Effects of ( + /-)-Catechin in Vitro , in Soil , and in the Field Inderjit

Background: Exploring the residence time of allelochemicals released by plants into different soils, episodic exposure of plants to allelochemicals, and the effects of allelochemicals in the field has the potential to improve our understanding of interactions among plants. Methodology/Principal Findings: We conducted experiments in India and the USA to understand the dynamics of soil concentrations and phytotoxicity of (6)-catechin, an allelopathic compound exuded from the roots of Centaurea maculosa, to other plants in vitro and in soil. Experiments with single and pulsed applications into soil were conducted in the field. Experimental application of (6)-catechin to soils always resulted in concentrations that were far lower than the amounts added but within the range of reported natural soil concentrations. Pulses replenished (6)-catechin levels in soils, but consistently at concentrations much lower than were applied, and even pulsed concentrations declined rapidly. Different natural soils varied substantially in the retention of (6)-catechin after application but consistent rapid decreases in concentrations over time suggested that applied experimental concentrations may overestimate concentrations necessary for phytotoxicity by over an order of magnitude. (6)-Catechin was not phytotoxic to Bambusa arundinacea in natural Indian soil in a single pulse, but soil concentrations at the time of planting seeds were either undetectable or very low. However, a single dose of (6)-catechin suppressed the growth of bamboo in sand, in soil mixed with organic matter, and Koeleria macrantha in soils from Montana and Romania, and in field applications at 40 mg l. Multiple pulses of (6)-catechin were inhibitory at very low concentrations in Indian soil. Conclusions/Significance: Our results demonstrate that (6)-catechin is highly dynamic in natural soils, but is phytotoxic well below natural concentrations measured in some soils and applied at low concentrations in the field. However, there is substantial conditionality in the effects of the allelochemical. Citation: Inderjit, Pollock JL, Callaway RM, Holben W (2008) Phytotoxic Effects of (6)-Catechin In vitro, in Soil, and in the Field. PLoS ONE 3(7): e2536. doi:10.1371/ journal.pone. 0002536 Editor: Michael Somers, University of Pretoria, South Africa Received February 24, 2008; Accepted May 19, 2008; Published July 2, 2008 Copyright: 2008 Inderjit et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by the University of Delhi, India; Ministry of Environment and Forests, India; Research Office at The University of Montana, the Aldo Leopold Wilderness Center, the USFS Fire Sciences Laboratory and Rocky Mountain Research Station, the USDA, DoD SERDP, the National Science Foundation, and the Civilian Research and Development Foundation. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: inderjit@cemde.du. ac.in