Populus Euphratica Research Articles

Pseudomonas lopnurensis sp. nov., an endophytic bacterium isolated from Populus euphratica at the ancient Ugan river

A Gram-stain negative, aerobic, rod-shaped, motile by a single polar flagellum, non-spore-forming bacterium, designated strain AL-54T, was isolated from the storage liquid in the stems of Populus euphratica tree at the ancient Ugan River in Xinjiang, PR China. Isolated AL-54T grew optimally at pH 7.0 and temperature 35°C in the presence of 3% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence demonstrated that the isolate belonged to the genus Pseudomonas and was closely related to Pseudomonas songnenensis NEAU-ST5-5 T (97.6%), Pseudomonas zhaodongensis NEAU-ST5-21 T (97.5%), Pseudomonas alcaliphila AL15-21T (97.3%), Pseudomonas toyotomiensis HT-3T (97.3%), Pseudomonas oleovorans subsp. lubricantis RS1T (97.3%), Pseudomonas stutzeri ATCC 17588T (97.3%), Pseudomonas chengduensis CGMCC 2318T (97.2%), and Pseudomonas xanthomarina KMM 1447T (97.1%). Multilocus Sequences Analysis (MLSA) of strain AL-54T based on the three housekeeping genes, rpoB, rpoD and gyrB further confirmed the phylogenetic assignment of the isolates. The G+C content was 64.7 mol%. The DNA-DNA hybridization with P. songnenensis NEAU-ST5-5 T, P. zhaodongensis NEAU-ST5-21T, P. alcaliphila AL15-21T, P. toyotomiensis HT-3T, P. oleovorans subsp. lubricantis RS1T, P. stutzeri ATCC 17588T, P. chengduensis CGMCC 2318T and P. xanthomarina KMM 1447T revealed 44.0%, 44.7%, 60.1%, 48.7%, 49.1%, 60.1%, 58.9% and 60.2% relatedness respectively. The predominant quinone system is ubiquinone-9 (Q-9). The major components of the cellular fatty acids (>10%) were summed feature 8 (comprising C18:1 ω7c /C18:1 ω6c), summed feature 3 (comprising C16:1 ω7c /C16:1 ω6c) and C16:0. The detected major polar lipids were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and phosphatidylcholine (PC). On the basis of phenotypic data, chemotaxonomic and phylogenetic properties, strain AL-54T can consider as a novel species within the genus Pseudomonas, for which the name Pseudomonas lopnurensis sp. nov. is proposed. The type strain is AL-54T (= JCM 19136T = CCTCC AB 2013066T = NRRL B-59987T).

Molecular cloning and characterization of a novel gene MsKMS1 in Medicago sativa

Vacuole membrane proteins play a critical role in the regulation of plant physiological processes including normal growth and development, and responses to stresses. The killing me slowly 1 (KMS1) gene that encodes a soluble N-ethylmaleimide-sensitive fusion attachment receptor (SNARE) domain-containing vacuole membrane protein was first reported in Arabidopsis. Currently, the function of KMS1 in other plants under stress is poorly understood. In this study, we report cloning, expression, and characterization of a novel KMS1 gene in alfalfa (Medicago sativa L.), designated MsKMS1 (GenBank accession No. JX467688). The full-length cDNA of MsKMS1 was 1 396 bp and contained a complete open reading frame of 1 257 bp, which encoded a putative protein of 418 amino acids. The BLASTp analysis showed that MsKMS1 shared high amino acid sequence similarities with KMS1 from other plants such as Medicago truncatula (99 %), Cicer arietinum (89 %), Glycine max (77 %), Prunus mume (76 %), Ricinus communis (72 %), Populus euphratica (72 %), Theobroma cacao (72 %), and Arabidopsis thaliana (67 %). Transient transformation of onion (Allium cepa) bulb scale epidermal cells by biolistic bombardment showed that MsKMS1 was localized to the plasma membrane. Quantitative real-time PCR revealed that MsKMS1 expression was upregulated under different abiotic stresses (200 mM NaCl, 20 % (m/v) polyethylene glycol 6000] and 10 mg dm-3 abscisic acid. Transgenic tobacco plants were obtained via Agrobacterium-mediated transformation and treated with 200 mM NaCl. Reverse-transcription PCR data showed that MsKMS1 was successfully transcribed and expressed in the leaves of transgenic plants. The MsKMS1-overexpressors showed a lower malondialdehyde content and maintained a higher relative water content and proline content compared with non-transgenic controls under salt stress. These results indicate that the introduction of the MsKMS1 gene could improve salt stress resistance in tobacco plants. This study reveals the role of MsKMS1 in the regulation of plant responses to abiotic stress and provides evidence for further functional studies of the KMS1 family in alfalfa.

