Accumulation Decreased (accumulation + decreased)

Distribution by Scientific Domains

Selected Abstracts

Accumulation of 137Cs by larvae of the midge Chironomus riparius from sediment: Effect of potassium

Lieven Bervoets
Abstract We studied the effect of potassium on the uptake of radiocesium from sediment by larvae of the midge Chironomus riparius. Sediment ingestion rate was determined for one week. After 24 h the gut content remained constant, indicating that equilibrium was reached between sediment ingestion and sediment elimination. These data were used to account for radiocesium present in the gut in subsequent uptake experiments. Reference sediment was equilibrated with solutions containing different concentrations of potassium: 1, 10, 100, and 1,000 ,M. Adsorption of 137Cs to the sediment was investigated. Three different radiocesium levels (0.3, 0.6, and 1.2 KBq/ml) were applied at the four different potassium levels. In all cases more than 94% of all radiocesium was adsorbed to the sediment within 48 h. The sediment, equilibrated with the four different potassium levels, was spiked with a constant amount of 296 Bq/ml 137Cs. Accumulation by midge larvae was followed for one week, and subsequently elimination was followed for another week. No significant differences in radiocesium levels in midge larvae among the treatments were found after one week of exposure. However, using a one-compartment accumulation model, a small but significant effect of potassium in water and sediment on the uptake and elimination rate constants (ka and ke) was found. These results indicate that although differences were rather small, radiocesium accumulation decreased with increasing potassium level in the sediment. [source]

Variation in Heat-shock Proteins and Photosynthetic Thermotolerance among Natural Populations of Chenopodium album L. from Contrasting Thermal Environments: Implications for Plant Responses to Global Warming

Deepak Barua
Abstract Production of heat-shock proteins (Hsps) is a key adaptation to acute heat stress and will be important in determining plant responses to climate change. Further, intraspecifc variation in Hsps, which will influence species-level response to global warming, has rarely been examined in naturally occurring plants. To understand intraspecific variation in plant Hsps and its relevance to global warming, we examined Hsp content and thermotolerance in five naturally occurring populations of Chenopodium album L. from contrasting thermal environments grown at low and high temperatures. As expected, Hsp accumulation varied between populations, but this was related more to habitat variability than to mean temperature. Unexpectedly, Hsp accumulation decreased with increasing variability of habitat temperatures. Hsp accumulation also decreased with increased experimental growth temperatures. Physiological thermotolerance was partitioned into basal and induced components. As with Hsps, induced thermotolerance decreased with increasing temperature variability. Thus, populations native to the more stressful habitats, or grown at higher temperatures, had lower Hsp levels and induced thermotolerance, suggesting a greater reliance on basal mechanisms for thermotolerance. These results suggest that future global climate change will differentially impact ecotypes within species, possibly by selecting for increased basal versus inducible thermotolerance. [source]

Fruit load and elevation affect ethylene biosynthesis and action in apple fruit (Malus domestica L. Borkh) during development, maturation and ripening

ABSTRACT The influence of internal and external factors such as tree fruit load and elevation on ethylene biosynthesis and action was assessed during apple fruit development and ripening. Ethylene biosynthesis, as well as transcript accumulation of the hormone biosynthetic enzymes (MdACS1 and MdACO1), receptors (MdETR1 and MdERS1) and an element of the transduction pathway (MdCTR1), were evaluated in apples borne by trees with high (HL) and low (LL) fruit load. Orchards were located in two localities differing in elevation and season day degree sum. These parameters significantly affected the date of bloom and commercial harvest, and the length of the fruit developmental cycle. Trees from the low elevation (LE) bloomed and the fruit ripened earlier than those from the high elevation (HE), displaying also a shortened fruit developmental cycle. Dynamics of ethylene evolution was apparently not affected by elevation. The onset of ethylene evolution started 130 days after bloom (DAB) at both elevations. During early ripening, fruits from LL trees produced significantly more ethylene than those from HL trees. Expression analysis of MdACS1, MdACO1 and MdERS1 indicated that the transcript accumulation well correlated with ethylene evolution. MdCTR1 was expressed at constant level throughout fruit growth and development up to 130 DAB, thereafter, the transcript accumulation decreased up to commercial harvest, concurrently with the onset of ethylene evolution. [source]

High-level bacterial cellulase accumulation in chloroplast-transformed tobacco mediated by downstream box fusions

Benjamin N. Gray
Abstract The Thermobifida fusca cel6A gene encoding an endoglucanase was fused to three different downstream box (DB) regions to generate cel6A genes with 14 amino acid fusions. The DB-Cel6A fusions were inserted into the tobacco (Nicotiana tabacum cv. Samsun) chloroplast genome for protein expression. Accumulation of Cel6A protein in transformed tobacco leaves varied over approximately two orders of magnitude, dependent on the identity of the DB region fused to the cel6A open reading frame (ORF). Additionally, the DB region fused to the cel6A ORF affected the accumulation of Cel6A protein in aging leaves, with the most effective DB regions allowing for high level accumulation of Cel6A protein in young, mature, and old leaves, while Cel6A protein accumulation decreased with leaf age when less effective DB regions were fused to the cel6A ORF. In the most highly expressed DB-Cel6A construct, enzymatically active Cel6A protein accumulated at up to 10.7% of total soluble leaf protein (%TSP). The strategy used for high-level endoglucanase expression may be useful for expression of other cellulolytic enzymes in chloroplasts, ultimately leading to cost-effective heterologous enzyme production for cellulosic ethanol using transplastomic plants. Biotechnol. Bioeng. 2009;102: 1045,1054. 2008 Wiley Periodicals, Inc. [source]