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Two strangers
\"An intelligent, slum-dwelling teenage girl takes drastic measures to survive when her father throws her out of her home, in this spellbinding historical saga. Poplar, London, 1920. Fourteen-year-old Victoria Keats is horrified when her father demands that she go to work for wealthy Mr Preston - everyone knows why he takes young girls into his house. But her violent father, who's never let her forget she's not the son he wanted, won't listen to her concerns - and when she stands up for herself, he throws her out of their dingy little house in the slums. Intelligent, book-loving Vicki vows to make her father regret this day; but she is all alone in the world. Despite her courage and quick wits, it seems likely she will starve - until two men, both complete strangers, provide her with no-strings-attached help. As Vicki's life improves beyond all recognition, she can't help but fixate on the mystery of these two good Samaritans: who were they? And why did they help her? She determines to find the men and thank them, but tracking them down may be harder - and more life-changing - than she thinks...\"--Provided by publisher.
Book
Cottonwood and the River of Time
Cottonwood and the River of Time looks at some of the approaches scientists have used to unravel the puzzles of the natural world. With a lifetime of work in forestry and genetics to guide him, Reinhard Stettler celebrates both what has been learned and what still remains a mystery as he examines not only cottonwoods but also trees more generally, their evolution, and their relationship to society.
Cottonwoods flourish on the verge, near streams and rivers. Their life cycle is closely attuned to the river's natural dynamics. An ever-changing floodplain keeps generating new opportunities for these pioneers to settle and prepare the ground for new species. Perpetual change is the story of cottonwoods -- but in a broader sense, the story of all trees and all kinds of life. Through the long parade of generation after generation, as rivers meander and glaciers advance and retreat, trees have adapted and persisted, some for thousands of years. How do they do this? And more urgently, what lessons can we learn from the study of trees to preserve and manage our forests for an uncertain future?
In his search for answers, Stettler moves from the floodplain of a West Cascade river, where seedlings compete for a foothold, to mountain slopes, where aspens reveal their genetic differences in colorful displays; from the workshops of Renaissance artists who painted their masterpieces on poplar to labs where geneticists have recently succeeded in sequencing a cottonwood's genome; from the intensively cultivated tree plantations along the Columbia to old-growth forests challenged by global warming.
Natural selection and adaptation, the comparable advantages and disadvantages of sexual versus asexual reproduction, the history of plant domestication, and the purposes, risks, and potential benefits of genetic engineering are a few of the many chapters in this story. By offering lessons in how nature works, as well as how science can help us understand it, Cottonwood and the River of Time illuminates connections between the physical, biological, and social worlds.
eBook
A Method for Extracting the Tree Feature Parameters of IPopulus tomentosa/I in the Leafy Stage
With the advancement of 3D information collection technology, such as LiDAR scanning, information regarding the trees growing on large, complex landscapes can be obtained increasingly more efficiently. Such forestry data can play a key role in the cultivation, monitoring, and utilization of artificially planted forests. Studying the tree growth of artificially planted trees during the leafy period is an important part of forestry and ecology research; the extraction of tree feature parameters from the point clouds of leafy trees, obtained via terrestrial laser scanning (TLS), is an important area of research. The separation of foliage and stem point clouds is an important step in extracting tree feature parameters from data collected via TLS. By modeling the separated stem point clouds, we can obtain parameters such as a tree’s diameter at breast height (DBH), the number of branches, and the relationship between these and other parameters. However, there are always problems with the collected foliated tree point clouds; it is difficult to separate the point clouds into foliage and stems, yielding poor separation results. To address this challenge, the current study uses a deep learning-based method to train a mixture of non-foliated and foliated point clouds from artificially planted trees to semantically segment the foliage labels from the stem labels of these trees. And this study focused on a Chinese white poplar (Populus tomentosa Carr.) plantation stand. At the same time, the method of this study greatly reduces the workload of labeling foliated point clouds and training models; an overall segmentation accuracy of 0.839 was achieved for the foliated Populus tomentosa point clouds. By building the Quantitative Susceptibility Mapping (QSM) model of the segmented point clouds, a mean value of 0.125 m for the tree diameter at breast height, and a mean value of 14.498 m for the height of the trees was obtained for the test set. The residual sum of squares for the diameter at breast height was 0.003 m, which was achieved by comparing the calculated value with the measured value. This study employed a semantic segmentation method that is applicable to the foliated point clouds of Populus tomentosa trees, which solves the difficulties of labeling and training models for the point clouds and improves the segmentation precision of stem-based point clouds. It offers an efficient and reliable way to obtain the characteristic parameters and stem analyses of Populus tomentosa trees.