Remote sensing image description based on word embedding and end-to-end deep learning

This study proposes an end-to-end image description generation model based on word embedding technology to realise the classification and identification of Populus euphratica and Tamarix in complex remote sensing images by providing descriptions in precise and concise natural sentences. First, category ambiguity over large-scale regions in remote sensing images is addressed by introducing the co-occurrence matrix and global vectors for word representation to generate the word vector features of the object to be identified. Second, a new multi-level end-to-end model is employed to further describe the content of remote sensing images and to better advance the description tasks for P. euphratica and Tamarix in remote sensing images. Experimental results reveal that the natural language sentences generated using this method can better describe P. euphratica and Tamarix in remote sensing images compared with conventional deep learning methods.

Complete chloroplast genome sequence of Populus euphratica from PacBio Sequel platform

Populus euphratica Oliv., one of tall arbors growing in desert areas, has great stress resistance. The complete chloroplast genome was reported in this study using the PacBio Sequel Platform. The chloroplast genome with a total size of 157,881 bp consisted of two inverted repeats (IRs) (27,666 bp) separated by a large single-copy region (85,906 bp) and a small single-copy region (16,643 bp). Further annotation revealed the chloroplast genome contains 111 genes, including 77 protein-coding genes, 30 tRNA genes, and four rRNA genes. The information of the chloroplast genome will be useful for study on the evolution of P. euphratica in the future.

Using Sentinel-2 Images to Map the Populus euphratica Distribution Based on the Spectral Difference Acquired at the Key Phenological Stage

Populus euphratica is an important tree species in desert ecosystems. The protection and restoration of natural Populus euphratica forests requires accurate positioning information. The use of Sentinel-2 images to map the Populus euphratica distribution at a large scale faces challenges associated with discriminating between Populus euphratica and Tamarix chinensis. To address this problem, this study selected the Daliyabuyi Oasis in the hinterland of the Taklimakan Desert as the study site and sought to distinguish Populus euphratica from Tamarix chinensis. First, we determined the peak spectral difference period (optimal time window) between Populus euphratica and Tamarix chinensis within monthly Sentinel-2 time-series images. Then, an appropriate vegetation index was selected to represent the spectral difference between Populus euphratica and Tamarix chinensis within the key phenological stage. Finally, the maximum entropy method was used to automatically determine the threshold to map the Populus euphratica distribution. The results indicated that the period from 22 April to 1 May was the optimal time window for mapping the Populus euphratica distribution in the Daliyabuyi Oasis. The combination of the inverted red-edge chlorophyll index (IRECI) and the maximum entropy method can effectively distinguish Populus euphratica from Tamarix chinensis. The user’s accuracy of the Populus euphratica distribution extraction from single-data Sentinel-2 images acquired within the optimal time window was 0.83, the producer’s accuracy was 0.72, and the F1-score was 0.77. This study verified the feasibility of mapping Populus euphratica distribution based on Sentinel-2 images, and analyzed the validity of exploiting spectral differences within the key phenological stage from a single-data image to distinguish between the two species. The results can be used to extract the distribution of Populus euphratica and serve as an auxiliary variable for other plant classification methods, providing a reference for the extraction and classification of desert plants.

The brassinosteroid biosynthesis enzyme gene PeCPD improves plant growth and salt tolerance in Populus tomentosa

