DISSERTATION RESEARCH: Mechanisms of Anoxia Tolerance in Marsh Grasses in the Genus Spartddina (Poaceae)

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AbstractAll higher plants depend on oxygen for cellular respiration. Under waterlogged conditions, oxygen is displaced from soil and usually is not sufficient to support aerobic respiration. Therefore, it is in the interest of wetland plants to lower aerobic demand and provide oxygen to submerged tissues. Many wetland plants have been shown to transport atmospheric oxygen internally to support respiration in submerged tissues. However, oxygen transport rates have not previously been compared between species of different flooding tolerances. Additional physiological factors, especially aerobic respiration rates and sulfide sensitivity, may also account for differences in flood tolerance but have not been investigated in wetland plants. Work is proposed to investigate the physiological basis of anoxia tolerance in a group of saltmarsh plants. Spartina is a small genus (about 15 species) in the grass family that grows in a wide range of habitats, including low intertidal marsh, high intertidal marsh, and freshwater areas. A comprehensive survey will be performed on the genus to elucidate the physiological mechanisms conferring success in anoxic low intertidal areas. In the proposed research, rates of internal oxygen transport will be measured and compared across Spartina species. Respiration rates will also be measured, along with aerobic and anaerobic respiration enzyme activities, and sulfide sensitivity across species. Knowledge of the relevant anoxia tolerance mechanisms may help understand the ecology of a dominant member of saltmarsh communities. The work is expected to help correctly identify mechanisms of flooding tolerance and estuarine zonation as well as provide a clear characterization of high intertidal and low intertidal estuarine functional types. This knowledge may later become useful in managing plants subjected to waterlogging conditions or to genetically engineer more flooding-tolerant crops.