Twanabasu , Bishnu R , Smith, Caleb , Stevens, Kevin J , Venables, Barney J .
Triclosan inhibits arbuscular mycorrhizal colonization in three wetland plants.
The ubiquitous and pseudo-persistent antimicrobial, triclosan(5-chloro-2-[2,4-dichlorophenoxy]phenol; TCS), is one of the most common urban contaminants found in municipal wastewater treatment plant discharges. Potential routes of environmental exposure include not only biota of receiving streams, but also agricultural areas using municipal effluent for irrigation purposes or biosolids for fertilizer and constructed wetlands designed for polishing effluent before delivery to drinking water reservoirs. TCS has been reported to have toxic effects on wide variety of biota and has a mode of action that interrupts lipid biosynthesis in prokaryotes and plants. However, TCS effects on colonization of arbuscular mycorrhizal (AM) fungi in plant roots have not previously been examined in wetland plants. Mycorrhizal fungi are common symbionts found in over 90% of terrestrial plants and are now recognized to play an important role influencing plant community composition in aquatic ecosystems as well. AM colonization benefits wetland vegetation increasing productivity and helping to ameliorate the effects of environmental and anthropogenic stresses. Given that TCS is a recognized antifungal agent, we examined whether TCS limits AM fungal growth resulting in reduced AM colonization in three wetland plants: Eclipta prostrata, Hibiscus laevis, and Sesbania herbacea. Seeds of three plant species collected from the wetlands in North Texas were germinated in growth room conditions on filter papers in petri dishes. Seedlings were inoculated with ~200 Glomus intraradices AM spores during transplantation to exposure trays. Plants were exposed to 0 ppbTCS (control), 0.4 ppb TCS (a concentration typical in a wastewater receiving stream), and 4 ppb TCS (an elevated concentration typical of an agricultural area receiving biosolids and/or effluent) in a flow-through system with supplement of 1/64th Long Ashton nutrient solution at the rate of 2.5ml/minute under green house conditions. Plants were harvested at days 10, 20,and 30 for evaluation of roots for AM colonization. AM propagules (hyphae, arbuscles, and vesicles) were quantified under 200X magnification. Two-way ANOVA showed significant (p<0.05) reduction of hyphal and arbuscular colonization in all three plant species treated with 0.4 ppb and 4 ppb TCS compared to controls. Vesicles were not affected by exposure; however, levels were consistently low in all TCS treatments. Further studies will be required to understand the mechanism of this TCS inhibition of mycorrhizal colonization in wetland plant species as well as the potential ecological consequences that a decline in the benefits of this symbiotic relationship may represent.
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1 - University of North Texas, Biology, 2434 Louise St, 17, Denton, Texas, 76201, USA
2 - University of North Texas, Biology, 1155 Union Circle , 305220, Denton, Texas, 76203 , United States
3 - Wilfrid Laurier University, Biology, 75 University Avenue West , Waterloo, Ontario, N2L 3C5, CA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 9th, 2012
Time: 1:45 PM