Thesis (M.S.)--Montana State University--Bozeman, 2006. / Typescript. Chairperson, Graduate Committee: Wendy Stock. Includes bibliographical references (leaves 100-103).

Thesis (M.S. in natural resource sciences)--Washington State University, August 2006. / Includes bibliographical references (p. 42-45).

Thesis (M.Phil.) -- University of the Western Cape, 2005. / Includes bibliographical references (leaves 130-132).

Thesis (doctoral)--Lunds universitet, 1778. / At head of title: J.H.J.N. Reproduction of original from Kress Library of Business and Economics, Harvard University. Goldsmiths'-Kress no. 11689.2-2.

Thesis (Ph.D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 104-107). Also available on the Internet.

It is not clear whether flood-tolerant plants survive in waterlogged soils because they maintain aerobic activity in all regions of the roots, or whether biochemical adaptations to anoxia are involved. Many plants have some capacity for internal ventilation, and so in order to exclude oxygen from the root environment it is necessary to subject both the roots and the shoots to anoxia. Pea and rice seedlings were exposed to anoxia for 1 to 24 h and their tolerances and survival compared. With pea and rice, cv. Oeiras, tolerance of anoxia decreased as the temperature increased, although rice was more tolerant than pea at a given temperature. Increasing amounts of K+ were lost from the roots of whole seedlings during anoxia, and seedling recovery on return to air was associated with the seedlings' ability to reabsorb most of the leaked K+. Aerobic respiration in the root tips was associated with both K+ uptake by pea seedlings, and the recovery and subsequent growth of pea and three varieties of rice after anoxia. All rice varieties were more tolerant of anoxia at 25°C than was pea at 20°C, but differences between the tolerance limits of the rice varieties were apparent. Although some pea and rice seedlings appeared undamaged after anoxia, the subsequent growth rates of pea and rice, cv. IR8, were seriously impaired. Ethanol accumulated around the roots of all seedlings during anoxia, but there was no correlation between the quantity of ethanol produced and the different tolerance limits of the seedlings. Pea seedlings that were prevented from transpiring during anoxia were damaged earlier than controls, possibly because of an increase in the rate of accumulation of a toxic product of anaerobic metabolism in these seedlings. Two percent glucose merely delayed, and did not prevent, the onset of damage in whole pea seedlings during anoxia, nor did it enhance the subsequent growth of the seedlings. Under these conditions, the accumulation of endogenous ethanol to a toxic concentration was considered to have been the more likely cause of seedling death. From the results presented in this thesis and elsewhere, it is concluded that-the immediate cause of seedling death during anoxia is a shortage of substrate for glycolysis, and that the additional effect of ethanol accumulation in some species may reduce their subsequent rate of recovery.

Breeding and selection for salt tolerance has been limited because of the large heterogeneity of natural saline soils and the lack of efficient criteria for measuring salt tolerance. Regulation of salt balances in leaves is an important aspect of salt tolerance. This work analyses the relationship between leaf ion concentrations and salt tolerance with the aim of using these traits as indicators of salt tolerance. This is done both in solution culture (hydroponics) and field trials (sprinkler irrigation with saline water). Varieties were found to differ in the amounts of ions accumulated in their leaves. However, these differences did not relate directly with their level of salt tolerance. The lack of correlation was partly due to difficulties in estimating salt tolerance in the field. Also, the Triple Line Sprinkler system (TLS) used in the field experiments posed several problems, the most important ones being related to direct ion absorption by the leaves. The high concentrations of CaC12 (in addition to NaCl) used in the irrigation water added a further complication. In hydroponic experiments, a minimum of 2 mol in-' Ce' was enough to prevent an indiscriminate entry of Na' and to ameliorate the growth inhibition of plants growing at 200 mol in-' NaCl. Higher Caý' concentrations (50 mol in-' CaCl2) reduced even more the concentrations of Na' in leaves without significantly affecting growth. At these high levels of CaCl2 any toxic effect was probably caused by high Clconcentrations.

No description available.

>Magister Scientiae - MSc / In this study, the diversity of endophytic bacteria associated with food crops, sorghum (Sorghum bicolor L. Moench), pearl millet (Pennisetum glaucum L.) and groundnut (Arachis villosulicarpa) is investigated using culture-independent techniques: terminal retriction fragment length polymorphism (t- RFLP) and next generation sequencing (NGS). The first objective of this study was to investigate the effect of different DNA extraction protocols on mDNA yield and quality, as well as the diversity of endophytic bacteria retrieved from root and stem tissues (0.1g or 0.3g) of sorghum, pearl millet and groundnut. Protocols used include two classical methods (CTAB- and SDS-based) and five commercial kits: MoBio PowerPlant Pro® DNA Isolation Kit, Qiagen DNeasyR Plant Mini Kit, Fermentas GeneJET Plant Genomic DNA Purification Kit, MoBio PowerSoilTM DNA Purification Kit and MoBio UltraClean® Soil DNA Isolation Kit. Eletrophoresis and the Nanodrop were used to determine DNA yield and purity

An increasing cultural practice in soybean, Glycine max (L.), production is the use of winter annual cover crops before planting. Species of grasses, legumes, and forbs are planted for many agronomic purposes during the fall months. In the spring, cover crops are killed and soybean planted into the residue. When the termination of the cover crops is delayed for longer lasting benefits, insect pest issues can arise. The movement of insect pests from cover crops to subsequent cash crops happens through a connection known as the “Green Bridge”. Pests found in cover crops such as the pea leaf weevil, Sitona lineatus L. (Coleoptera: Curculionidae), can be particularly damaging to immature soybean plants. Experiments were conducted to tests how cover crops influence insect populations in soybean. Also, various chemical control options, soybean planting populations, and the timing of cover crop termination prior to planting were tested in these cover crop-soybean systems. Lastly, an experiment was conducted to measure how various species of cover crops and neonicotinoid seed treatments affect arthropod diversity in soybean fields.