Abstract
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 (Pinus halepensis) and a late-successional (Quercus pubescens) Mediterranean forest species were evaluated under three different plant interference conditions: (i) allelopathy simulated by application of aqueous needle extracts of Pinus, (ii) resource competition created by the physical presence of a neighboring species (Pinus or Quercus), and (iii) a combination of both allelopathy and competition. After 24 months of experimentation in simulated field conditions, Quercus was more affected by plant interference treatments than was Pinus, and a hierarchical response to biotic interference (allelopathy < competition < 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 Quercus, an increase in secondary metabolite production and a decrease in plant growth were observed in all treatments. In contrast, this trade-off in Pinus was only observed in competition and allelopathy + competition treatments. Although Pinus and Quercus 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.
Highlights
Interference between plants typically refers to either competition for resources or chemically-mediated interference (Reigosa et al, 1999; Schenk, 2006; San Emeterio et al, 2007)
Our findings demonstrated that plants may initiate a defensive response through chemical detection of neighbors in the absence of physical cues, similar to those well-described findings for animal-defensive behavior (Callaway, 2002) or against abiotic stress (Ormeño et al, 2007b)
Results reported for the two Mediterranean tree species, Pinus halepensis and Quercus pubescens, strongly suggest the existence of differential effects of various biotic interference mechanisms on sapling development, and the need to consider their cumulative or antagonistic effects in plant community dynamics (Viard-Crétat et al, 2012)
Summary
Interference between plants typically refers to either competition for resources (e.g., nutrients, light, water) or chemically-mediated interference (i.e., allelopathy) (Reigosa et al, 1999; Schenk, 2006; San Emeterio et al, 2007). Recent research has shown that allelopathy can affect the patterning of plant communities (Callaway and Ridenour, 2004; Fernandez et al, 2013) In this process, phytochemicals released into the environment inhibited the germination and growth of neighboring plants by altering their metabolism or impacting their soil community mutualists. Phytochemicals released into the environment inhibited the germination and growth of neighboring plants by altering their metabolism or impacting their soil community mutualists Most of these studies have focused on plant invasion and the Novel Weapons Hypothesis (NWH). A limited conceptual framework exists for the role of plant chemicals in the natural dynamics of co-evolved native species (Inderjit et al, 2011; Meiners, 2014), but it has been suggested that allelopathic interference may prove to be as important as competition for resources in modulating plant community function and dynamics. It is crucial to evaluate the relative importance of these two plant interference mechanisms [resource competition (C) and allelopathy (A)] in experimentation, even if it is difficult and often unrealistic to separate these interactions in complex ecosystems
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
