Thesis (M. Env. St.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1993. / Includes bibliographical references (leaves [34-40]).

Anoxia tolerance of Acorus calamus, Iris pseudacorus and Vaccinium macrocarpon has been investigated by incubating whole plants under anaerobic conditions in the dark. Long-term survival of rhizomes under anoxia has been described in previous studies, but this study has shown that green leaves can also endure anoxia for prolonged periods. Leaves of A. calamus, I.pseudacorus and V.macrocarpon remained green and turgid under anoxia for up to 75d, 60d and 45d respectively. All growth processes ceased in leaves under anoxia. Anaerobic energy production via ethanol fermentation was active in all investigated plant organs as shown by the accumulation of ethanol. Low rates of anaerobic CO2 production indicated however, that the overall metabolic activity in the leaves was low under prolonged anoxia. The leaves seemed to adapt to the anaerobic conditions by an overall reduction of energy consumption rather than acceleration of the glycolytic rate. The demands for fermentable substrate were met by the mobilisation of internal carbohydrate reserves in leaves of V.macrocarpon. A.calamus and I.pseudacorus leaves contained only small amounts of carbohydrates, and these leaves possibly received carbohydrates from the stores in the rhizome. Prolonged anoxia considerably affected the leaf capacity for respiration and photosynthesis. After 28d of anoxia, respiratory capacity was reduced in A.calamus and V.macrocarpon by 80%, and in I.pseudacorus by 90-95%; this corresponded with a decline in the activity of the cytochrome c oxidase. The photosynthetic capacity of leaves was decreased after 28d of anoxia by 83% in A.calamus, by 97% in I.pseudacorus and by 80% in V.macrocarpon. The reduction in the photosynthetic capacity was accompanied by alterations in the chlorophyll fluorescence pattern indicating damage to the PSII reaction centre and the subsequent electron transport; only minor changes occurred in the chlorophyll content of anaerobic leaves. On return to air and light, recovery of respiration and photosynthesis occurred in the leaves, but species-specific differences were observed in the speed of recovery. Among the three investigated species, A.calamus leaves endured the anoxic conditions longer than leaves of the other two species; and on return to air, A.calamus leaves showed the most rapid recovery. A.calamus was characterised by efficient carbohydrate utilisation under anoxia. Cellular membranes and organelle ultrastructure appeared to be stable in A.calamus leaves for at least 28d of anoxia.

The relative iron (II) tolerance of a range of wetland plants was determined and compared with some species characteristic of well drained soils. A wide range of tolerance occurred amongst the wetland species but they were generally more tolerant than those from well drained soils. No correlation was found between iron (II) tolerance and the amount of air space {% v/v) (aerenchyma) in the roots of these species. There was a significant negative correlation between air space and iron uptake by roots. This may have been caused by iron (II) oxidation in the rhizosphere resulting in decreased availability. There was evidence that differential iron (II) tolerance of excised root tips was maintained under aerobic and anaerobic conditions. It was thus suggested that iron (II) tolerance may not be dependent on iron exclusion or oxidation of iron (II) by oxygen diffusing through the aerenchyma. Levels of malic and citric acids in roots were altered by iron (II) sulphate, but the absolute levels and changes in levels had no correlation with the iron (II) tolerance, of the species. Peroxidase and catalase activities in root tips of plants gown in drained and flooded sand culture were measured and considered in relation to the oxidising power of roots. Activity was detected in all species examined but was generally I unaffected by flooding. Evidence from the literature suggested that these enzymes of peroxide metabolism are unlikely to be active in flooded roots and so could not mediate their oxidising power. The structure of root aerenchyma had great variability between species. The Cyperaceae had the most complex and well organised structure. Growth under flooded conditions increased air space in most species, but there were exceptions. In Eriophrum angustifolium and E. vaginatum air space was high under drained conditions and was not increased by flooding. In Filipendula ulmaria the small amount of air space was not increased by flooding. Low nutrient levels increased air space production in Nardus stricta. The function of aerenchyma and the influence of environmental factors on its production are discussed.

