Plant neighbor identity influences plant biochemistry and physiology related to defense.
BACKGROUND
Chemical and biological processes dictate an individual organism's ability to recognize and respond to other organisms. A small but growing body of evidence suggests that plants may be capable of recognizing and responding to neighboring plants in a species specific fashion. Here we tested whether or not individuals of the invasive exotic weed, Centaurea maculosa, would modulate their defensive strategy in response to different plant neighbors.


RESULTS
In the greenhouse, C. maculosa individuals were paired with either conspecific (C. maculosa) or heterospecific (Festuca idahoensis) plant neighbors and elicited with the plant defense signaling molecule methyl jasmonate to mimic insect herbivory. We found that elicited C. maculosa plants grown with conspecific neighbors exhibited increased levels of total phenolics, whereas those grown with heterospecific neighbors allocated more resources towards growth. To further investigate these results in the field, we conducted a metabolomics analysis to explore chemical differences between individuals of C. maculosa growing in naturally occurring conspecific and heterospecific field stands. Similar to the greenhouse results, C. maculosa individuals accumulated higher levels of defense-related secondary metabolites and lower levels of primary metabolites when growing in conspecific versus heterospecific field stands. Leaf herbivory was similar in both stand types; however, a separate field study positively correlated specialist herbivore load with higher densities of C. maculosa conspecifics.


CONCLUSIONS
Our results suggest that an individual C. maculosa plant can change its defensive strategy based on the identity of its plant neighbors. This is likely to have important consequences for individual and community success.
Broz
Amanda K
AK
Department of Horticulture and Landscape Architecture and Center for Rhizosphere Biology, Colorado State University, Fort Collins, CO 80523, USA.
Broeckling
Corey D
CD
De-la-Peña
Clelia
C
Lewis
Matthew R
MR
Greene
Erick
E
Callaway
Ragan M
RM
Sumner
Lloyd W
LW
Vivanco
Jorge M
JM
D000085:Acetates / Q000494:pharmacology; D018533:Biomass; D031179:Centaurea / Q000737:chemistry* / Q000254:growth & development*; D003517:Cyclopentanes / Q000494:pharmacology; D017753:Ecosystem; D055442:Metabolome; D054883:Oxylipins / Q000494:pharmacology; D010636:Phenols / Q000737:chemistry*; D013312:Stress, Physiological
D000085:Acetates; D003517:Cyclopentanes; D054883:Oxylipins; D010636:Phenols; C072239:methyl jasmonate