Nutritional Constraints (nutritional + constraint)

Distribution by Scientific Domains


Selected Abstracts


Nutritional constraints in ombrotrophic Sphagnum plants under increasing atmospheric nitrogen deposition in Europe

NEW PHYTOLOGIST, Issue 3 2004
Luca Bragazza
Summary ,,We studied the effects of increasing levels of atmospheric nitrogen (N) deposition on nutrient limitation of ombrotrophic Sphagnum plants. ,,Fifteen mires in 11 European countries were selected across a natural gradient of bulk atmospheric N deposition from 0.1 to 2 g/m2 year,1. Nutritional constraints were assessed based on nutrient ratios of N, phosphorus (P), and potassium (K) in Sphagnum plants collected in hummocks (i.e. relatively drier microhabitats) and in lawns (i.e. relatively wetter microhabitats). ,,Nutrient ratios in Sphagnum plants increased steeply at low atmospheric N input, but above a threshold of N deposition of c. 1 g/m2 year,1 the N : P and N : K ratios tended to saturation. Increasing atmospheric N deposition was also accompanied by a reduced retention of Ca and Mg in Sphagnum plants and a decreased stem volumetric density in hummock Sphagnum plants. ,,We suggest a critical load of N deposition in Europe of 1 g/m2 year,1 above which Sphagnum plants change from being N-limited to be K + P colimited, at N : P > 30 and N : K > 3. [source]


Effect of drying and storage on the degradation of total carotenoids in orange-fleshed sweetpotato cultivars

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2010
Aurélie Bechoff
Abstract BACKGROUND: Orange-fleshed sweetpotato (OFSP) can be used to tackle vitamin A deficiency, a major public health problem in most developing countries. In East Africa, common ways of using sweetpotato include drying and subsequent storage. The aim of the study was to investigate the impact of drying and storage on the total carotenoid retention (as an estimate of provitamin A retention) from OFSP. RESULTS: Losses of total carotenoid during drying were generally low (15% or less). Total carotenoid retention in OFSP was not dependent on the type of dryer (solar or sun). Sweetpotato cultivar (Ejumula, Kakamega, SPK004/1, SPK004/1/1, SPK004/6 or SPK004/6/6) had a significant effect on retention in drying (P < 0.05). High percentage losses of total carotenoids were, however, correlated with high moisture content and high carotenoid content in fresh sweetpotato roots. After 4 months' storage at room temperature in Uganda, losses of total carotenoid in dried sweetpotato chips were high (about 70%) and this was not dependent on the use of opaque or transparent packaging. CONCLUSION: Losses of carotenoids during storage were considered to be more of a nutritional constraint to the utilisation of dried sweetpotato than losses occurring during drying. The relationship between characteristics of the cultivars and losses of carotenoids during drying should be taken into account in selection of cultivars for processing. Copyright © 2009 Society of Chemical Industry [source]


Restoration of body mass in King Penguins after egg abandonment at a critical energy depletion stage: early vs late breeders

JOURNAL OF AVIAN BIOLOGY, Issue 4 2001
Jean-Patrice Robin
In fasting-incubating seabirds, it has been proposed that egg abandonment and refeeding should be induced when a low body mass (BM) threshold is attained, thus ensuring adult survival at the expense of immediate breeding. In the context of life-history trade-offs in long-lived birds, we have tested this hypothesis by comparing short-term survival and restoration of BM in King Penguins Aptenodytes patagonicus that abandoned their egg to those that were relieved normally by their mate at the end of the first incubation shift. Since King Penguins have an extended laying period, the possible influence of seasonal factors was also examined by comparing early and late breeders. Forty incubating males were experimentally forced to fast until egg abandonment by preventing relief by the female. At egg abandonment of both early and late breeding males, BM was below the BM threshold, fasting duration was eight days (about 30%) longer than for relieved birds, and plasma uric acid level was elevated (signature of increased body protein catabolism, phase III of fasting). All abandoning birds survived and came back from sea at a BM similar to that of relieved penguins. The duration of the foraging trip of abandoning early breeders was the same as that of relieved birds, and some abandoning birds engaged in a new breeding attempt. Abandoning late breeders, however, made foraging trips twice as long as those of relieved males. This difference can be explained by time constraints rather than nutritional constraints, abandoning early breeders having enough time left in the breeding season to engage in a new breeding attempt in contrast to abandoning late breeders. These observations lend support to the suggestion that not only BM but also an internal clock intervene in the decision to engage in breeding or not. By preventing a lethal energy depletion ashore and by acting at a fasting stage where the capacity to restore BM at sea is unaffected, abandonment at a low body condition threshold plays a major role in the trade-off between adult penguin survival and reproduction. [source]


Docosahexaenoic acid, the aquatic diet, and hominin encephalization: Difficulties in establishing evolutionary links

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2007
Bryce A. Carlson
Distinctive characteristics of modern humans, including language, tool manufacture and use, culture, and behavioral plasticity, are linked to changes in the organization and size of the brain during hominin evolution. As brain tissue is metabolically and nutritionally costly to develop and maintain, early hominin encephalization has been linked to a release of energetic and nutritional constraints. One such nutrient-based approach has focused on the n -3 long-chained polyunsaturated fatty acid docosahexaenoic acid (DHA), which is a primary constituent of membrane phospholipids within the synaptic networks of the brain essential for optimal cognitive functioning. As biosynthesis of DHA from n -3 dietary precursors (alpha-linolenic acid, LNA) is relatively inefficient, it has been suggested that preformed DHA must have been an integral dietary constituent during evolution of the genus Homo to facilitate the growth and development of an encephalizing brain. Furthermore, preformed DHA has only been identified to an appreciable extent within aquatic resources (marine and freshwater), leading to speculation that hominin encephalization is linked specifically to access and consumption of aquatic resources. The key premise of this perspective is that biosynthesis of DHA from LNA is not only inefficient but also insufficient for the growth and maturation demands of an encephalized brain. However, this assumption is not well-supported, and much evidence instead suggests that consumption of LNA, available in a wider variety of sources within a number of terrestrial ecosystems, is sufficient for normal brain development and maintenance in modern humans and presumably our ancestors. Am. J. Hum. Biol. 19:132,141, 2007. © 2006 Wiley-Liss, Inc. [source]