Search results for "component"

Mannitol-producing tobacco exposed to varying levels of water, light, temperature and paraquat

2007

Transgenic mannitol-producing (+mtlD) and wild-type (-mtlD) tobacco plants were exposed to water deficit, varying light intensities, low temperatures, and paraquat applications to test whether mannitol was involved in protection against abiotic stresses. In the water deficit experiment, -mtlD and +mtlD plants were fully irrigated [100% evapotranspiration (ET)] or received 25% ET for 40 d. Water deficit reduced the relative water content (RWC) of both types of plant starting on day 22 and the total stem length (TSL) of -mtlD 25% ET plants after 11 d, whereas TSL of +mtlD 25% ET was reduced only after 34 d. After 30 days of water deficit, a higher percentage of mature foliage was retained by …

Factors controlling planktonic size spectral responses to autumnal circulation in a Mediterranean lake

2006

14 pages, and figures, and tables statistics.

Review paper: Seasonal variation as a determinant of population structure in rotifers reproducing by cyclical parthenogenesis

1998

Monogonont rotifers live in habitats that display extensively variation in both biotic and abiotic components. Much of this variation is seasonal and therefore predictable for a given pond or lake. In 1972, King proposed one physiological and two genetic models presenting alternative modes of adaptation to this temporal variation. Our purpose in the present paper is to review and evaluate how our knowledge of the seasonal structure of rotifer populations has changed in the past 25 years. Seasonal changes in clone frequencies have been reported from three studies of natural populations using electrophoretic analysis of isozymes. In one of these studies there was evidence for substantial temp…

2011

Natural communities are structured by intra-guild competition, predation or parasitism and the abiotic environment. We studied the relative importance of these factors in two host-social parasite ecosystems in three ant communities in Europe (Bavaria) and North America (New York, West Virginia). We tested how these factors affect colony demography, life-history and the spatial pattern of colonies, using a large sample size of more than 1000 colonies. The strength of competition was measured by the distance to the nearest competitor. Distance to the closest social parasite colony was used as a measure of parasitism risk. Nest sites (i.e., sticks or acorns) are limited in these forest ecosyst…

Ammonoid recovery after the Permian-Triassic mass extinction: a re-exploration of morphological and phylogenetic diversity patterns.

2013

The explosive ammonoid rediversification after the Permian–Triassic mass extinction is now well understood in terms of taxonomic richness and biogeography. Using an updated dataset of Early Triassic ammonoids, we compare morphological disparity and taxonomic richness patterns at the regional and global scales. Disparity evolved similarly at both scales, suggesting a global influence of abiotic factors. Morphological diversification occurred early in the Smithian and a marked contraction of the morphospace took place during the end-Smithian extinction. We confirm that trends in disparity and richness were decoupled during the Griesbachian and Dienerian. Three macroevolutionary processes may …

Epiphytes and associated fauna on the brown alga Fucus vesiculosus in the Baltic and the North Seas in relation to different abiotic and biotic varia…

2011

Fucus vesiculosus L. is an important habitat-forming macroalga both in the saline and high diverse North Sea and the diluted and low diversity Baltic Sea. Despite its importance, comparisons of the spatial patterns of its epiphytes have rarely been reported. In this study we examined the species composition and density of macro-epiphytes and mobile fauna on the canopy-forming macroalga F. vesiculosus inhabiting different regimes of wave exposure in the North and Baltic Seas. The North and Baltic Seas had distinct epiphyte and mobile faunal communities. Wave exposure and segments of host fronds significantly contributed to the variability in species composition and dominance structure of epi…

2021

In fish, the lipid resources of the female form a link between the environment and progeny, contributing to the contents of the egg yolk. Variation of the environmental conditions is therefore expected to affect the egg quality via maternal pathways, reflecting the female’s response to the environmental factors before spawning. We investigated the content of lipids and thyroid hormones in the ovary and eggs of the Baltic herring during 1988–2019, when salinity of the Baltic Sea first declined and then stabilized to a lower level, and winters varied between severe and mild. The total lipid resources of spawning females decreased by 40–50% during the study, and the ovarian lipid concentration…

The importance of the moss layer in sustaining biological diversity of Gamasina mites in coniferous forest soil

2008

Summary The feather moss layer of boreal coniferous forests is known to buffer the underlying soil temperature and to be a major component in the nitrogen and phosphorus cycles by efficient scavenging of nutrients from throughfall and direct precipitation. Through indirect or direct effects the feather moss layer may also play a significant role in forming soil organism communities. In this 4-year experimental field study, the predatory Gamasina mite diversity was estimated in plots where the feather moss layer was removed or disturbed by turning over, in relation to that in control plots. Species richness, Shannon's diversity and equitability in spring but not autumn were decreased when th…

Breeding For Organic Farming : Obtaining And Evaluation Of Flax Somaclonal Families

2015

Plant calli culture could be used as a source of genetic changes (somaclonal variation). There are known several flax varieties, bred on the basis of somaclonal variation, with improved resistance to biotic and abiotic stresses, plant height, seed yield and other traits. This method is useful for obtaining the new initial material for flax breeding, including for intensification of breeding for organic farming. Goal of the study was to obtain plants-regenerants from the calli culture of the fibre flax variety ‘Vega 2’ and to evaluate their agronomical traits and resistance to powdery mildew. For obtaining plants-regenerants was used early elaborated protocol of somatic calli cultivation. Ag…

Genetic Engineering Strategies for Abiotic Stress Tolerance in Plants

2015

Crop plants are affected by a variety of abiotic stresses such as salinity, drought, extreme temperatures, and oxidative stress and cause a significant yield loss (more than 50 %). In the near future, these abiotic stresses might increase because of global climate change. Abiotic stresses lead to dehydration or osmotic stress through reduced availability of water for vital cellular functions and maintenance of turgor pressure and also result in high production of reactive oxygen species (ROS). Plants are evolved with various mechanisms such as changes in cellular and metabolic processes to cope with the stress condition. Recent developments in molecular genetics have contributed greatly to …