Since plants cannot actively avoid herbivory, they rely on two primary strategies to maintain their fitness in the face of herbivore pressure: resistanceâ€”the deterrence of herbivory via physical and chemical meansâ€”and toleranceâ€”recuperation of aboveground mass after herbivory. Although diverse groups have been shown to be tolerant to herbivory, mechanisms of tolerance are not yet well known. There is also very little known about the ecological relevance of tolerance strategies in wild populations. In Arabidopsis thaliana, the apical meristem suppresses growth of axillary meristems to a high degree under normal conditions, but a number of axillary meristemswill grow after apical meristem damage (AMD). Intraspecific variation in tolerance ranges from decreased fitness after herbivory (undercompensation) to increased fitness after herbivory (overcompensation). In the model organism Arabidopsis thaliana,phenotypes from both ends of this spectrum have been observed in the laboratory, even among closely related strains. Fifteen populations of Arabidopsis thaliana were sampled from throughout its natural range. The percentage of plants with AMD was assessed in each population and phenotypic data was collected for all plants. Adjusted fruit number was used as a proxy of fitness and was calculated as the sum of fruits and the product of flowers and the percentage of non-aborted fruits observed in each population. Fitness was not significantly different in plants that experienced AMD and plants that did not. This implies that natural populations of Arabidopsis thaliana are highly tolerant. Additionally,I ran analyses of variance to determine the amount of variance in fitness caused by study site, AMD, and AMD x site. Only site was a significant contributor to variance in fitness. Additionally, I performed qPCR to determine the relationship in gene expression (if any) of four genes to Arabidopsis thaliana's response to AMD: AT1G6270.1,CYP72A11, JUMONJI14 and SUR1. All genes were shown to be expressed at significantly lower levels in plants that had received AMD relative to expression of the housekeeping gene 18S rRNA, which did not change significantly in expression between damaged and undamaged treatments. The implication of these findings will be discussed.
Date of publication
Dalrymple, Justin, "A Description of Tolerance to Apical Meristem Damage in Wild Populations of Arabidopsis thaliana and its Genetic Basis" (2014). Biology Theses. Paper 18.