Histochemical Study of Photoperiodic and Low Temperature Effects on Floral Induction of Spinacia oleracea

Shoot apices of Spinacia oleracea plants have been induced toflower either by: (a) subjecting leaves to 24 h long day, or(b) exposure to a short photoperiod but displaced by 8 h (displacedshort day) in the usual 24 h short-day cycle, or (c) exposureto low temperature (5 °C) during the dark period of thenormal short day. A quantitative cytochemical assay of pentosephosphate pathway activity during floral induction indicatesan approximate doubling of the rate of activity when comparedto that of vegetative apices (short day) (21 °C). Exposure to either low temperature, or a displaced short photoperiodstimulates pentose phosphate pathway activity in the shoot apexin a manner similar to that seen by long-day induction. Thischange in metabolic activity is accompanied by changes in theshape of the shoot apex which resembles that seen at an earlystage during floral induction. Spinacia oleracea, pentose phosphate pathway, shoot apex, glucose-6-phosphate dehydrogenase, floral induction, chilling, displaced short day     

Phenolics Composition and Biological Activities Assessment of Leaves,Flowers and Roots Extracts from Erodium glaucophyllum,Erodium hirtum and Erodium guttatum

Biology Bulletin - Erodium glaucophyllum, Erodium hirtum and Erodium guttatum were medicinal herbs from a southern Mediterranean known for its health benefits. There is a strong demand for the find...     

Should I stay or should I go?: Shedding of RPTPs in cancer cells switches signals from stabilizing cell-cell adhesion to driving cell migration

Dissolution of cell-cell adhesive contacts and increased cell-extracellular matrix adhesion are hallmarks of the migratory and invasive phenotype of cancer cells. These changes are facilitated by growth factor binding to receptor protein tyrosine kinases (RTKs). In normal cells, cell-cell adhesion molecules (CAMs), including some receptor protein tyrosine phosphatases (RPTPs), antagonize RTK signaling by promoting adhesion over migration. In cancer, RTK signaling is constitutive due to mutated or amplified RTKs, which leads to growth factor independence or autonomy. An alternative route for a tumor cell to achieve autonomy is to inactivate cell-cell CAMs such as RPTPs. RPTPs directly mediate cell adhesion and regulate both cadherin-dependent adhesion and signaling. In addition, RPTPs antagonize RTK signaling by dephosphorylating molecules activated following ligand binding. Both RPTPs and cadherins are downregulated in tumor cells by cleavage at the cell surface. This results in shedding of the extracellular, adhesive segment and displacement of the intracellular segment, altering its subcellular localization and access to substrates or binding partners. In this commentary we discuss the signals that are altered following RPTP and cadherin cleavage to promote cell migration. Tumor cells both step on the gas (RTKs) and disconnect the brakes (RPTPs and cadherins) during their invasive and metastatic journey.Key words: receptor protein tyrosine kinase, receptor-like protein tyrosine phosphatase, cadherins, cell adhesion, signal transduction, phospholipase C gamma, protein kinase C, catenins, IQGAP1 protein, regulated intramembrane proteolysis     

EFFECTS OF DIETARY SUPPLEMENTAL L-CARNITINE AND ASCORBIC ACID ON PERFORMANCE,CARCASS COMPOSITION AND PLASMA L-CARNITINE CONCENTRATION OF BROILER CHICKS REARED UNDER DIFFERENT TEMPERATURE

