Sphagnum bleaching:Bicarbonate ‘toxicity’ and tolerance for seven Sphagnum species

Growth and functioning of Sphagnum mosses are closely linked to water level and chemistry. Sphagnum mosses occur in wet, generally acidic conditions, and when buffered, alkaline water is known to negatively impact Sphagnum. The effects of time, dose and species-specific responses of buffered, alkaline water on Sphagnum are largely unknown. We investigated the effects of bicarbonate and calcium on the survival, growth and physiological functioning of seven Sphagnum species occurring in contrasting environments, from raised bogs to (rich) fens. Mosses were submerged in different concentrations of bicarbonate and calcium solutions for 10 weeks under climate-controlled circumstances. After 2 weeks, all species exposed to the high bicarbonate treatment (2.0 mM) showed severe potassium leakage and swift discoloration. In contrast, species showed differential responses to the intermediate bicarbonate treatment (0.8 mM), some with a later onset of potassium leakage. S. squarrosum, S. teres & S. contortum generally persisted the longest, with all species dying after 6 to 10 weeks. Calcium alone, in contrast, negatively affected S. squarrosum, S. teres & S. contortum, causing discoloration and potassium leakage. Our study shows enrichment with bicarbonate, but not calcium, is detrimental for most Sphagnum species tested. A mechanistic model was developed that is consistent with dose and duration dependence and the species specificity. Future conservation and restoration measures for Sphagnum-dominated habitats and Sphagnum farming (cultivation, production and harvest of Sphagnum moss biomass) should limit flooding with bicarbonate-rich waters while investigating new management options, like acidifying surface waters to lower bicarbonate levels

Data from: Root and shoot glucosinolate allocation patterns follow optimal defence allocation theory

Item does not contain fulltext1. Optimal defence allocation theory (ODT) is one of the most prominent theoretical frameworks to explain the allocation of defence compounds within plants. It predicts that the most valuable and vulnerable plant organs have the highest levels of chemical defence. The ODT has been well worked out and experimentally tested for shoot defences, but not for root defences. To assess if ODT principles apply similarly to roots and shoots, we examined glucosinolates in aboveground and belowground organs of nine plant species belonging to two families. 2. In order to evaluate whether ODT equally applies to shoot and root organs, we designed a conceptual model in which aboveground and belowground organs were assigned to orders of importance to plant performance. We hypothesized that organs constituting the plant’s core structure are better protected than more distal organs. 3. The nine plant species were cultivated, and their roots and shoots were harvested and divided in three orders for glucosinolate analysis. Using a specialist (Delia radicum) and a generalist (Amphimallon solstitiale) root herbivore, we also experimentally tested the hypothesis that the generalist herbivore prefers to feed on fine roots with a low glucosinolate concentration, while the specialist prefers taproots with a high glucosinolate concentration. 4. We found that both in roots and shoots the higher-ordered core structural organs (taproots and stems) had the highest levels of glucosinolates. Belowground, taproots and lateral roots were better protected than the more distal, and less costly, fine roots in seven out of nine species tested. The specialist root herbivore preferred feeding on the highly defended taproots, which is in line with what has been found for aboveground specialist herbivores. Moreover, the glucosinolate concentration in roots overall was significantly higher than that in shoots. 5. Synthesis. These results support the hypothesis that ODT generally applies to glucosinolate allocation in aboveground and belowground organs and may mainly serve to maintain the integrity of the main plant structure. Moreover, it suggests that aboveground and belowground insect herbivores independently exert similar selection pressures on defence allocation patterns in roots and shoots.nul

Data from: Root and shoot glucosinolate allocation patterns follow optimal defence allocation theory

