Search Results - (Author, Cooperation:G. J. Taylor)

2012-12-12

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2012-12-12

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2015-11-14

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

1365-3040

Blackwell Publishing Journal Backfiles 1879-2005

Biology

We investigated the role that manganese superoxide dismutase (MnSOD, EC 1·15·1·1), an important enzyme of the antioxidant pathway, may play in aluminium (Al) toxicity/resistance. A wheat (Triticum aestivum) cDNA (WMnSOD) was cloned and up-regulation of the transcript was observed in root tips after 24 h exposure to 100 µm Al. The WMnSOD1 under the control of the CaMV35S promoter was expressed in canola (Brassica napus). Transgenic plants were phenotypically normal. Northern analyses showed enhanced levels of the WMnSOD1 and WMnSOD1-GUS transcripts and total SOD activity was 1·5- to 2·5-fold greater in transgenic plants than in wild type (WT) plants. Transgenic (T1) leaf discs showed increased retention of chlorophyll and reduced electrolyte leakage when exposed to methyl viologen (MV) as compared with WT leaf discs, suggesting that transgenic plants were more resistant to oxidative stress. When WT canola plants were exposed to aluminium (0–200 µm), inhibition of root growth, higher SOD activity and increased levels of malondialdehyde (MDA, an indicator of lipid peroxidation) were observed in roots. Aluminium-induced inhibition of root growth and accumulation of MDA was lower in homozygous transgenic plants (T2) compared with WT plants. Transgenic lines also showed lower synthesis of 1,3-β-glucans (callose, a sensitive marker for Al injury) as compared with WT. These data suggest that resistance to Al toxicity can be improved by overexpressing WMnSOD1.

Electronic Resource

1432-0819

lava flows ; xenoliths ; nodule beds ; levee deposits ; Hualalai Volcano, Hawaii

Springer Online Journal Archives 1860-2000

Geosciences

Abstract The basaltic Kaupulehu 1800–1801 lava flow of Hualalai Volcano, Hawaii contains abundant ultramafix xenoliths. Many of these xenoliths occur as bedded layers of semi-rounded nodules, each thinly coated with a veneer (typically 1 mm thick) of lava. The nodule beds are analogous to cobble deposits of fluvial sedimentary systems. Although several mechanisms have been proposed for the formation of the nodule beds, it was found that, at more than one locality, the nodule beds are overbank levee deposits. The geological occurrence of the nodules, certain diagnostic aspects of the flow morphology and consideration of the inferred emplacement process indicate that the Kaupulehu flow had an exceptionally low viscosity on eruption and that the flow of the lava stream was extremely rapid, with flow velocities of at least 10 m s-1 (more than 40 km h-1). This flow is the youngest on Hualalai Volcano and future eruptions of a similar type would pose considerable hazard to life as well as property.

Electronic Resource

1432-0819

Key words lava flows ; xenoliths ; nodule beds ; levee deposits ; Hualalai Volcano ; Hawaii

Springer Online Journal Archives 1860-2000

Geosciences

Abstract  The basaltic Kaupulehu 1800–1801 lava flow of Hualalai Volcano, Hawaii contains abundant ultramafic xenoliths. Many of these xenoliths occur as bedded layers of semi-rounded nodules, each thinly coated with a veneer (typically 1 mm thick) of lava. The nodule beds are analogous to cobble deposits of fluvial sedimentary systems. Although several mechanisms have been proposed for the formation of the nodule beds, it was found that, at more than one locality, the nodule beds are overbank levee deposits. The geological occurrence of the nodules, certain diagnostic aspects of the flow morphology and consideration of the inferred emplacement process indicate that the Kaupulehu flow had an exceptionally low viscosity on eruption and that the flow of the lava stream was extremely rapid, with flow velocities of at least 10 m s–1 (more than 40 km h–1). This flow is the youngest on Hualalai Volcano and future eruptions of a similar type would pose considerable hazard to life as well as property.

