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No description available.

No description available.

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Six plant species were screened to determine potential suitability for phytoremediation of nitroglycerin (NG), a component in smokeless powders (SP). Seeds of Zea mays (corn), Triticum aestivum (wheat), Medicago sativa (alfalfa), Poa pratensis (Kentucky bluegrass), Trifolium pratense (red clover), and Phaseolus vulgaris (common bean) were sown into greenhouse mesocosms containing commercially prepared soil spiked with 0, 1, and 5% SP (w/w). Soil samples were collected 7, 60, and 90 days after seeding, extracted with ethanol, and analyzed for NG using a gas chromatograph with an electron capture detector. Plant growth observations were recorded using a simple scoring metric at 7, 14, 30, and 60 days after seeding. Soil nitrate and ammonium, potential by-products of NG decomposition, were quantified 90 days after seeding. NG disappearance in plant treatments was markedly, although not significantly (p > 0.05), higher than control at 1% SP, with legumes being the most successful treatment. Nitrate concentrations were significantly (p < 0.05) higher in legume than grass treatments. Soil ammonium was not correlated to any plant or SP treatment. Plant uptake of NG was minimal, suggesting a soil microbial effect in NG disappearance. More extensive screening studies are needed to determine which plants are the most successful remediators of NG. / Department of Natural Resources and Environmental Management

Seeds of many grasses and legumes from the Canadian Prairies have dormancy which prevents the germination of viable seeds in otherwise favorable conditions. Plant-derived smoke can improve germination in dormant seeds. Seeds of eight grasses, two legumes, and Lactuca sativa were investigated for the effects of seed priming in aqueous smoke solutions on germination, seedling emergence, seedling growth, and standing crop. Aqueous smoke solutions were produced by bubbling smoke generated from the incomplete combustion of wheat straw (Triticum aestivum cv. Unity) or prairie hay (Festuca hallii) through distilled water. Seeds were primed for 24 h in darkness using serial dilutions (1/1000v/v, 1/100v/v, 1/10v/v and 1/1v/v) of the aqueous smoke solutions. After priming, seeds were dried at 20°C in darkness for 7d and placed in petri dishes containing filter paper, after which 5 mL of distilled water were applied. Seeds were incubated at 10/0°C or 25/15°C in 12h light/12h darkness or 24 h darkness for 49 d. Seeds were also primed using 1/100v/v aqueous smoke solutions of wheat straw or prairie hay and seeded in the field. Non-primed seeds and those primed in distilled water (0/1v/v) were used as controls. Within species, germination varied significantly (P≤0.05) among concentrations of aqueous solutions of smoke, smoke type, light, temperature, and their interactions. Total germination of Astragalus cicer, Trifolium ambiguum, Hesperostipa comata, Stipa viridula, and Pascopyrum smithii was not changed by priming seeds. Depending on light or temperature treatments, priming seeds of Agropyron dasystachyum, Elymus junceus, Dactylis glomerata, Elymus angustus, and Festuca hallii in aqueous smoke solutions improved germination by 16%, 20%, 32%, 49%, and 50%, respectively. Priming seeds in aqueous smoke solutions reduced the number of days to 50% germination for Trifolium ambiguum, Lactuca sativa, Festuca hallii, and Stipa viridula (2 d), Elymus junceus (3 d), Dactylis glomerata (4 d), Hesperostipa comata (10 d), and Pascopyrum smithii (15 d). Priming seeds in aqueous smoke solutions increased seedling lengths (combined hypocotyl and radicle lengths) for Elymus angustus and Hesperostipa comata by 28% and 100%, respectively, but it reduced seedling lengths of Lactuca sativa, Festuca hallii, and Trifolium ambiguum. Seedlings from seeds primed in aqueous smoke solutions generated from wheat straw were longer for Lactuca sativa (83%), Elymus angustus (52%), and Hesperostipa comata (36%) as compared with prairie hay, respectively. Priming seeds interacted with smoke type to increase seedling lengths for Pascopyrum smithii (92%), Elymus junceus (100%), and Agropyron dasystachyum (100%), but it reduced seedling lengths for Astralagus cicer (26%), Trifolium ambiguum (55%), and Dactylis glomerata (90%). Exposing seeds to aqueous smoke solutions partially substituted a light requirement for germination in Pascopyrum smithii, Festuca hallii, Hesperostipa comata, Dactylis glomerata, Agropyron dasystachyum, Stipa viridula, and Elymus junceus. Priming seeds in aqueous smoke solutions increased standing crop of Dactylis glomerata by 57%, but total seedling emergence and rate of emergence of seedlings in the field were not different (P>0.05) among priming treatments. Priming seeds in aqueous smoke solutions generated from wheat straw or prairie hay can stimulate germination in Agropyron dasystachyum, Dactylis glomerata, Elymus junceus, Elymus angustus, and, Festuca hallii.