Journal Article
Elucidating the Genetic Basis of Columnar Upright Architecture in Populus Through CRISPR Disruption of TILLER ANGLE CONTROL1
Narrow or upright branch angles in shoots and leaves lead to columnar, upright‐growing tree architectures, as observed in various tree species such as Lombardy poplar ( Populus nigra var. italica ). However, the genetic mechanism underlying this unique growth habit in Lombardy poplar has not yet been elucidated. In this study, we identified a nonsense mutation in the PnTAC1‐1 gene of Lombardy poplar, an ortholog of the rice TILLER ANGLE CONTROL 1 ( TAC1 ) gene known to regulate branch angles. To confirm the functional role of TAC1 in regulating tree architecture, we generated transgenic hybrid poplar ( Populus alba × Populus glandulosa , clone BH) with targeted mutations in TAC1 homologues using CRISPR/Cas9 gene editing. The resulting TAC1‐CRISPR hybrid poplars exhibited a stable upright branching phenotype closely resembling that of Lombardy poplar, as confirmed by two consecutive years of living modified organism (LMO) field trials. Anatomical analysis revealed increased cell elongation specifically in the lower petiole region and significantly enhanced gravitropic responses in TAC1‐CRISPR hybrid poplars compared to wild‐type BH clones. RNA sequencing analysis further demonstrated that TAC1 disruption triggered extensive transcriptomic reprogramming of axillary meristem, notably altering hormonal and photomorphogenic signalling pathways, which redirected auxin accumulation toward the abaxial region and increased gibberellin biosynthesis, ultimately promoting upright growth. This research uncovers the genetic and molecular mechanisms behind columnar growth in poplar and provides a promising approach for engineering tree architecture to enhance planting density, harvest efficiency and woody biomass productivity.
Journal Article
Conversion of carlactone to carlactonoic acid is a conserved function of MAX1 homologs in strigolactone biosynthesis
Strigolactones (SLs) are a class of plant hormones which regulate shoot branching and function as host recognition signals for symbionts and parasites in the rhizosphere. However, steps in SL biosynthesis after carlactone (CL) formation remain elusive. This study elucidated the common and diverse functions of MAX1 homologs which catalyze CL oxidation.
We have reported previously that Arabidopsis MAX1 converts CL to carlactonoic acid (CLA), whereas a rice MAX1 homolog has been shown to catalyze the conversion of CL to 4-deoxyorobanchol (4DO). To determine which reaction is conserved in the plant kingdom, we investigated the enzymatic function of MAX1 homologs in Arabidopsis, rice, maize, tomato, poplar and Selaginella moellendorffii.
The conversion of CL to CLA was found to be a common reaction catalyzed by MAX1 homologs, and MAX1s can be classified into three types: A1-type, converting CL to CLA; A2-type, converting CL to 4DO via CLA; and A3-type, converting CL to CLA and 4DO to orobanchol.
CLA was detected in root exudates from poplar and Selaginella, but not ubiquitously in other plants examined in this study, suggesting its role as a species-specific signal in the rhizosphere. This study provides new insights into the roles of MAX1 in endogenous and rhizosphere signaling.
Journal Article
Genome-wide analysis and expression profile of the bZIP gene family in poplar
Background
The bZIP gene family, which is widely present in plants, participates in varied biological processes including growth and development and stress responses. How do the genes regulate such biological processes? Systems biology is powerful for mechanistic understanding of gene functions. However, such studies have not yet been reported in poplar.
