Adjustment of growth and central metabolism to a mild but sustained nitrogen-limitation in Arabidopsis

We have established a simple soil-based experimental system that allows a small and sustained restriction of growth of Arabidopsis by low nitrogen (N). Plants were grown in a large volume of a peat–vermiculite mix that contained very low levels of inorganic N. As a control, inorganic N was added in solid form to the peat–vermiculite mix, or plants were grown in conventional nutrient-rich solids. The low N growth regime led to a sustained 20% decrease of the relative growth rate over a period of 2 weeks, resulting in a two- to threefold decrease in biomass in 35- to 40-day-old plants. Plants in the low N regime contained lower levels of nitrate, lower nitrate reductase activity, lower levels of malate, fumarate and other organic acids and slightly higher levels of starch, as expected from published studies of N-limited plants. However, their rosette protein content was unaltered, and total and many individual amino acid levels increased compared with N-replete plants. This metabolic phenotype reveals that Arabidopsis responds adaptively to low N by decreasing the rate of growth, while maintaining the overall protein content, and maintaining or even increasing the levels of many amino acids.     

Light acclimation of Chlamydomonas acidophila accumulating in the hypolimnion of an acidic lake (pH 2.6)

1. The unicellular green alga Chlamydomonas acidophila accumulates in a thin phytoplankton layer in the hypolimnion (deep chlorophyll maximum, DCM) of an extremely acidic lake (Lake 111, pH 2.6, Lusatia, Germany), in which the underwater light spectrum is distorted and red‐shifted. 2. Chlamydomonas acidophila exhibited a significantly higher absorption efficiency and a higher cellular chlorophyll b content when incubated in the red shifted underwater light of Lake 111 than in a typical, blue‐green dominated, light spectrum. 3. Chlamydomonas acidophila has excellent low light acclimation properties (increased chlorophyll b content, increased oxygen yield and a low light saturation point for photosynthesis) that support survival of the species in the low light climate of the DCM. 4. In situ acclimation to the DCM under low light and temperature decreased maximum photosynthetic rate in autotrophic C. acidophila cultures, whereas the presence of glucose under these conditions enhanced photosynthetic efficiency and capacity. 5. The adaptive abilities of C. acidophila to light and temperature shown in this study, in combination with the absence of potent competitors because of low lake pH, most probably enable the unusual dominance of the green alga in the DCM of Lake 111.     

Formation of aerenchyma in roots of Zea mays in aerated solutions, and its relation to nutrient supply

The formation of lysigenous cavities (aerenchyma) in the root cortex of maize, Zea mays L. cv. Capella, under well-aerated conditions has been studied in relation to the composition of the nutrient solutions. Nitrogen, either supplied as nitrate or as ammonium, reduced the cavity formation by the roots. This reduction was most apparent at nitrate concentrations above 2 mM. Cavities were increasingly formed when the nitrate concentration was decreased and they reached their largest dimensions in roots growing in water. Thus, inadequate availability of nitrogen leads, under acrated conditions, to deterioration of cortex cells and cavity formation in the maize roots. It is suggested that cavity formation in these roots is connected with reduced nitrogen assimilation.     

SENSORY ANALYSIS IN MARKETING PRACTICE: COMPARISON AND INTEGRATION

Sensory analysis has traditionally played a prominent role in quality control for food products. More and more principles from sensory analysis are also applied in the area of food product development, bringing sensory analysis more closely into the domain of marketing. Unfortunately, in practice integration between sensory and marketing practices is far from optimal. Differences in basic orientations between sensory and marketing are a major source contributing to this defective cooperation.
Sensory analysis has traditionally been product oriented with an emphasis on internal validity of the test results. Implicitly or explicitly this approach emphasizes the relationships between sensory evaluation and characteristics of the product. Marketing, on the other hand, stresses the external validity of test results: the extent to which test results can be generalized to market behavior. Emphasis on external validity requires an approach to sensory analysis that is fundamentally different from current sensory practice in terms of type of respondents, type of stimuli, scaling procedures adopted and test circumstances.
Closer integration between the product and consumer oriented approach to sensory analysis may contribute to the success of product development in the food industry. The literature suggests several factors that may contribute to a more fruitful cooperation between the two approaches to sensory analysis. The company's senior management plays a central role in the achievement of this integration by providing an infrastructure (in terms of personnel, organizational structure and financial resources) that paves the way for closer cooperation.     

