The reaction of phloroglucinol in the presence of acid with lignin-containing materials

The employment of a removable chitosan-derivatized polymeric sensitizer in the photooxidation of polyhydroxylated water-pollutants

The known O2((1)∆g)-sensitizer system Chitosan bounded Rose Bengal (CH-RB), with Rose Bengal (RB) immobilized by irreversible covalent bonding to the polymer Chitosan (CH), soluble in aquous acidic medium, was employed in the photodegradation of three tri-hydroxy benzene water-contaminants (THBs). The system sensitizes the O2((1)∆g)-mediated photodegradation of THBs by a process kinetically favored, as compared to that employing free RB dissolved in the same solvent. Additionally the free xanthene dye, degradable by O2((1)∆g) through self-sensitization upon prolonged light-exposure, is considerably protected when bonded to CH-polymer. The polymeric sensitizer, totally insoluble in neutral medium, can be removed from the solution after the photodegradative cycle by precipitation through a simple pH change. This fact constitutes an interesting aspect in the context of photoremediation of confined polluted waters. In other words, the sensitizing system could be useful for avoiding to dissolve dyestuffs in the polluted waters, in order to act as conventional sunlight-absorbing dye-sensitizers. In parallel the interaction CH-O2((1)∆g) in acidic solution was evaluated. The polymer quenches the oxidative species with a rate constant 2.4 × 10(8) M(-1) s(-1) being the process mostly attributable to a physical interaction. This fact promotes the photoprotection of the bonded dye in the CH-RB polymer.

Impact of hydrothermal pre-treatment to chemical composition, enzymatic digestibility and spatial distribution of cell wall polymers

The effect of hydrothermal pretreatment on chemical composition, microscopic structure and enzymatic digestibility of wheat straw was studied. Wheat straw was pretreated with increasing severity to obtain series of samples with altered chemistry and structure. The hydrothermal pretreatment caused solubilisation of arabinoxylan and phenolic acids and their dimers in a temperature dependent manner with minor effects on the cellulose and Klason lignin content. In the cell wall level, the pretreatment intensified staining of cellulose and relocalised xylan in the cell walls. The distribution, properties and content of the cell wall phenolic compounds was altered as observed with phloroglucinol and autofluorescence imaging. In the enzymatic hydrolysis, the highest yields were obtained from the samples with a low xylan and diferulate content. On the cell wall structural level, the sample with the highest digestibility was observed to have intensified cellulose staining, possibly reflecting the increased accessibility of cellulose.

Cellulolytic environment in the midgut of the wood-feeding higher termite Nasutitermes takasagoensis

Unlike lower termites, xylophagous higher termites thrive on wood without the aid of symbiotic protists. In the higher termite Nasutitermes takasagoensis, both endogenous endo-β-1,4-glucanase and β-glucosidase genes are expressed in the midgut, which is believed to be the main site of cellulose digestion. To further explore the detailed cellulolytic system in the midgut of N. takasagoensis, we performed immunohistochemistry and digital light microscopy to determine distributions of cellulolytic enzymes in the salivary glands and the midgut as well as the total cellulolytic activity in the midgut. Although cellulolytic enzymes were uniformly produced in the midgut epithelium, the concentration of endo-β-1,4-glucanase activity and luminal volume in the midgut were comparable to those of the wood-feeding lower termite Coptotermes formosanus, which digests cellulose with the aid of hindgut protists. However, the size of ingested wood particles was considerably larger in N. takasagoensis than that in C. formosanus. Nevertheless, it is possible that the cellulolytic system in the midgut of N. takasagoensis hydrolyzes highly crystalline cellulose to a certain extent. The glucose produced did not accumulate in the midgut lumen. Therefore, the present study suggests that the midgut of the higher termite provides the necessary conditions for cellulolysis.

Role of leaf glandular trichomes of melon plants in deterrence of Aphis gossypii Glover

External characteristics of the leaf epidermis and their effects on behaviour of Aphis gossypii Glover were evaluated in two Cucumis melo L. genotypes, 'Bola de Oro' (aphid susceptible) and TGR-1551 (aphid resistant) in order to explore their role in the early rejection of TGR-1551 by this aphid. No differential effects of epicuticular waxes on aphid behaviour were observed. The type, distribution and number of trichomes on melon leaves were also studied. Pubescence in melon, measured as the number of non-glandular trichomes per cm(2), was not sufficient to prevent aphid settling. However, there was a high density of type I glandular trichomes on leaves of the aphid-resistant genotype. According to microscopic observations and stain testing, these trichomes store and secrete phenols and flavonoids. Free-choice tests were conducted to determine the effect of these glandular trichomes on A. gossypii preference, revealing that aphids reject leaf disks of TGR-1551 from the onset of the experiment. Additional experiments after removal of leaf type I glandular trichome exudates showed that A. gossypii preferred washed TGR-1551 leaf disks over unwashed disks, while this effect was not observed in experiments using washed and unwashed 'Bola de Oro' leaf disks. These results suggest that a high density of glandular trichomes and chemicals secreted by them deter A. gossypii and disturb aphid settling on TGR-1551.

Hypersensitive response to Aphis gossypii Glover in melon genotypes carrying the Vat gene

Aphis gossypii Glover causes direct and indirect damage to Cucumis melo L. crops. To decrease the harmful effects of this pest, one of the most economically and environmentally acceptable options is to use genetically resistant melon varieties. To date, several sources of resistance carrying the Vat gene are used in melon breeding programmes that aim to prevent A. gossypii colonization and the subsequent aphid virus transmission. The results suggest that the resistance conferred by this gene is associated with a microscopic hypersensitive response specific against A. gossypii. Soon after aphid infestation, phenol synthesis, deposits of callose and lignin in the cell walls, damage to the plasmalemma, and a micro-oxidative burst were detected in genotypes carrying the Vat gene. According to electrical penetration graph experiments, this response seems to occur after aphid stylets puncture the plant cells and not during intercellular stylet penetration. This type of plant tissue reaction was not detected in melon plants infested with Bemisia tabaci Gennadius nor Myzus persicae Sulzer.