The flooding and anoxia tolerance of three barley cultivars (Hordeum vulgare L. cv. Kustaa, Hankki ja-673 and Pokko), beaked sedge (Carex rostrata Stokes), rice (Oryza sativa L. cv. FR13A) and yellow flag (Iris pseudacorus L.) have been assessed by determining the length of anoxia tolerance and the productivity of the barley cultivars under flooding. Other physiological parameters related to flooding and anoxia tolerance were also determined, and they included alcohol dehydrogenase activity and its enzyme kinetic parameters KM and Vmax (for reaction acetaldehyde to ethanol) in the barley cultivars and beaked sedge, production of ethanol, CO2 and some organic acids in seedlings of the barley cultivars under anoxia, and superoxide dismutase activity in barley, rice and yellow flag under hypoxia and anoxia. A study of the root anatomy of barley and beaked sedge was also conducted. The anoxia tolerance experiments revealed differences in the three barley cultivars and the flooding tolerance experiment gave very similar results. Thus, Kustaa proved to be the most anoxia tolerant and most productive under flooding, Hankki ja-673 being intermediate and Pokko the least anoxia tolerant and the least productive during flooded conditions. Simultaneous measurements of ethanol, carbon dioxide and organic acid production during anoxia together with determination of dry weight loss during the period of oxygen deprivation showed that the rate of ethanolic fermentation was significantly faster in the more intolerant cultivars. Also, the more anoxia intolerant cultivars lost more of their dry weight during the anoxic incubation than the most tolerant cultivar. These results were in agreement with the metabolic theory of flooding tolerance. Superoxide dismutase activity measurements in the barley cultivars as well as in rice under hypoxia did not reveal any changes in the activity with the onset of oxygen deprivation. Neither did incubation under total anoxia increase SOD activity. In yellow flag rhizomes, which are very flood and anoxia tolerant, large increases in SOD activity took place during and after oxygen deprivation indicating greater protection against subsequent oxidative damage. Injuries of this nature have been noticed earlier in flood intolerant species. The anatomical study of the roots and rhizomes of beaked sedge and roots of barley cultivars revealed the larger percentage of aerenchyma in beaked sedge.

Thesis (M.Sc.)--College of William and Mary. / Includes bibliographical references.

Thesis (M. Env. Sc.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1999. / Includes bibliographical references (leaves 104-110).

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on August 4, 2009). Includes bibliographical references (p. 89-92).

The Prairie Pothole Region, specifically eastern North Dakota, has experienced intense disturbance from agricultural demands and urban sprawl. This study assessed wetlands across the rural, peri-urban, and urban gradient to determine the impacts of urbanization on water quality and vegetation composition. Thirty wetlands were randomly selected and compared based on land use type and the impervious to pervious surface ratio within one mile of each wetland. Water quality samples were taken in 2015 and 2016, and a vegetation assessment was completed at all wetlands. Results indicate disturbance from urbanization impacts wetland water quality and vegetation composition. Rural wetland water quality and vegetation significantly differ from both peri-urban and urban wetlands, whereas peri-urban and urban wetland water quality and vegetation do not differ. Information from this study is useful to wetland professionals across the globe as urban development and sprawl continue to impact wetlands.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science, 2017 / Six different plant species that grow in a natural wetland impacted by old gold mining and other industrial activities were randomly selected with surface sediments. These included: Cyperus eragrostis (Nutgrass), Datura stramonium (Jimson weed), Melilotus alba (White sweetclover), Panicum coloratum (Blue panicgrass), Persicaria lapathifolia (Pale smartweed) and Phragmites australis (Common reed). These were used to investigate the levels of mercury in the wet and dry seasons, as well as to evaluate which of the species could be utilized for the remediation of mercury contaminated areas. The results obtained indicated that metal contamination could be determined from sediments and plant tissues. The pH values of the sediment samples were mostly neutral to slightly acidic and the redox potential was high in the wet season. On the other hand the dry season was characterised by very acidic and moderately oxidizing conditions. In summer all six plant species had higher concentration of HgT in sediments, whereas in winter the levels of HgT were elevated in the aerial tissues of the plants. The mercury accumulation patterns differed according to individual plant species and seasonality. Seasonal differences were significant but generally the MeHg concentrations in the wet season were higher in both surface sediments and plant tissues. Mercury methylation differed between species but concentration of MeHg was in general higher in plants with high concentration of mercury in sediments. The conversion of bioavailable HgT seemed more pronounced in tissues of the plants sampled in the wet season unlike those sampled in the dry season. Generally bioaccumulation factors were less than 1 in both the wet and dry seasons for all the plant species indicating that Hg was mainly retained in sediments. The translocation factor values were greater than 1 meaning metals were accumulated fundamentally in aboveground tissues for the plants D. stramonium, P. lapathifolia, P. coloratum and C. eragrostis in both the wet and dry seasons. The small bioaccumulation factors combined with translocation factor values greater than 1 were an indication that mercury present in the sediments was not the only source of mercury for the plant species growing in a contaminated environment. For P. australis the translocation of mercury was heavily influenced by seasonality, however this was not the case with M. alba. All the selected plant species demonstrated the capacity to grow in a heavily contaminated area, where P. australis and M. alba seemed to have developed an exclusion strategy to deal with toxic heavy metals therefore suitable for phytostabilisation. D. stramonium, P. lapathifolia, P. coloratum and C. eragrostis on the other hand exhibited characteristics of plants that can be successfully used for phytoextraction and phytovolatilization. / XL2018

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 103-112).