AUTHOR=Fernandez Catherine , Monnier Yogan , Santonja Mathieu , Gallet Christiane , Weston Leslie A. , Prévosto Bernard , Saunier Amélie , Baldy Virginie , Bousquet-Mélou Anne 

TITLE=The Impact of Competition and Allelopathy on the Trade-Off between Plant Defense and Growth in Two Contrasting Tree Species

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00594

DOI=10.3389/fpls.2016.00594

ISSN=1664-462X

ABSTRACT=<p>In contrast to plant-animal interactions, the conceptual framework regarding the impact of secondary metabolites in mediating plant-plant interference is currently less well defined. Here, we address hypotheses about the role of chemically-mediated plant-plant interference (i.e., allelopathy) as a driver of Mediterranean forest dynamics. Growth and defense abilities of a pioneer (<italic>Pinus halepensis</italic>) and a late-successional (<italic>Quercus pubescens</italic>) Mediterranean forest species were evaluated under three different plant interference conditions: (i) allelopathy simulated by application of aqueous needle extracts of <italic>Pinus</italic>, (ii) resource competition created by the physical presence of a neighboring species (<italic>Pinus</italic> or <italic>Quercus</italic>), and (iii) a combination of both allelopathy and competition. After 24 months of experimentation in simulated field conditions, <italic>Quercus</italic> was more affected by plant interference treatments than was <italic>Pinus</italic>, and a hierarchical response to biotic interference (allelopathy &lt; competition &lt; allelopathy + competition) was observed in terms of relative impact on growth and plant defense. Both species modulated their respective metabolic profiles according to plant interference treatment and thus their inherent chemical defense status, resulting in a physiological trade-off between plant growth and production of defense metabolites. For <italic>Quercus</italic>, an increase in secondary metabolite production and a decrease in plant growth were observed in all treatments. In contrast, this trade-off in <italic>Pinus</italic> was only observed in competition and allelopathy + competition treatments. Although <italic>Pinus</italic> and <italic>Quercus</italic> expressed differential responses when subjected to a single interference condition, either allelopathy or competition, species responses were similar or positively correlated when strong interference conditions (allelopathy + competition) were imposed.</p>