1. Optimal defence allocation theory (ODT) is one of the most prominent theoretical frameworks to explain the allocation of defence compounds within plants. It predicts that the most valuable and vulnerable plant organs have the highest levels of chemical defence. The ODT has been well worked out and experimentally tested for shoot defences, but not for root defences. To assess if ODT principles apply similarly to roots and shoots, we examined glucosinolates in aboveground and belowground organs of nine plant species belonging to two families. 2. In order to evaluate whether ODT equally applies to shoot and root organs, we designed a conceptual model in which aboveground and belowground organs were assigned to orders of importance to plant performance. We hypothesized that organs constituting the plant’s core structure are better protected than more distal organs. 3. The nine plant species were cultivated, and their roots and shoots were harvested and divided in three orders for glucosinolate analysis. Using a specialist (Delia radicum) and a generalist (Amphimallon solstitiale) root herbivore, we also experimentally tested the hypothesis that the generalist herbivore prefers to feed on fine roots with a low glucosinolate concentration, while the specialist prefers taproots with a high glucosinolate concentration. 4. We found that both in roots and shoots the higher-ordered core structural organs (taproots and stems) had the highest levels of glucosinolates. Belowground, taproots and lateral roots were better protected than the more distal, and less costly, fine roots in seven out of nine species tested. The specialist root herbivore preferred feeding on the highly defended taproots, which is in line with what has been found for aboveground specialist herbivores. Moreover, the glucosinolate concentration in roots overall was significantly higher than that in shoots. 5. Synthesis. These results support the hypothesis that ODT generally applies to glucosinolate allocation in aboveground and belowground organs and may mainly serve to maintain the integrity of the main plant structure. Moreover, it suggests that aboveground and belowground insect herbivores independently exert similar selection pressures on defence allocation patterns in roots and shoots

Root and shoot glucosinolate allocation patterns follow optimal defence allocation theory

Contains fulltext : 176861.pdf (publisher's version ) (Closed access

Effect of atmospheric carbon dioxide levels and nitrate fertilization on glucosinolate biosynthesis in mechanically damaged Arabidopsis plants

Contains fulltext : 161991.pdf (publisher's version ) (Open Access

Della proteins modulate arabidopsis defences induced in response to caterpillar herbivory

Contains fulltext : 128065pos.pdf (postprint version ) (Open Access

Isolation and identification of 4-alpha-rhamnosyloxy benzyl glucosinolate in noccaea caerulescens showing intraspecific variation

Contains fulltext : 144055pos.pdf (postprint version ) (Open Access

Social media en politiek: De waarheid achterhaald

Politici en burgers zijn massaal social media gaan gebruiken. Dit onderzoeksrapport is het vierde rapport in een reeks van onderzoeken naar de impact van social media op de Nederlandse verkiezingen, uitgevoerd door een onderzoeksteam van de kenniskring Nieuwe Media & Participatie van Saxion. Deze rapportage heeft betrekking op de Tweede Kamerverkiezingen van 12 september 2012 met de volgende vraagstelling: “In welke mate is er invloed waarneembaar van het gebruik van social media door verkiezingskandidaten op de hoeveelheid stemmen die zij krijgen bij de verkiezing van de leden van de Tweede Kamer van de Staten Generaal?” De onderzoeksgroep heeft gebruik gemaakt van de Social Media Indicator (SMI). Dit standaard meetinstrument is ontwikkeld ter voorbereiding op de verkiezingen van 2010 en inmiddels verder verfijnd en gevalideerd. Door dit meet-instrument opnieuw te gebruiken konden vergelijkbare resultaten verkregen worden. Er is een behoorlijke toename te zien in het social media gebruik onder vrijwel alle partijen sinds de vorige verkiezingen. Binnen vier partijen hebben actievere social media gebruikers ook relatief meer stemmen behaald. Bij één partij lijkt social media ten koste te gaan van stemmen. Bij de overige partijen was er geen effect zichtbaar. Opmerkelijk genoeg zijn de grote winnaars van de verkiezingen, VVD en PvdA, ook de grote winnaars ten aanzien van effectieve toepassing van social media.  Dit Saxion-onderzoek heeft aangetoond dat er nog steeds grote verschillen bestaan tussen de Nederlandse politieke partijen als het gaat om de effectiviteit van het social media beleid en de uitwerking op voorkeurstemmen van kandidaten

Adaptive Pitch Detection employing the use of Fast Fourier Transform and Autocorrelation Function

Contains fulltext : 144065.pdf (publisher's version ) (Open Access