Ecophysiology of weedy species

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The long-term goal of my research program is to improve our understanding of the ecophysiology of weedy species, particularly of the factors affecting their size hierarchy and allometry, their inter- and intra-species interactions, and their interactions with biotic (e.g. plants and insects) and abiotic (e.g. UV-B radiation level and soil moisture stress) environments. Specific objectives of the proposed research are to determine: 1. if R/FR ratio modifies the size hierarchy and allometry of the agricultural weeds Amaranthus retroflexus, Chenopodium album, Setaria viridis, and Avena fatua and if these species differ in this regard, 2. how environmental stressors (UV-B radiation level and soil moisture stress) and nitrogen fertilization influence the optical properties (transmission, reflectance, and absorption) of leaves of these weeds with regard to FR light and if there are any interactions between these effects and weed species, leaf age or leaf position on the stem, 3. if reduction of leaf anthocyanin content in response to low R/FR alters the susceptibility of plants to an elevated UV-B radiation level, and 4. if soil moisture stress alters the allelopathic influence of Cynoglossum officinale leaves on the migratory grasshopper M. sanguinipes by altering their pyrrolizidine alkaloid content. Since size hierarchy influences plant-plant interactions, contribution of propagules by the individuals of a population to the next generation and biodiversity, an understanding of the effect of R/FR ratio on population size structure is needed. A difference in the allometric response of these weeds to R/FR ratio would have significant implications for their interaction with neighbours. Knowledge of the effect of UV-B radiation level, soil moisture stress and nitrogen fertilization on leaf optical properties and of any interactions between these effects and weed species, leaf age or leaf position on the stem would have significant implications for their potential to exert a shade-avoidance response. The research will also show if soil moisture stress influences the allelopathic interaction between C. officinale and the migratory grasshopper M. sanguinipes.