Electronic Resource

1432-0819

Key words: Fractals ; lava ; rheology ; remote sensing

Springer Online Journal Archives 1860-2000

Geosciences

Abstract. This study aims at quantifying the effect of rheology on plan-view shapes of lava flows using fractal geometry. Plan-view shapes of lava flows are important because they reflect the processes governing flow emplacement and may provide insight into lava-flow rheology and dynamics. In our earlier investigation (Bruno et al. 1992), we reported that flow margins of basalts are fractal, having a characteristic shape regardless of scale. We also found we could use fractal dimension (D, a parameter which quantifies flow-margin convolution) to distinguish between the two endmember types of basalts: a′a (D: 1.05–1.09) and pahoehoe (D: 1.13–1.23). In this work, we confirm those earlier results for basalts based on a larger database and over a wider range of scale (0.125 m–2.4 km). Additionally, we analyze ten silicic flows (SiO2: 52–74%) over a similar scale range (10 m–4.5 km). We note that silicic flows tend to exhibit scale-dependent, or non-fractal, behavior. We attribute this breakdown of fractal behavior at increased silica contents to the suppression of small-scale features in the flow margin, due to the higher viscosities and yield strengths of silicic flows. These results suggest we can use the fractal properties of flow margins as a remote-sensing tool to distinguish flow types. Our evaluation of the nonlinear aspects of flow dynamics indicates a tendency toward fractal behavior for basaltic lavas whose flow is controlled by internal fluid dynamic processes. For silicic flows, or basaltic flows whose flow is controlled by steep slopes, our evaluation indicates non-fractal behavior, consistent with our observations.

Electronic Resource

1432-0819

fractals ; lava ; rheology ; remote sensing

Springer Online Journal Archives 1860-2000

Geosciences

Abstract This study aims at quantifying the effect of rheology on plan-view shapes of lava flows using fractal geometry. Plan-view shapes of lava flows are important because they reflect the processes governing flow emplacement and may provide insight into lava-flow rheology and dynamics. In our earlier investigation (Bruno et al. 1992), we reported that flow margins of basalts are fractal, having a characteristic shape regardless of scale. We also found we could use fractal dimension (D, a parameter which quantifies flow-margin convolution) to distinguish between the two endmember types of basalts: a′ a (D: 1.05–1.09) and pahoehoe (D: 1.13–1.23). In this work, we confirm those earlier results for basalts based on a larger database and over a wider range of scale (0.125 m–2.4 km). Additionally, we analyze ten silicic flows (SiO2: 52–74%) over a similar scale range (10 m–4.5 km). We note that silicic flows tend to exhibit scale-dependent, or non-fractal, behavior. We attribute this breakdown of fractal behavior at increased silica contents to the suppression of small-scale features in the flow margin, due to the higher viscosities and yield strengths of silicic flows. These results suggest we can use the fractal properties of flow margins as a remote-sensing tool to distinguish flow types. Our evaluation of the nonlinear aspects of flow dynamics indicates a tendency toward fractal behavior for basaltic lavas whose flow is controlled by internal fluid dynamic processes. For silicic flows, or basaltic flows whose flow is controlled by steep slopes, our evaluation indicates non-fractal behavior, consistent with our observations.

Electronic Resource

1573-5036

breeding ; chromosome ; copper ; copper-efficiency ; Triticum aestivum ; wheat-rye

Springer Online Journal Archives 1860-2000

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Abstract A greenhouse study was conducted to determine the Cu-efficiency of 5A/5RL wheat-rye translocation lines and nine wheat genotypes grown in a Cu-deficient orthic dark grey chernozemic soil. The soil used was characterized by pH 5.4 and 0.48 μg Cu g−1 soil (DTPA), and was obtained from a known Cu-deficient site at Stony Plain, Central Alberta. Twelve genotypes (three 5A/5RL wheat-rye translocation lines and nine wheat cultivars) and two Cu treatments (soil amended with 145 μg Cu kg−1 soil, and non-amended) were used. The efficiency for Cu use was evaluated for grain yield and yield components. 5A/5RL wheat-rye translocation lines individually and as a group showed significantly (p〈0.05) higher grain yield both in +Cu and −Cu treatments compared to wheat genotypes without the wheat-rye chromosome translocation. 5A/5RL wheat-rye translocation lines demonstrated Cu-efficiency ranging from 70–127% for grain yield. Only two wheat cultivars (Kenya Leopard and Columbus) showed comparable efficiency (70 and 76% respectively). Wheat cultivars Kwale, Kenya Tausi, Roblin, Katepwa, Park, Oslo and Biggar showed low Cu-efficiency (10–36%). The study confirms that the 5A/5RL wheat-rye translocation confers useful levels of Cu-efficiency to wheat, that can be used as an additional source of variability in breeding programs. ei]L V Kochian

Electronic Resource

1573-5036

relative addition rate ; relative growth rate ; traditional solution culture ; Triticum aestivum

