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- Quentin, Audrey G, et al.
(författare)
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Non-structural carbohydrates in woody plants compared among laboratories.
- 2015
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Ingår i: Tree physiology. - : Oxford University Press (OUP). - 1758-4469 .- 0829-318X. ; 35:11, s. 1146-1165
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Tidskriftsartikel (refereegranskat)abstract
- Non-structural carbohydrates (NSC) in plant tissue are frequently quantified to make inferences about plant responses to environmental conditions. Laboratories publishing estimates of NSC of woody plants use many different methods to evaluate NSC. We asked whether NSC estimates in the recent literature could be quantitatively compared among studies. We also asked whether any differences among laboratories were related to the extraction and quantification methods used to determine starch and sugar concentrations. These questions were addressed by sending sub-samples collected from five woody plant tissues, which varied in NSC content and chemical composition, to 29 laboratories. Each laboratory analyzed the samples with their laboratory-specific protocols, based on recent publications, to determine concentrations of soluble sugars, starch and their sum, total NSC. Laboratory estimates differed substantially for all samples. For example, estimates for Eucalyptus globulus leaves (EGL) varied from 23 to 116 (mean = 56) mg g(-1) for soluble sugars, 6-533 (mean = 94) mg g(-1) for starch and 53-649 (mean = 153) mg g(-1) for total NSC. Mixed model analysis of variance showed that much of the variability among laboratories was unrelated to the categories we used for extraction and quantification methods (method category R(2) = 0.05-0.12 for soluble sugars, 0.10-0.33 for starch and 0.01-0.09 for total NSC). For EGL, the difference between the highest and lowest least squares means for categories in the mixed model analysis was 33 mg g(-1) for total NSC, compared with the range of laboratory estimates of 596 mg g(-1). Laboratories were reasonably consistent in their ranks of estimates among tissues for starch (r = 0.41-0.91), but less so for total NSC (r = 0.45-0.84) and soluble sugars (r = 0.11-0.83). Our results show that NSC estimates for woody plant tissues cannot be compared among laboratories. The relative changes in NSC between treatments measured within a laboratory may be comparable within and between laboratories, especially for starch. To obtain comparable NSC estimates, we suggest that users can either adopt the reference method given in this publication, or report estimates for a portion of samples using the reference method, and report estimates for a standard reference material. Researchers interested in NSC estimates should work to identify and adopt standard methods.
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- Landhausser, S. M., et al.
(författare)
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Standardized protocols and procedures can precisely and accurately quantify non-structural carbohydrates
- 2018
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 38:12, s. 1764-1778
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Tidskriftsartikel (refereegranskat)abstract
- Non-structural carbohydrates (NSCs), the stored products of photosynthesis, building blocks for growth and fuel for respiration, are central to plant metabolism, but their measurement is challenging. Differences in methods and procedures among laboratories can cause results to vary widely, limiting our ability to integrate and generalize patterns in plant carbon balance among studies. A recent assessment found that NSC concentrations measured for a common set of samples can vary by an order of magnitude, but sources for this variability were unclear. We measured a common set of nine plant material types, and two synthetic samples with known NSC concentrations, using a common protocol for sugar extraction and starch digestion, and three different sugar quantification methods (ion chromatography, enzyme, acid) in six laboratories. We also tested how sample handling, extraction solvent and centralizing parts of the procedure in one laboratory affected results. Non-structural carbohydrate concentrations measured for synthetic samples were within about 11.5% of known values for all three methods. However, differences among quantification methods were the largest source of variation in NSC measurements for natural plant samples because the three methods quantify different NSCs. The enzyme method quantified only glucose, fructose and sucrose, with ion chromatography we additionally quantified galactose, while the acid method quantified a large range of mono- and oligosaccharides. For some natural samples, sugars quantified with the acid method were two to five times higher than with other methods, demonstrating that trees allocate carbon to a range of sugar molecules. Sample handling had little effect on measurements, while ethanol sugar extraction improved accuracy over water extraction. Our results demonstrate that reasonable accuracy of NSC measurements can be achieved when different methods are used, as long as protocols are robust and standardized. Thus, we provide detailed protocols for the extraction, digestion and quantification of NSCs in plant samples, which should improve the comparability of NSC measurements among laboratories.
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| 4. |
- Stewart, Alexander F., et al.
(författare)
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Chemistry Writing Instruction and Training: Implementing a Comprehensive Approach to Improving Student Communication Skills
- 2016
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Ingår i: Journal of Chemical Education. - : American Chemical Society (ACS). - 0021-9584 .- 1938-1328. ; 93:1, s. 86-92
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Tidskriftsartikel (refereegranskat)abstract
- The ability of science undergraduate students to capably communicate course content and their understanding of scientific phenomena through writing has long been considered a problem. Effective methods for improving student writing skills are often fragmented and undertaken on a course-by-course basis rather than as a coordinated approach. This paper describes the implementation of a departmental effort to enhance and evaluate chemistry student writing in several upper-year laboratory courses. The program involves introducing extensive writing focused aspects to course assignments and reports and has impacted over 600 students during a six-year period. Student feedback has been exceptionally positive from undergraduates as well as graduate students who previously participated in the initiative.
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| 5. |
- Wheeler, J. A., et al.
(författare)
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With a little help from my friends : community facilitation increases performance in the dwarf shrub Salix herbacea
- 2015
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791 .- 1618-0089. ; 16:3, s. 202-209
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Tidskriftsartikel (refereegranskat)abstract
- Shifts between positive and negative plant interactions along environmental stress gradients can affect alpine plant performance. We removed neighbours around Salix herbacea, a common arctic and alpine dwarf shrub, along elevational and snowmelt gradients on three mountains in Switzerland. The objectives of our study were to determine the effect of neighbours on phenological, morphological, and fitness traits ofS. herbacea, and to determine whether neighbour interactions shift from competition to facilitation along environmental stress gradients.Target plants without neighbours required less time for fruit production; however, they also were more likely to be damaged by caterpillar herbivory. Effects of neighbour removal changed along the environmental gradients: plants without neighbours had smaller leaves on earlier snowmelt sites, and increased fungal damage with increasing elevation. Without neighbour removal, damage generally led to reduced female flowering under later snowmelt conditions in the following summer.Our results indicate that the majority of neighbour interactions influencing S. herbacea are facilitative, particularly at stressful early snowmelt and high elevation sites. We suggest that neighbours moderate environmental conditions by protecting plants from temperature extremes, and reduce plant apparency to caterpillars. Neighbours also indirectly increase fitness by reducing damage. Facilitation by neighbours may become more important under climate change, as early snowmelt may increase stress.
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