The Ocruranus–Eohalobia group of small shelly fossils from the Lower Cambrian of Yunnan

Lower Cambrian phosphorite samples from Maotianshan, Yunnan Province, South China, yielded a variety of small shelly fossils. Sclerites of the second pre-trilobite faunal assemblage of Meishucun, the Paragbborilus-Siphogonuchites–Lapworthella association of Nemakit–Daldynian to Tommotían age, were dominant. They comprise previously unknown spine-bearing specimens of Ocruranus finial Liu, 1979, and new morphotypes of Eohalobia diandongensis Jiang, 1982. Well-preserved sclerites reveal a laminated, composite fine structure with marginal, incremental growth. Each lamella consists of radial series of minute growth elements. The shells are phosphatically preserved, but micropetrographic evidence from drill-core samples indicates calcium carbonate as primary shell material. In the light of this new evidence, Ocruranus–Eohalobia group fossils are interpreted as parts of coeloscleritophoran scleritomes.     

A new species of Cryptolepis (Periplocoideae, Apocynaceae) from Arabia

A new species of Cryptolepis from Yemen, Arabian Peninsula, C. yemenensis is described and figured. It is recognized by the glabrous appearance of the plant, oblong-elliptic to narrowly obovate leaves, small flowers, small follicles and ridged seed. The new species resembles Cryptolepis gillettii Hutch. & E.A. Bruce and C. volubilis (Balf f.) Schwartz to some extent. Their flowers are die, except for size and different corona shapes. However, they differ with regard to the shape and size of the follicles, the texture of the seed coat and the absence or presence of vesture on the plants.     

Xeml Lab: a tool that supports the design of experiments at a graphical interface and generates computer-readable metadata files, which capture information about genotypes, growth conditions, environmental perturbations and sampling strategy

Data mining depends on the ability to access machine-readable metadata that describe genotypes, environmental conditions, and sampling times and strategy. This article presents Xeml Lab. The Xeml Interactive Designer provides an interactive graphical interface at which complex experiments can be designed, and concomitantly generates machine-readable metadata files. It uses a new eXtensible Mark-up Language (XML)-derived dialect termed XEML. Xeml Lab includes a new ontology for environmental conditions, called Xeml Environment Ontology. However, to provide versatility, it is designed to be generic and also accepts other commonly used ontology formats, including OBO and OWL. A review summarizing important environmental conditions that need to be controlled, monitored and captured as metadata is posted in a Wiki ( http://www.codeplex.com/XeO ) to promote community discussion. The usefulness of Xeml Lab is illustrated by two meta-analyses of a large set of experiments that were performed with Arabidopsis thaliana during 5 years. The first reveals sources of noise that affect measurements of metabolite levels and enzyme activities. The second shows that Arabidopsis maintains remarkably stable levels of sugars and amino acids across a wide range of photoperiod treatments, and that adjustment of starch turnover and the leaf protein content contribute to this metabolic homeostasis.     

Chemical composition of 24 wild species differing in relative growth rate

The chemical composition of 24 plant species which showed a three-fold range in potential growth rate was investigated. The carbon content of whole plants was lower for fast-growing species than for slow-growing ones. Fast-growing species accumulated more organic N-compounds, organic acids and minerals, whereas slow-growing species accumulated more (hemi)cellulose, insoluble sugars and lignin. No correlations with relative growth rate were found for soluble phenolics, soluble sugars and lipids. The costs to construct 1 g of plant biomass were rather similar for fast- and slow-growing species, both when expressed as C needed for C-skeletons, as glucose to provide ATP and NAD(P)H, and as total glucose costs. Therefore, we conclude that, despite the differences in chemical composition between fast- and slow-growing species, variation in the costs of synthesis of whole plant biomass cannot explain interspecific variation in relative growth rate of herbaceous species.