A major challenge in the development of novel industrial woody crops lies in the trade-offs underlying plant growth, wood quality and abiotic stress tolerance. Single gene modifications in perennial species often lead to improvements in only one of these three processes. However, brassinosteroids (BRs) affect these three aspects, thus a BRs biosynthesis enzyme gene, PeCPD (Populus euphratica Oliv. Constitutive Photomorphogenenic Dwarf), was selected for this goal. PeCPD was mainly expressed in stems and leaves, and showed rapid responses to salt treatment. Plant height and biomass were improved in the PeCPD overexpressed lines, which was accompanied by the promotion of xylem differentiation and the reduction of pith size, consequently improving timber quality, relative to the wild type Populus tomentosa Carr. The transgenic lines also showed higher salt tolerance relative to the wild type, as indicated by less visual injuries and lower reactive oxygen species pressure. This was partly due to increased levels of soluble protein as well as higher superoxide dismutase (SOD) activity and proline level. Our results demonstrated the PeCPD overexpression mediates the trade-off between growth and abiotic stress adaptation in woody plants. The PeCPD overexpression modified the gene expression of BRs biosynthesis and metabolic process, which enhanced BRs response as indicated by improved transcript level of BRs signaling component. Our results showed that modifying PeCPD has a great potential for jointly improving growth, timber quality and abiotic stress tolerance in woody plants.

Revealing interactions between root phenolic metabolomes and rhizosphere bacterial communities in Populus euphratica plantations

How the root metabolic profiles and rhizosphere bacterial communities of dioecious plants respond to soil properties and sex identity is largely unknown. In this study, we analyzed root phenolic metabolomes and rhizosphere bacterial microbiomes of Populus euphratica females and males in two P. euphratica plantations with different soil properties to reveal the relative importance of soil and sex effects, and to decipher associations of certain phenolic compounds with specific bacterial taxa. We found that the relative abundances of bacterial OTUs and phenolic metabolites were closely linked to soil properties and sex identity. Soil is the main filter influencing the root phenolic metabolic profiles and rhizosphere bacterial communities of P. euphratica, while sexes and their interactions with soil properties are secondary factors. Differences in the diversity and evenness of phenolic metabolites were affected by plant sex, but not by soil properties. Conversely, the diversity and evenness of bacterial communities were affected by soil properties independent of plant sex. A multiple regression model indicated the presence of associations between root phenolic metabolites and specific soil bacteria taxa. Furthermore, all bacterial phyla and families correlated with at least one phenolic metabolite. Especially, both Nitrosomonadaceae and Cytophagaceae positively correlated with salicylic acid. Thus, our study provides new insights into the ecological mechanism that maintains rhizosphere bacterial communities in P. euphratica plantations in the desert area.

Anti-oral Cancer Biological Activity Evaluation and Chloroplast Genome Analyses of Populus euphratica.

In this research, the anti-cancer activity of the Populus euphratica extract was evaluated with Cell Counting Kit-8 (CCK-8) assay. The inhibitory activity of the Populus euphratica extract on the activation levels of VEGF signaling pathway in the cancer cells was measured with real time RT-PCR. Next, the high-throughput Illumina pair-end sequencing was performed to detect the chloroplast (cp) genome of Populus euphratica for genome evolution assessment. The CCK-8 results indicated that the extract of Populus euphratica exhibited the significantly suppression effect on the viability of the cancer cells, and the data of the real time RT-PCR showed the activation levels of VEGF signaling pathway in the cancer cells was also reduced obviously by the Populus euphratica extract. The circular cp genome of the Populus euphratica is 157,806 bp, encoding 131 genes, containing 8 Ribosomal RNA genes (rRNAs), 37 Transfer RNA genes (tRNAs) and 86 Protein coding genes (PCGs). And the results of the phylogenetic analysis indicated that the Populus euphratica. Furthermore, phylogenetic analysis revealed that Populus euphratica has the closest relationship with Populus pruinosa. In addition to Populus pruinosa, Populus ilicifolia also has closely relationship with Populus euphratica. These three species could be clustered on the same clade.

