Search Results (4)

Alkaline pretreatments are considered highly effective for the separation of the different components of lignocellulosic biomass. However, cold alkaline extraction (CAE) exhibits minimal modification/degradation of hemicellulosic fraction and successfully accomplishes efficient delignification. In this research, the fast-growing clone AF2 of Populus x euramericana wood was utilized as the raw material and subjected to ultrasound-assisted CAE. The objective of incorporating ultrasound into cold alkaline extraction is to increase the yield of a hemicellulosic-rich liquid phase that can be used to produce high-value products such as furfural or xylitol. Simultaneously, it aims to obtain a solid phase with a higher calorific value compared to the raw material. The results, obtained from a central composite factorial design, demonstrated that the CAE process for 90 min at a sodium hydroxide concentration of 100 g L⁻¹, a temperature of 30 °C, and with ultrasound assistance maximized hemicellulose extraction in the liquid phase (60.8% was extracted) and improved the heating value of solid phase. Full article

Sexually dimorphic response to stress has been observed in assorted natural dioecious plants. Up to now, few studies have focused on the difference of stress responses between artificially bred siblings. To determine the sexual dimorphism between artificially bred sibling poplar trees, we conducted a study comparing the response to water deficit between male and female Populus × euramericana siblings. This pair of hybrids was analyzed in terms of growth, photosynthesis, membrane injury and repair systems, as well as gene regulation patterns. The female and male siblings presented distinct responses to water deficit, with greater inhibition in females’ growth and photosynthesis. The results also displayed that in females, relative electrolyte leakage and malonaldehyde content were higher than those in males under water deficit conditions. On the other hand, water deficit caused a greater increase in both SOD activity and POD activity in males than those in females. Consistent with these physiological differences, the expression of several stress-related genes, including SOD, GST, bHLH35, and PsbX1, was regulated differently between female and male hybrids by water deficit stress. Higher expression of SOD in moderate-water-deficit-treated females and higher GST, bHLH35 expression in both moderate- and severe-water-deficit-treated females suggest that the female sib is more sensitive, whilst higher expression of SOD in severe-water-deficit-treated males and higher PsbX1 expression in water-deficit-treated males testify that males protect cells better. To achieve an integrated view, all these variables were analyzed through the use of a principal component analysis and a total discrepancy between the sexes in their response to water deficit was demonstrated. The results indicate that, compared with male poplar sibs, females are more sensitive, but deploy a weaker protective apparatus to deal with water deficit. Full article

Halomorphic soils cover a significant area in the Vojvodina region and represent ecological and economic challenges for agricultural and forestry sectors. In this study, four economically important Serbian poplar clones were compared according to their biochemical and transcriptomic responses towards mild and severe salt stress to select the most tolerant clones for afforestation of halomorphic soils. Three prospective clones of Populus deltoides (Bora-B229, Antonije-182/81 and PE19/66) and one of hybrid genetic background P. nigraxP. deltoides, e.g., P. x euramericana (Pannonia-M1) were hydroponically subjected to NaCl as a salt stress agent in a concentration range from 150 mM to 450 mM. Plant responses were measured at different time periods in the leaves. Biochemical response of poplar clones to salt stress was estimated by tracking several parameters such as different radical scavenging capacities (estimated by DPPH, FRAP and ABTS assays), accumulation of total phenolic content and flavonoids. Furthermore, accumulation of two osmolytes, glycine betaine and proline, were quantified. The genetic difference of those clones has been already shown by single nucleotide polymorphisms (SNPs) but this paper emphasized their differences regarding biochemical and transcriptomic salt stress responses. Five candidate genes, two putative poplar homologues of GRAS family TFs (PtGRAS17 and PtGRAS16), PtDREB2 of DREB family TFs and two abiotic stress-inducible genes (PtP5SC1, PtSOS1), were examined for their expression profiles. Results show that most salt stress-responsive genes were induced in clones M1 and PE19/66, thus showing they can tolerate salt environments with high concentrations and could be efficient in phytoremediation of salt environments. Clone M1 and PE19/66 has ABA-dependent mechanisms expressing the PtP5CS1 gene while clone 182/81 could regulate the expression of the same gene by ABA-independent pathway. To improve salt tolerance in poplar, two putative GRAS/SCL TFs and PtDREB2 gene seem to be promising candidates for genetic engineering of salt-tolerant poplar clones. Full article

Riparian vegetation, which performs many key ecological functions, has been modified or lost at an alarming rate during the past century as a result of human activity. The aims of this study are (a) to investigate the effects of poplar plantations on plant diversity in riparian zones; and (b) to estimate the ecological implications of extending cover by poplar plantations. For this purpose, we assessed species richness, habitat indicator species and functional diversity based on Grime’s C-S-R strategies. We used non-metric multidimensional scaling to examine the role of environmental factors such as soil properties, forest structure and management. Disturbance, in particular the frequency of harrowing, led to a decline in species richness and modified the indicator species and functional diversity by favoring Ruderal (R) species at the expense Stress-Tolerant (S) and Competitor (C) species, which are better suited to riparian forest conditions. Poplar plantations should not be used as surrogates for riparian forests, and minimizing harrowing in poplar plantations promotes vascular plant diversity. Furthermore, reintroduction of herbs, ferns and geophytes with a high conservation value and low seed dispersal capacity is advisable from the sixth year after establishment, once harrowing for weed control has been completed. Full article