Results
In this study, we identified 86 poplar bZIP transcription factors and described their conserved domains. According to the results of phylogenetic tree, we divided these members into 12 groups with specific gene structures and motif compositions. The corresponding genes that harbor a large number of segmental duplication events are unevenly distributed on the 17 poplar chromosomes. In addition, we further examined collinearity between these genes and the related genes from six other species. Evidence from transcriptomic data indicated that the bZIP genes in poplar displayed different expression patterns in roots, stems, and leaves. Furthermore, we identified 45 bZIP genes that respond to salt stress in the three tissues. We performed co-expression analysis on the representative genes, followed by gene set enrichment analysis. The results demonstrated that tissue differentially expressed genes, especially the co-expressing genes, are mainly involved in secondary metabolic and secondary metabolite biosynthetic processes. However, salt stress responsive genes and their co-expressing genes mainly participate in the regulation of metal ion transport, and methionine biosynthetic.
Conclusions
Using comparative genomics and systems biology approaches, we, for the first time, systematically explore the structures and functions of the bZIP gene family in poplar. It appears that the bZIP gene family plays significant roles in regulation of poplar development and growth and salt stress responses through differential gene networks or biological processes. These findings provide the foundation for genetic breeding by engineering target regulators and corresponding gene networks into poplar lines.
Journal Article
Biomass Allocation and Root Characteristics of Early-Stage Poplars (Populus spp.) for Assessing Their Water-Deficit Response During SRC Establishment
Early above- and belowground biomass fractionation, root diameter composition and allocation of cumulated fine root length per total leaf area of Populus clones have been measured for a pre-assessment of the risk for plantation establishment during spring drought conditions. Four clones of Populus × euramericana, and one P. nigra × P. maximowiczii clone (cv. Max 3), were planted in sandy mix substrate and were exposed to one normal and one deficit watering regime over 65-day greenhouse experiments conducted during early summer. The P. × euramericana hybrids showed plasticity of their root biomass fractions. Although clone Max 3 was among the productive clones, even under deficit watering, it was not able to respond plastically to deficit watering. It showed no increase in the root biomass fraction and no increase in the ratio of cumulated fine root length per total leaf area. Therefore, the clone Max 3 should not be planted under high risk for spring drought. Planting the investigated P. × euramericana clones under water deficit likely involves a lower risk, but clone differences within this group must be considered. It can be concluded that the water deficit response of biomass allocation to roots and of the ratio of fine root length per unit leaf area is suitable traits to improve drought risk assessments that are based on yield response of poplar clones to drought. Percent plant loss data and the yield at the end of the first SRC rotation will be suitable to verify the present greenhouse assessment.
Journal Article
Extracts of Poplar Buds (Populus balsamifera L., Populus nigra L.) and Lithuanian Propolis: Comparison of Their Composition and Biological Activities
Balsam poplar and black poplar (Populus balsamifera L. and Populus nigra L.) buds that grow in Lithuania are the primary source of propolis, therefore it is proper to evaluate and compare the composition of these raw plant materials and propolis quantitatively and qualitatively. Propolis and balsamic poplar bud extract are dominated by p-coumaric acid and black poplar-caffeic acid. Antioxidant activity was evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), FRAP (ferric-reducing antioxidant power) and CUPRAC (cupric reducing antioxidant capacity) methods and all extracts showed antioxidant activity, and obtained results correlated with the obtained amounts of phenolic compounds and flavonoids in the extracts. Studies of antimicrobial activity have shown that all extracts have a growth inhibitory effect against Staphylococcus aureus and Candida albicans, but the extract of balsam poplar buds showed the most significant effect of such kind. Considering the results of the research, it can be stated that balsam poplar buds cultured in Lithuania are the primary raw material of propolis, which is rich in phenolic compounds with antioxidant properties and is a promising raw material for pharmaceutical purposes.
Journal Article