塔里木河上游荒漠河岸胡杨林树洞型空心树发生过程与形成机制

空心树是森林生态系统的重要组成部分，它在维系森林生态系统的动物或微生物多样性方面起着重要作用，但树木空心的发生过程和形成机制仍是一个悬而未决的科学问题。通过野外实调，解析了塔里木河上游肖夹克荒漠林区胡杨树洞型空心树数量特征、类型与分布格局，探讨了空心树的发生与形成过程。结果表明：1）胡杨幼林空心树发生频率较低，为10.34%，但成熟林空心树发生频率达到了83.78%；2）空心树树洞分为主干型和分枝型两大类，其中主干和分枝断口造成树洞是树洞型空心树形成的两种主要表现方式，分别占树洞类型的41.94%和19.35%；3）推断树洞发生过程为"外伤-分泌物外泄-木质部被腐蚀、消融-伤口扩大-形成树洞"；4）树木发生外伤的主要起因可能为长期的风沙侵扰，造成树木小枝或者分枝折断。;Hollow-bearing tree is a part of forest ecosystem, which plays an important role for maintaining species diversity of animals and microorganisms in forest. However, occurrence process and formation mechanism of hollow-bearing trees are still outstanding. As the main constructive species of desert riparian forest, Populus euphratica has importantly ecological significance in ecological balance maintenance, desertification control, biodiversity protection and natural protection of oasis ecosystem. In this study, the quantitative characteristics and distribution pattern of hollow-bearing trees of Populus euphratica in the desert riparian forest in the upper reaches of Tarim River were studied through field investigation and statistical analysis. We set up a sample plot of 30×200 m in young Populus euphratica forest and mature Populus euphratica forest, respectively. A total of 996 Populus euphratica trees were investigated, including 892 young trees and 104 mature trees. The hollow-bearing tree was defined that there was at least one visible hole with the diameter ≥ 5 cm. For the holes lower apart from the ground, we directly measured the length and width of the holes with a ruler; for the holes distributed at the high trunk or branches, we estimated the size of the holes with a telescope (10×25). The distance from the ground, the position in the trees, hole orientation, and the number of holes, as well as the diameter at breast height (DBH) of each tree was recorded when the field investigation was conducted. Based on the field investigation results, the types, occurrence process of hollows of Populus euphratica were discussed. The results showed that:1) the occurrence frequency of hollow-bearing tree in young Populus euphratica forest was relatively low (10.34%), but that of mature forest was very high, which was up to 83.78%. 2) Hollow-bearing trees could be divided into two categories:hollows in main stems and hollows in branches, in which hollows in twigs of main stem or hollows in branches of trees accounted for 41.94% and 19.35% of all the hollows, respectively. 3) The formation process of tree hollows might be injury-nutrients and moisture discharge-rotten of xylem and phloem-expansion of the wound-hollows formation. 4) The long-term wind and sand invasion was the possibly main driver of these injuries, which broke the twigs and branches of trees to form the injuries.

Genome-wide identification and analysis of monolignol biosynthesis genes in <i>Salix matsudana</i> Koidz and their relationship to accelerated growth

Lignin plays an important role in plant growth and development. It serves as a raw material for the manufacture of paper, animal feed, and chemical fertilizers. However, the regulation of lignin biosynthesis genes and the composition of the relevant gene families remain unclear in many plant species. Here, we identified and characterized 11 families of monolignol biosynthesis genes in Salix matsudana Koidz. Based on phylogenetic analysis of lignin biosynthesis genes from nine angiosperm species (Arabidopsis thaliana, Oryza sativa, Zea mays, Solanum lycopersicum, S. suchowensis, S. purpurea, Populus euphratica, P. trichocarpa, and S. matsudana), the 11 gene families could be divided into two classes that differed in their apparent evolutionary history. We compared the distribution of lignin biosynthesis genes between the two sub-genomes (At and Bt) of S. matsudana and found that more duplicated genes were present in the Bt sub-genome. We analyzed RNA sequencing data from two parents of contrasting height and two of their F1 progeny, and detected 23 differentially expressed genes (DEGs) that may regulate accelerated growth. We analyzed the promoter regions of the lignin-related DEGs and identified several hormone-related (auxin, ethylene, and cytokinin) transcription factor binding sites. These results provide an important foundation for future studies on the molecular mechanisms and genetic regulation of lignin biosynthesis and its relationship to accelerated growth in forest trees.

Functional mapping of gravitropism and phototropism for a desert tree, Populus euphratica.

