Mycorrhizal colonization does not affect tolerance to defoliation of an annual herb in different light availability and soil fertility treatments but increases flower size in light-rich environments
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Heterogeneous distribution of resources in most plant populations results in a mosaic of plant physiological responses tending to maximize plant fitness. This includes plant responses to trophic interactions such as herbivory and mycorrhizal symbiosis which are concurrent in most plants. We explored fitness costs of 50% manual defoliation and mycorrhizal inoculation in Datura stramonium at different light availability and soil fertility environments in a greenhouse experiment. Overall, we showed that non-inoculated and mycorrhiza-inoculated plants did not suffer from 50% manual defoliation in all the tested combinations of light availability and soil fertility treatments, while soil nutrients and light availability predominately affected plant responses to the mycorrhizal inoculation. Fifty percent defoliation had a direct negative effect on reproductive traits whereas mycorrhiza-inoculated plants produced larger flowers than non-inoculated plants when light was not a limiting factor. Although D. stramonium is a facultative selfing species, other investigations had shown clear advantages of cross-pollination in this species; therefore, the effects of mycorrhizal inoculation on flower size observed in this study open new lines of inquiry for our understanding of plant responses to trophic interactions. Also in this study, we detected shifts in the limiting resources affecting plant responses to trophic interactions.
KeywordsCross-pollination Floral display Seed set Solanaceae Trophic interactions
We thank Antonio Castillo for all the logistic support in setting up the greenhouses, Reyna Hernández for assistance throughout the experiment, Mimi Vega-Fruits and Armando Aguirre for their help at harvest and Ing. Francisco J. Guzmán (Centro de Conservación y Educación Ambiental Francisco Javier Clavijero) for all his logistical support, and two anonymous reviewers for their constructive comments on early drafts of this study. Funding was provided by CONACYT, (scholarship 190667 awarded to A.ACh) and the Red de Biología Evolutiva INECOL. The reported experiment complied with the current legislation on environmental health of Mexico.
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