Life Sciences Commons^™

Carbon And Nitrogen Dynamics In Plants Grown At Low Co2 Conditions Of The Past, Andre Galvao Duarte

Electronic Thesis and Dissertation Repository

For most of the recent evolutionary history of plants, atmospheric CO₂ concentrations have been far below modern values. However, little is known about how plants grown in a low CO₂ environment balance their carbon demand for growth while meeting their requirement for nitrogen acquisition, the establishment of mycorrhizal fungal associations, and the production of defense compounds. Here, I investigated how low CO₂ affects Elymus canadensis and Picea mariana by comparing their growth at low and current CO₂ concentrations. I found that reduced N availability exacerbated low CO₂ effects on growth, and reduced stomatal index and …

Evolutionary History Of The Angiosperm Npf1 Gene Subfamily: Duplications, Retention And Functional Implications For Root Symbioses And Development, Giovanna Sassi

Graduate College Dissertations and Theses

ABSTRACT

The success of land plants can be attributed to the evolution of beneficial associations between plant roots and soil microbes. Root-microbe mutualisms extend the range of plant nutrient acquisition delivered through the hyphal network of mycorrhiza, an ancient and widespread plant symbiosis, or by the more recent adaptive innovation of nitrogen-fixing nodule symbioses. A plant’s genetic toolkit governs its selection of beneficial symbionts and the developmental extent of these intimate interactions. However, the evolutionary origins and function for only a few symbiotic signaling components have been explored. The central aim of this dissertation is to resolve the evolutionary events …

Stoichiometric Homeostasis In Two Native And Two Invasive South Dakotan Grasses, Joshua Thonas Harvey

Electronic Theses and Dissertations

Increased nutrient availability has been widely linked to the success of invasive plants, however a general mechanism explaining these observations is lacking. Stoichiometric homeostasis (H), which is the regulation of internal nutrient concentrations, has been used to explain changes in plant community diversity under alterations in nutrient availability. One hypothesis holds that plants with high regulation (larger H) decrease in abundance in nutrient enriched conditions but are stable in nutrient deficient and drought conditions, likely due to extensive root systems. Additionally, plants with low regulation (lower H) increase in abundance under nutrient enriched conditions but are sensitive to drought …