Background: Plants have evolved the dual capacity for maximizing light assimilation through stem growth (phototropism) and maximizing water and nutrient absorption through root growth (gravitropism). Previous studies have revealed the physiological and molecular mechanisms of these two processes, but the genetic basis for how gravitropism and phototropism interact and coordinate with one another to determine plant growth remains poorly understood. Methods: We designed a seed germination experiment using a full-sib F1 family of Populus euphratica to simultaneously monitor the gravitropic growth of the radicle and the phototropic growth of the plumule throughout seedling ontogeny. We implemented three functional mapping models to identify quantitative trait loci (QTLs) that regulate gravitropic and phototropic growth. Univariate functional mapping dissected each growth trait separately, bivariate functional mapping mapped two growth traits simultaneously, and composite functional mapping mapped the sum of gravitropic and phototropic growth as a main axis. Results: Bivariate model detected 8 QTLs for gravitropism and phototropism (QWRF, GLUR, F-box, PCFS4, UBQ, TAF12, BHLH95, TMN8), composite model detected 7 QTLs for growth of main axis (ATL8, NEFH, PCFS4, UBQ, SOT16, MOR1, PCMP-H), of which, PCFS4 and UBQ were pleiotropically detected with the both model. Many of these QTLs are situated within the genomic regions of candidate genes. Conclusions: The results from our models provide new insight into the mechanisms of genetic control of gravitropism and phototropism in a desert tree, and will stimulate our understanding of the relationships between gravity and light signal transduction pathways and tree adaptation to arid soil.

Genetic diversity and construction of core conservation units of the natural populations of <i>Populus euphratica</i> in Northwest China

Genetic diversity and construction of core conservation units of the natural populations of <i>Populus euphratica</i> in Northwest China

Nitrogen and phosphorus uptake and biomass production in four riparian plants grown in subsurface flow constructed wetlands for urban wastewater treatment

Riparian woodlands play a multiple ecological and environmental role, including control of non-point source pollution and increasing of nutrients retention. Four riparian species (Arundo donax L., Salix purpurea L., Populus euphratica Olivier and Tamarix gallica L.) were tested comparatively in tertiary treatment and/or secondary one under a Mediterranean climate. Mesocosm inlets and outlets have been sampled every two weeks, during 21 successive months, and analyzed to determine nitrogen (N) and phosphorus (P) contents. Growth, biomass production and/or NP contents of macrophytes were monitored during three successive vegetation periods. Results show that A. donax presents a higher growth rate (2.39 cm d−1) during the vegetation period, and a large harvestable biomass (118–134 t dry weight.ha−1.y−1) and aboveground N/P accumulation (1.55–2.13 t N.ha−1.y−1/0.16–0.17 t P.ha−1.y−1). S. purpurea and T. gallica show medium performances in this respect. In addition, A. donax-Mesocosm retains more particulate and dissolved forms of total nitrogen and total phosphorus, and orthophosphates in both treatment levels. In tertiary treatment, the annual collecting of aboveground biomass contributes to the export of 31.4% N-14.1% P and 14.5% N-7.71% P removed, by A. donax and T. gallica mesocosms in the same order. Collecting biomass of riparian plant grown in subsurface flow constructed wetland promotes more N retention when compared to the P one.

Potential Carbon Absorption by Tree-Stand Phytomass in the Course of Tugai Forest Restoration

A predictive system has been developed to assess carbon absorption by tree-stand phytomass in the course of the tugai forest restoration in the Ili River valley (Republic of Kazakhstan). This system comprises constraint equations describing the relationships between the forest-stand density and age, average stand height and age, and average tree diameter and stand density; it also includes allometric constraint equations describing the relationships between the forest-stand phytomass and forest valuation parameters. The predictive system makes it possible to forecast the carbon absorption and sequestration by the phytomass with a time-step of 1 year. The system was used to model the development dynamics of desert poplar of three quality classes, oleaster, and white willow. At the end of the 30-year-long forest restoration project, the phytomass carbon will amount to 50.14 t C ha–1 for the desert poplar, quality class I; 40.51 t C ha–1 for the desert poplar, quality class II; 35.79 C ha–1 for the desert poplar, quality class III; 15.61 C ha–1 for the oleaster; and 92.52 t C ha–1 for the white willow. The age of the maximum carbon absorption capacity differs significantly for various forest stands: 9 years for the oleaster; 13 for the desert poplar, quality class I; 16 years for the desert poplar, quality class II, and white willow; and 23 years for the desert poplar, quality class III. The developed system can be used to forecast the potential carbon absorption for other forest-forming species subject to the identification of the equation parameters using the regression method or on the basis of assumptions of the initial and maximum stand density and average height values.

