Pootgoedvermeerdering zetmeelaardappelen

In opdracht van Productschap Akkerbouw is onderzoek gedaan naar éénjarige rasvermeerdering van (TBM)-pootgoed. Afhankelijk van het perspectief van een ras voor de zetmeelteelt en de beschikbaarheid van pootgoed bij de kweekbedrijven, is er elk jaar in de periode 2008 tot en met 2012 een rasvermeerdering met verschillende rassen aangelegd op de PPO-locaties Kooijenburg of ‘t Kompas. Van deze rassen zijn in elk jaar de opbrengsten en aantal knollen per sortering bepaald en de vermeerderingsfactor t.b.v. areaalplanning en pootafstand berekend. In het veld zijn de bacteriezieke planten en de viruszieke planten geteld en verwijderd

A very brief description of LOFAR - the Low Frequency Array

LOFAR (Low Frequency Array) is an innovative radio telescope optimized for the frequency range 30-240 MHz. The telescope is realized as a phased aperture array without any moving parts. Digital beam forming allows the telescope to point to any part of the sky within a second. Transient buffering makes retrospective imaging of explosive short-term events possible. The scientific focus of LOFAR will initially be on four key science projects (KSPs): 1) detection of the formation of the very first stars and galaxies in the universe during the so-called epoch of reionization by measuring the power spectrum of the neutral hydrogen 21-cm line (Shaver et al. 1999) on the ~5' scale; 2) low-frequency surveys of the sky with of order $10^8$ expected new sources; 3) all-sky monitoring and detection of transient radio sources such as gamma-ray bursts, x-ray binaries, and exo-planets (Farrell et al. 2004); and 4) radio detection of ultra-high energy cosmic rays and neutrinos (Falcke & Gorham 2003) allowing for the first time access to particles beyond 10^21 eV (Scholten et al. 2006). Apart from the KSPs open access for smaller projects is also planned. Here we give a brief description of the telescope.Comment: 2 pages, IAU GA 2006, Highlights of Astronomy, Volume 14, K.A. van der Hucht, e

Pootgoedvermeerdering zetmeelaardappelen

In opdracht van Productschap Akkerbouw is onderzoek gedaan naar éénjarige rasvermeerdering van (TBM)-pootgoed. Afhankelijk van het perspectief van een ras voor de zetmeelteelt en de beschikbaarheid van pootgoed bij de kweekbedrijven, is er elk jaar in de periode 2008 tot en met 2012 een rasvermeerdering met verschillende rassen aangelegd op de PPO-locaties Kooijenburg of ‘t Kompas. Van deze rassen zijn in elk jaar de opbrengsten en aantal knollen per sortering bepaald en de vermeerderingsfactor t.b.v. areaalplanning en pootafstand berekend. In het veld zijn de bacteriezieke planten en de viruszieke planten geteld en verwijderd

HPLC analysis of nonprotein thiols in planktonic diatoms: Pool size, redox state and response to copper and cadmium exposure

A sensitive method was developed to analyze low molecular weight thiols involved in metal homeostasis and detoxification in phytoplankton. The aims of this study were to (1) separate and measure all relevant thiols in a single HPLC run; (2) measure redox states of the thiols and (3) identify specific responses of thiols (pools, redox) to heavy metals by testing diatoms with different metal tolerances (Ditylum brightwellii, Phaeodactylum tricornutum, Skeletonema costatum and Thalassiosira pseudonana). Copper or cadmium were dosed at a maximum tolerable, species-dependent level, to exponential phase cells growing in artifical medium (14 parts per thousand, salinity). Loss of cell viability was monitored by the decrease of fluorescein fluorescence after a 24-h metal exposure. Thiols in extracts of exposed cells and controls were labeled with monobromobimane. Picomoles of cysteine, glutathione, gamma- glutamylcysteine and phytochelatins (PCs) were detected and separated by reversed-phase high performance liquid chromatography. Cysteine increased in all species after metal exposure. The species with the largest glutathione pools in the control (P. tricornutum) synthesized the largest PC pools upon metal exposure, however, at a similar to 40% ro loss of glutathione. A considerable increase of glutathione was observed in D. brightwellii upon metal exposure. However, it produced little PC (and only with Cu). In controls (similar to 3 pM Cu2+), PC2 was detectable in S. costatum, P. tricornutum and T. pseudonana. Oxidized thiol fractions were recovered by the reductants DTT and TCEP, both performing identically. Compared to the other thiols, cysteine had low redox ratios. In D. brightwellii glutathione and PC redox ratios were lower than in P. tricornutum, S. costatum and T. pseudonana. It was expected that Cu-induced oxidative stress would decrease the thiol redox ratios, however, this was not observed. [KEYWORDS: Performance liquid-chromatography; phytochelatin production; ditylum-brightwellii; marine diatom; binding polypeptides; metabolic-activity; oxidative stress; silene-vulgaris; maize seedlings; heavy-metals]

Effect of the nitrogen status on copper accumulation and pools of metal-binding peptides in the planktonic diatom Thalassiosira pseudonana

Effects of the algal cellular nitrogen status on the defence against copper toxicity were studied in batch cultures of the coastal diatom Thalassiosira pseudonana, grown in coastal seawater (Oosterschelde, SW Netherlands; 30 parts per thousand salinity). The media represented nutrient-poor (summer) and nutrient-rich (winter) conditions, both without and with additional nitrate, respectively. In the summer series, initial inorganic N:P ratios were 1.5 and 7.1. In the winter series, N:P ratios were 12.2 and 18.4. Cu was added at five levels (0- 315 nM). We expected a low cellular nitrogen status to limit the synthesis of metal-binding peptides (phytochelatins). In N- enriched summer media phytochelatins were detectable (HPLC) only at the upper Cu level. In N-enriched winter media phytochelatins were detectable (14.6 mu M SH) even without additional Cu (pCu similar to 14; pZn similar to 8), whilst in low-nitrate winter media, phytochelatins were induced at somewhat higher Cu additions; cellular Cu concentrations were similar in both cases (similar to 25 mu M). In general, cells accumulated more Cu, Mn and Zn (summer and winter series) in N- enriched media, compared to low-nitrate media. In the low N:P media (summer) division rates were hardly affected by Cu. At N:P 12.2 and N:P 18.4, at cellular metal levels identical to those in low N:P media. T. pseudonana proved to be more Cu sensitive. In these nitrogen-rich winter conditions, phosphorus deficiency could have played a role. It was discussed that a P limitation might result in an impaired exclusion/export of copper. Phytochelatins appeared in T. pseudonana at cellular atomic C:N ratios lower than similar to 15, and at ambient inorganic N:P ratios higher than the Redfield ratio (similar to 16). Phytochelatins indicate metal toxicity (sensitivity) rather than available metal concentrations in the coastal marine environment, and will not be detectable at natural background concentrations of Cu and Zn under a nitrogen limitation. [KEYWORDS: C : N ratio; copper; detoxification; diatom; glutathione; phytochelatin Ditylum-brightwellii; chemical speciation; nutrient limitation; silene-vulgaris; maize seedlings; hplc analysis; heavy-metals;cadmium; toxicity; zinc]