The growth and development of various meadow species was monitored while growing under enhanced UV-radiation in the natural light environment. Growth responses to supplementary ultraviolet-B (UV-B+A) were mostly inhibitory when compared to the ambient daylight treatment for Bellis perennis, Cardamine pratensis, Cynosurus critatus and Ranunculus ficaria. When the response of ultraviolet-A (UVA) treated plants were compared with those of the UV-B+A, differences were found which varied according to the species and parameter investigated. No correlation in B. perennis growth responses could be made with reallocation of carbohydrates or with photosynthesis. The stomata of B. perennis grown under enhanced UV-B+A were less capable of closing than those of the ambient plants. Increases in the concentration of UV-absorbing compounds were found in the UV radiation treatment when dry weight accumulation was inhibited in C. pratensis. To further understand the growth responses of the UV-A treatment and their relationship to the UV-B responses, polychromatic action spectra in the natural environment were employed. B. perennis had an action maximum in the UV-B (280-315 nm), while C. cristatus demonstrates no action in the UV-B but action in the UV-A region (315-400 nm). Dry weight accumulation was found to respond differently to UV treatments when investigating Arabidopsis thaliana ecotypes. UV-B+A treatment was found to inhibit dry weight accumulation in most ecotypes. When UV-B+A induced inhibition was expressed in terms of ambient growth rate for each ecotype, a linear relationship could be derived. The higher the growth rate the more susceptible the ecotype was to UV-B+A inhibition. The pertinence of the UV-A treatment and UV protocol is discussed. It is suggested that UV responses could alter the diversity of the meadow equilibrium and these effects could be exacerbated by water loss.

No description available.

Frequent rearrangements, typically through homologous recombination in plant mitochondrial genomes often result in different upstream and downstream sequences for the same gene among a number of species. Transcription and RNA processing signals are therefore different, even among closely related plants. To evaluate the impact of DNA rearrangements on gene expression I conducted a comparative analysis of the S7 ribosomal protein gene (rps7) among a number of grasses: wheat, rice, maize, barley, rye, brome, Lolium and oats (grasses whose evolutionary divergence times range from about 5 to 60 Mya). Using circularized-RT-PCR to simultaneously map rps7 transcript termini I found that 3’ends for various RNA species are homogeneous, mapping to conserved sequences among plants. 5’ termini are more complex and can be both discrete and heterogeneous for different transcripts, both within and among plants. Genome rearrangements upstream of the rps7 start codon for some but not all species has led to plant-specific signals for both rps7 transcription and RNA processing. Termini for rps7 precursor species in wheat and Lolium are very discrete and likely use different upstream tRNAs as processing signals for end-cleavage. A number of potential stem-loop structures have also been identified at or near 5’ and 3’ termini which may function in maturation of transcript ends or provide transcript stability and protection from degradation by ribonucleases. C-to-U RNA editing of non-coding sequences, a rare event, was observed at multiple sites within the 5’ and 3’UTRs among plants. Some sites may even be developmentally regulated as CR-RT-PCR experiments were conducted using mitochondrial RNA isolated from seedlings and germinating embryos. Taken together, my observations demonstrate the frequency of upstream DNA rearrangements and the variety of signals used for expression of rps7 among grasses, providing new insights into the complexities of mRNA production in plant mitochondria.