Measuring and modeling evapotranspiration of a Populus euphratica forest in northwestern China

Vegetation is sparsely distributed in the arid regions of northwestern China, and accurately measuring and partitioning of evapotranspiration is of importance for ecosystems in such areas. In this study, we measured and analyzed diurnal and phenological variations in evapotranspiration using the eddy–covariance method based on the Penman–Monteith, Priestley–Taylor, Shuttleworth–Wallace models, a newly proposed improved dual source model and a clumped model in a forest reserve in the Ejin oasis of Populus euphratica in 2015 and 2016 growing seasons. A sensitivity analysis was performed for the models with higher accuracies and we examined the biotic and abiotic controls on evapotranspiration. The results show that the total amounts of evapotranspiration during the two growing seasons in 2015 and 2016 were 622 and 612 mm, respectively. Phenological variations in evapotranspiration produced single-peak curves, while diurnal variations reflected the influence of high temperatures on some afternoons. The Priestley–Taylor and the improved dual source models gave the most accurate evapotranspiration values at the daily scale and appeared to be most suitable for the estimation of evapotranspiration for the species in arid regions. In addition, both models were the most sensitive to net radiation (Rn).

Leafing intensity decreases with increasing water table depth and plant height in Populus euphratica, a desert riparian species

Leafing intensity, which refers to the number of leaves per unit shoot size, is a key architectural trait that is closely linked to plant hydraulics. However, it remains unclear how leafing intensity is regulated by deeper water tables and greater plant heights (i.e., with both necessitating longer hydraulic paths to foliage). As there are diminishing photosynthetic returns from incrementally increased hydraulic support costs with longer hydraulic paths, we predict that leafing intensity would decrease accordingly. To test the prediction, we examined the hydraulic constraints on leafing intensity in a desert riparian species, Populus euphratica. We sampled 1863 shoots from 96 trees with varying heights at contrasting water table depths along the Tarim River corridor in Northwest China. Results showed that midday shoot water potentials decreased with water table depth and plant height. P. euphratica trees had fewer leaves for a given shoot length with deeper water tables, while the increase in leaf number per unit increment of shoot length was constant across water table levels. Although the increase in leaf number per unit increment of shoot length was slightly higher in tall P. euphratica trees, they had fewer leaves at the onset of shoot elongation, and at the grand mean of shoot length across height classes. Overall, the lower leafing intensity with increasing water table depth and plant height highlights the role of hydraulic path length in regulating leaf-shoot allometry. These results also suggest the functional significance of leafing intensity in equilibrating photosynthetic gains with water supplies under varying hydraulic constraints, especially for plants inhabiting drylands.

NaCl-altered oxygen flux profiles and H+-ATPase activity in roots of two contrasting poplar species.

Maintaining mitochondrial respiration is crucial for proving ATP for H+ pumps to continuously exclude Na+ under salt stress. NaCl-altered O2 uptake, mitochondrial respiration and the relevance to H+-ATPase activity were investigated in two contrasting poplar species, Populus euphratica (salt-tolerant) and Populus popularis 35-44 (salt-sensitive). Compared with P. popularis, P. euphratica roots exhibited a greater capacity to extrude Na+ under NaCl stress (150mM). The cytochemical analysis with Pb(NO3)2 staining revealed that P. euphratica root cells retained higher H+ hydrolysis activity than the salt-sensitive poplar during a long term (LT) of increasing salt stress (50-200mM NaCl, 4weeks). Long-sustained activation of proton pumps requires long-lasting supply of energy (adenosine triphosphate, ATP), which is delivered by aerobic respiration. Taking advantage of the vibrating-electrodes technology combined with the use of membrane-tipped, polarographic oxygen microelectrodes, the species, spatial and temporal differences in root O2 uptake were characterized under conditions of salt stress. Oxygen uptake upon NaCl shock (150mM) was less declined in P. euphratica than in P. popularis, although the salt-induced transient kinetics were distinct from the drastic drop of O2 caused by hyperosmotic shock (255mM mannitol). Short-term (ST) treatment (150mM NaCl, 24h) stimulated O2 influx in P. euphratica roots, and LT-treated P. euphratica displayed an increased O2 influx along the root axis, whereas O2 influx declined with increasing salinity in P. popularis roots. The spatial localization of O2 influxes revealed that the apical zone was more susceptible than the elongation region upon high NaCl (150, 200mM) during ST and LT stress. Pharmacological experiments showed that the Na+ extrusion and H+-ATPase activity in salinized roots were correspondingly suppressed when O2 uptake was inhibited by a mitochondrial respiration inhibitor, NaN3. Therefore, we conclude that the stable mitochondrial respiration energized H+-ATPase of P. euphratica root cells for maintaining Na+ homeostasis under salt environments.