The present study was initiated to determine whether dietary supplemental L-carnitine and ascorbic acid affect growth performance, carcass yield and composition, abdominal fat and plasma L-carnitine concentration of broiler chicks reared under normal and high temperature. During the experiment, two temperature regimes were employed in two experimental rooms, which were identical but different in environmental temperature. The regimes were thermoneutral (20-22°C for 24 h) or recycling hot (34-36°C for 8 h and 20-22°C for 16 h). One-day-old broiler chicks (ROSS) were used in the experiment. A 2 x 2 x 2 factorial arrangement was employed with two levels (0 and 50 mg/kg) of supplemental L-carnitine and two levels (0 or 500 mg/kg) of supplemental ascorbic acid in drinking water under thermoneutral or high temperature regimes. Body weight gain was affected by high temperature. However, body weight gain was significantly improved in animals receiving supplemental L-carnitine, ascorbic acid or L-carnitine + ascorbic acid compared to animals receiving unsupplemented diet under high temperature. On the other hand, supplemental L-carnitine or L-carnitine + ascorbic acid reduced body weight gain under thermoneutral condition. Supplemental ascorbic acid significantly improved feed conversion efficiency, the improvement was relatively greater under high temperature. The L-carnitine content in the plasma was higher in the groups receiving supplemental L-carnitine and ascorbic acid under high temperature, while broilers fed supplemental L-carnitine and ascorbic acid had a decreased level of plasma L-carnitine concentration under normal temperature. It is concluded that dietary supplemental L-carnitine or L-carnitine + ascorbic acid may have positive effects on body weight gain, carcass weight under high temperature conditions.     

Phytodiversity of temperate permanent grasslands: ecosystem services for agriculture and livestock management for diversity conservation

Plant diversity has been reported to increase productivity. Farming practices aiming at conserving or increasing plant diversity are, however, usually less profitable than conventional ones. In this review, we aim to find reasons for this discrepancy, discuss ecosystem services of grassland phytodiversity that are useful for farmers, and ways of livestock management most beneficial for diversity. Under agricultural conditions, a clear effect of species richness on a site’s primary or secondary production has not yet been demonstrated. Reasons could be that species numbers in permanent grassland are above the threshold of five species found effective in experimental plots or that the conditions are more in equilibrium with management than in weeded experimental plots. Other diversity effects on production stability, nutrient and water retention or product quality might convince farmers to increase diversity. However, these should be tested in agricultural situations, as most research has again been carried out in experimental plots. To enhance phytodiversity, grazing has been found superior over mowing, as selective grazing, treading and excreta deposition increase the heterogeneity of a sward and thus the niches available. Especially rotational grazing with intermediate intensity may be advantageous for phytodiversity. However, complex interactions between environmental conditions, sward composition, management and livestock behaviour make it difficult to forecast grazing effects. Thus, ecological and agricultural researchers should cooperate more, e.g. either in interdisciplinary projects or by hiring researchers from the respective other profession and thus diversifying research groups, in order to integrate agricultural management into biodiversity research and biodiversity measurements into agricultural research to advance our understanding of how to make conservation and enhancement of grassland phytodiversity both feasible and sustainable.     

Manipulating the species composition of permanent grasslands—A new approach to biodiversity experiments

The relationship between biodiversity and ecosystem functions of grasslands has received increasing attention in recent years. So far, experiments were mostly conducted in experimental grasslands. We used a different approach on permanent grassland by applying herbicides selective against either dicots or monocots. This allowed us to alter plant species composition and evenness and to obtain altered constellations of functional group abundances without deliberate introduction of new species or continued disturbance by weeding. The resulting swards were subjected to different management intensities in terms of cutting regime and fertilization. Compared to the baseline data before herbicide application, within one year, the combination of treatments, especially the herbicide application, led to a broad variety of swards with the herbicide treatment alone accounting for more than 25% of the variance in composition. We conclude that the application of specific herbicides is a method highly suitable for creating different sward types, because the swards differed significantly in species number, evenness and composition of functional groups without showing signs of disturbance, as neither the area of open soil nor the proportion of annual colonizer species increased.     

The provision of supplementary fresh water improves the breeding success of the globally threatened Northern Bald Ibis Geronticus eremita

The Northern Bald Ibis Geronticus eremita is a globally threatened species with its main remaining world population breeding in an area of sea cliffs and coastal semi‐desert steppe near Agadir in southern Morocco. Between 1998 and 2002, we showed experimentally that the small‐scale provision of fresh water near the breeding colonies led to an increase in the productivity of the birds. The increase was greatest in years with low natural rainfall but was positive in all years tested. The supplementary fresh water appears to help buffer productivity against the impacts of low rainfall and its provision is now part of the ongoing conservation measures for this species.