Springer Online Journal Archives 1860-2000

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Abstract The relative addition rate (RAR) technique allows the nutritional control of plant relative growth rate (RGR) by the provision of nutrients at exponential supply rates. The technique, however, was developed with technologically sophisticated aeroponic systems. In this paper, we report on experiments used to adapt the RAR technique to a conventional solution culture system. A background concentration requirement of 36 μM nitrogen (N), with other nutrients supplied in proportion to N, was necessary to produce a constant RGR of Triticum aestivum L. (wheat) at a low RAR. Solution pH changes were reduced by increasing the percentage of NH4 in the nitrogen supply, but the plants exhibited dry weight reductions and symptoms of toxicity above 30% NH4. For wheat, a ratio of 25/75 NH4/NO3 was optimum for minimizing pH changes within the nontoxic range. A test of the effectiveness of the RAR technique using this background concentration and NH4/NO3 ratio showed that RGR increased with RAR with a linear slope of 0.55 and an intercept of 0.07 d-1. Although the relationship between growth rate and nutrient supply was less than the one-to-one dependence of RGR on RAR that has been obtained with more sophisticated apparatus, application of the RAR technique to a conventional solution culture system still affords considerable control of RGR and presents a simple method for growing plants at different levels of nutrient stress and at distinct RGRs.

Electronic Resource

1573-5036

chlorophyll ; genotypic differences ; leaf elongation rate ; Mn toxicity ; Mn tolerance ; screening ; Triticum aestivum L. ; wheat

Springer Online Journal Archives 1860-2000

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Abstract After aluminum toxicity, manganese (Mn) toxicity is probably the second most important growth limiting factor in acid soils. The purpose of this study was to determine the feasibility of using chlorophyll content and leaf elongation rate (LER) for regrowth of Mn stressed seedlings as a rapid seedling based screening bioassay for Mn tolerance in segregating populations of wheat (Triticum aestivum L.). In one experiment, chlorophyll was determined for the cultivars Norquay (Mn-tolerant) and Columbus (Mn-sensitive) subjected to twelve Mn levels (2 to 2000 μM) in nutrient solutions. As Mn concentration increased, chlorophyll ‘a’ and ‘b’ contents of the Mn-tolerant cultivar decreased up to 9%, while in the Mn-sensitive cultivar it was reduced by as much as 43%. The chlorophyll ‘a/b’ ratio did not differ among Mn concentrations for either cultivar. In a second experiment, chlorophyll content and LER for regrowth of Mn stressed seedlings (1000 μM) was determined for Columbus and Katepwa (Mn-sensitive), Oslo (Mn-intermediate), and Norquay and Laura (Mn-tolerant). Manganese tolerance as assayed by chlorophyll ‘a’ and ‘b’ and LER was significantly correlated with Mn tolerance as assayed by the relative root weight methodology (RRW). Thus, chlorophyll content of Mn-stressed seedlings and LER of seedling regrowth appear to be suitable techniques for screening unreplicated selections of segregating populations for tolerance to Mn.

Electronic Resource

1573-5036

aluminium resistance ; doubled-haploid lines ; near-isogenic lines ; root exudate polypeptide ; Triticum aestivum

Springer Online Journal Archives 1860-2000

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Abstract We have made use of a genetic approach to develop homozygous, near-isogenic germplasm for investigating aluminium (Al) resistance in Triticum aestivum L. A conventional backcross program was used to transfer Al resistance from the Al-resistant cultivar, Maringa, to a locally-adapted, Al-sensitive cultivar, Katepwa. At the third backcross stage, a single, resistant isoline (Alikat = Katepwa*3/Maringa) was chosen on the basis of superior root growth after 14 days of exposure to a broad range of Al concentrations (0 to 600 µM). Genetic analysis of doubled-haploid lines (DH) developed from this isoline suggested that resistance is controlled by a single dominant gene. Crosses between DH Alikat and DH Katepwa yielded an Al-resistant F1 population. Backcrossing this F1 population to DH Katepwa produced a population which segregated 1:1 for Al resistance, while selfing produced a population segregating 3 : 1 for Al resistance. Under conditions of Al stress, Al-resistant F2 plants released a suite of novel low molecular weight polypeptides into the rhizosphere. One of these polypeptides (23 kD) shows substantive Al-binding capacity and segregates with the resistant phenotype. While the precise mechanisms that mediate Al resistance are still unknown, this research has provided support for a possible role of the 23 kD exudate polypeptide in mediating resistance to Al. To more fully understand the role that this polypeptide plays in Al-resistance, we are attempting to clone this gene from microsequence data obtained from purified protein.

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