Topsoil Carbon Stock and Soil Physicochemical Properties in Riparian Forests and Agricultural Lands of Southwestern Iran

This study aimed to evaluate subsoil carbon stock in different stands of riparian forests. Four different sites in the studied riparian forests located in Behbahan in southern Iran, pure Populus euphratica, Tamarix arceuthoides stands, and mixed T. arceuthoides-P. euphratica stands as well as agricultural lands were examined. One hundred and three soil samples were randomly taken at depths of 0–20 cm from all studied sites. Soil carbon content and the physiochemical properties pH, organic carbon, nitrogen, phosphorus, potassium, calcium carbonate, bulk density, and soil texture were determined in the laboratory. The results indicated that soil carbon stocks reach 52.9, 48.5, 25.9, and 25.8 t ha–1 in P. euphratica stands, agricultural lands, mixed T. arceuthoides-P. euphratica stands, and T. arceuthoides stands, respectively. There was no significant difference in soil carbon content between the P. euphratica stands and agricultural lands, but there was a significant difference between T. arceuthoides stands and mixed T. arceuthoides-P. euphratica stands. The high soil carbon content in agricultural lands was probably because of alfalfa and the use of organic fertilizer, like manure, because alfalfa was planted in most of the agricultural lands, and this plant species can store atmospheric nitrogen and, consequently, increase the carbon content in the soil. Furthermore, greater soil biological activity in the P. euphratica stands compared with the T. arceuthoides stands might be responsible for the higher soil carbon content in the P. euphratica stands. The physiochemical properties of soil also play important roles in soil carbon content, the most important of which are soil organic carbon, bulk density, and clay, respectively.

Populus euphratica annexin1 facilitates cadmium enrichment in transgenic Arabidopsis

Phytoremediation offers a great potential for affordable remediation of heavy metal (HM)−polluted soil and water. Screening and identifying candidate genes related to HM uptake and transport is prerequisite for improvement of phytoremediation by genetic engineering. Using the cadmium (Cd)−hypersensitive Populus euphratica, an annexin encoding gene facilitating Cd enrichment was identified in this study. With a 12 h exposure to CdCl2 (50–100 μM), P. euphratica cells down-regulated transcripts of annexin1 (PeANN1). PeANN1 was homologue to Arabidopsis annexin1 (AtANN1) and localized mainly to the plasma membrane (PM) and cytosol. Compared with wild type and Atann1 mutant, PeANN1 overexpression in Arabidopsis resulted in a more pronounced decline in survival rate and root length after a long-term Cd stress (10 d, 50 μM), due to a higher cadmium accumulation in roots. PeANN1−transgenic roots exhibited enhanced influx conductance of Cd2+ under cadmium shock (30 min, 50 μM) and short-term stress (12 h, 50 μM). Noteworthy, the PeANN1-facilitated Cd2+ influx was significantly inhibited by a calcium-permeable channel (CaPC) inhibitor (GdCl3) but was promoted by 1 mM H2O2, indicating that Cd2+ entered root cells via radical-activated CaPCs in the PM. Therefore, PeANN1 can serve as a candidate gene for improvement of phytoremediation by genetic engineering.

DESIGN AND PROPERTIES OF COMPOSITE SUSTAINABLE BUILDING MATERIAL BY USING WASTE HDPE

The aim of this study is to produce next generation of sustainable building materials by using wood veneers and waste plastics. In this study, plywood was produced using poplar (Populus Euphratica) veneer and waste high-density polyethylene (HDPE). Four different high-density polyethylene amounts were used (170 g/m², 200 g/m², 240 g/m² and 280 g/m²). Some technological properties such as density, modulus of elasticity (MOE), modulus of rupture (MOR), and impact bending (IB) were investigated according to Turkish standards TS EN 323, TS EN 310, TS EN 310 and TS 2477, respectively. According to obtained data, the density, MOR, MOE and IB values are increased by increasing the usage rate of HDPE in composite production.