary for the red color change to be visible. This coloration occurred only at the normal time of flowering, approximately 70 days after seed germination (60 days of growth in soil at various RDX treatment levels). The red pigments in S. spinosa are probably anthocyanins, the only red pigment occurring in plants of the family Malvaceae. Three other members of the Malvaceae family iii were exposed to the same RDX-treatment regimes as S. spinosa but did not produce red pigmentation of leaf margins at the time of flowering. Varying plant densities in a pot; soil dosing with TNT; mechanical injury to leaves; hormonal treatment with ABA, gibberellins and cytokinins; water deprivation; flooding; and supplying nitrogen fertilizer all failed to induce visible red pigmentation of flowering S. spinosa leaf tissue in plants not treated with RDX. Nor did these environmental/chemical treatments induce any interactions with respect to red pigmentation of plants grown in RDX treated soil, with the exception of a one-week extended period of pigmentation in plants that received flooding treatments. Results indicate potential for the use of S. spinosa reddening as a bioindicator to identify and assess soil and water contaminated with RDX under either controlled or field conditions
Issue Date:2013-08-22
Rights Information:Copyright 2013 Frank Hagen
Date Available in IDEALS:2013-08-22
Date Deposited:2013-08

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