Nan C. Vance

Phytoremediation of soil contaminated with low concentrations of radionuclides

Ecosystems throughout the world have been contaminated with radionuclides by above-ground nuclear testing, nuclear reactor accidents and nuclear power generation. Radioisotopes characteristic of nuclear fission, such as 137Cs and 90Sr, that are released into the environment can become more concentrated as they move up the food chain often becoming human health hazards. Natural environmental processes will redistribute long lived radionuclides that are released into the environment among soil, plants and wildlife. Numerous studies have shown that 137 Cs and 90Sr are not removed from the top 0.4 meters of soil even under high rainfall, and migration rate from the top few centimeters of soil is slow. The top 0.4 meters of the soil is where plant roots actively accumulate elements. Since plants are known to take up and accumulate 137 Cs and 90Sr removal of these radionuclides from contaminated soils by plants could provide a reliable and economical method of remediation. One approach is to use fast growing plants inoculated with mycorrhizal fungi combined with soil organic amendments to maximize the plant accumulation and removal of radionuclides from contaminated soils, followed by harvest of above-ground portion of the plants. High temperature combustion would be used to oxidize plant material concentrating 137 Cs and 90Sr, in ash for disposal. When areas of land have been contaminated with radionuclides are large, using energy intensive engineering solutions to remediate huge volumes of soil is not feasible or economical. Plants are proposed as a viable and cost effective method to remove radionuclides from the soils that have been contaminated by nuclear testing and nuclear reactor accidents.

SEASONAL AND TISSUE VARIATION IN TAXANE CONCENTRATIONS OF TAXUS BREVIFOLIA

Analysis of seven taxanes: taxol, baccatin III, 10-deacetyltaxol, 10-deacetylbaccatin III, 7-xylosyl-10-deacetyltaxol, cephalomannine and brevifoliol in extracts from bark and foliage of pacific yew (Taxus brevifolia) showed a gradient of decreasing concentration from stem base to branch tip. This decrease is attributed to the generally higher concentration of taxanes in the phloem tissue and the decrease in inner bark thickness from base to branch tip. Analysis of taxanes extracted from stem bark and needles sampled over a growing season showed that most taxane concentrations were significantly lower in the needles than in the bark. Typically, taxane concentrations in bark increased from May through August; whereas, in needles, concentrations changed little during that period. Two exceptions were baccatin III, which in the summer reached levels equivalent to bark, and brevifoliol which increased from March to August, reaching levels in needles nine times greater than bark.

Comparative Rates of Pollination and Fruit Set in Widely Separated Populations of a Rare Orchid (Cypripedium fasciculatum)

The rare orchid Cypripedium fasciculatum offers no reward to the small wasps that pollinate its flowers. Nonrewarding species typically suffer from low rates of pollination and fruit set, yet they appear frequently in the Orchidaceae. In order to understand the dynamics of pollination and fruit set in nonrewarding orchids and to evaluate whether a conservation strategy for C. fasciculatum should include managing for pollinator service, we evaluated factors influencing reproductive success in three widely separated populations. The percentage of open‐pollinated flowers maturing fruit varied greatly among populations, equaling 69% in Oregon, 29% in Idaho, and 18% in Colorado. These values are greater than is typical for a nonrewarding orchid. Thus, managing for pollinator service may be unnecessary, especially in the Oregon population. Like many nonrewarding orchids, the species appears to have a self‐compatible breeding system; fruit set did not differ between flowers receiving self pollen and flowers receiving cross pollen ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

POLLEN-PISTIL INTERACTIONS IN NORTH AMERICAN AND CHINESE CYPRIPEDIUM L. (ORCHIDACEAE)

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Taxol and cephalomannine concentrations in the foliage and bark of shade-grown and sun-exposed Taxus brevifolia trees

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Pollination and seed production in Xerophyllum tenax (Melanthiaceae) in the cascade range of central Oregon

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