Estimation of the transpiration rate for a tree is generally based on sap flow measurements within the hydro-active stem xylem. In this study, radial variation of sap flow velocity（Js） was investigated at five depth...Estimation of the transpiration rate for a tree is generally based on sap flow measurements within the hydro-active stem xylem. In this study, radial variation of sap flow velocity（Js） was investigated at five depths of the xylem（1, 2, 3, 5 and 8 cm under the cambium） in three mature Xinjiang poplar（Populus alba L. var. pyramidalis） trees grown at the Gansu Minqin National Studies Station for Desert Steppe Ecosystem from May to October 2011. Thermal dissipation probes of various lengths manufactured according to the Granier＇s design were installed into each tree for simultaneous observation of the radial patterns of Js through the xylem. The radial patterns were found to fit the four-parameter GaussAmp equation. The peak Js was about 27.02±0.95 kg/（dm2？d） at approximately 3 to 5 cm deep from the cambium of the three trees,and the lowest Js appeared at 1 cm deep in most of the time. Approximately 50% of the total sap flow in Xinjiang poplar occurred within one-third of the xylem from its outer radius, whereas 90% of the total sap flow occurred within two-fifth of the xylem. In addition, the innermost point of the xylem（at 8-cm depth）, which appeared as the penultimate sap flow in most cases during the study period, was hydro-active with Js,8 of 7.55±3.83 kg/（dm2？d）. The radial pattern of Js was found to be steeper in midday than in other time of the day, and steeper diurnal fluctuations were recorded in June, July and August（the mid-growing season）. Maximum differences between the lowest Js（Js,1 or Js,8） and the highest Js（Js,3 or Js,5） from May through October were 12.41, 17.35, 16.30, 18.52, 12.60 and 16.04 g/（cm2？h）, respectively. The time-dependent changes of Js along the radial profile（except at 1-cm depth） were strongly related to the reference evapotranspiration（ET0）. Due to significant radial variability of Js, the mean daily sap flow at the whole-tree level could be over-estimated by up to 29.69% when only a single probe at depth of 2 cm was used. However, the accuracy of the estimation of sap flow in Xinjiang poplar could be significantly improved using a correction coefficient of 0.885.展开更多
Populus alba × P.glandulosa clone 84 K,derived from South Korea,is widely cultivated in China and used as a model in the molecular research of woody plants because of hi gh gene transformation efficiency.Here,we ...Populus alba × P.glandulosa clone 84 K,derived from South Korea,is widely cultivated in China and used as a model in the molecular research of woody plants because of hi gh gene transformation efficiency.Here,we combined63-fold coverage Illumina short reads and 126-fold coverage PacBio long reads to assemble the genome.Due to the hi gh heterozygosity level at 2.1% estimated by k-mer analysis,we exploited TrioCanu for genome assembly.The PacBio clean subreads of P.alba × P.glandulosa were separated into two parts according to the similarities,compared with the parental genomes of P.alba and P.glandulosa.The two parts of the subreads were assembled to two sets of subgenomes comprising subgenome A(405.31 Mb,from P.alba)and subgenome G(376.05 Mb,from P.glandulosa) with the contig N50 size of 5.43 Mb and 2.15 Mb,respectively.A high-quality P.alba × P.glandulosa genome assembly was obtained.The genome size was 781.36 Mb with the contig N50 size of 3.66 Mb and the longest contig was 19.47 Mb.In addition,a total of 176.95 Mb(43.7%),152.37 Mb(40.5%)of repetitive elements were identified and a total of 38,701 and 38,449 protein-coding genes were predicted in subgenomes A and G,respectively.For functional annotation,96.98% of subgenome A and 96.96% of subgenome G genes were annotated with public databases.This de novo assembled genome will facilitate systematic and comprehensive study,such as multi-omics analysis,in the model tree P.alba X P.glandulosa.展开更多
Static tests under cyclic loading were carried out on Populus alba var. pyramidalis to determine its characteristic curves of restoring forces. The results show that P alba var. pyramidalis had good elastic performanc...Static tests under cyclic loading were carried out on Populus alba var. pyramidalis to determine its characteristic curves of restoring forces. The results show that P alba var. pyramidalis had good elastic performance. There was degradation of strength and stiffness under cyclic loading and unloading, where characteristic curves of restoring forces ofP. alba var. pyrarnidalis assumed a ＂flat and contrary S-shape＂ form. Simultaneously, P alba vat. pyramidalis showed typical characteristics of brittle destruction under large high peak loading and unloading. Furthermore, dynamic tests were carried out under wind loads to obtain dynamic displacement curves and dynamic strain curves. P alba var. pyramidalis reflected its stochastic dynamic performance in building up its resistance to the stochastic wind loads and its dynamically hysteretic properties. The dynamic response of this species was random and fuzzy under stochastic wind loads. This study has theoretical significance and reference value to research on the static characteristics and wind-induced dynamic performance of forests.展开更多
Because overexpression of Vitreoscilla hemoglobin gene(Vgb)gene in plants can enhance tolerance to waterlogging,here Vgb was inserted into Populus alba×glandulosa to investigate its expression and effects on grow...Because overexpression of Vitreoscilla hemoglobin gene(Vgb)gene in plants can enhance tolerance to waterlogging,here Vgb was inserted into Populus alba×glandulosa to investigate its expression and effects on growth and physiological responses to waterlogging stress in the transgenic poplars.Southern blotting and RT-PCR analysis of Vgb-transgenic P.alba×glandulosa showed that the Vgb gene was integrated into the genome of the V13-81 and V13-85 transgenic lines and expressed.In greenhouse waterlogging stress tests,mortality of the transgenic poplar was significant lower than that of nontransgenic plants with increasing treatment time from 2 to 22 days.The transgenic plants had higher chlorophyll content and less chloroplast damage than in the control plants.Additionally,starch accumulation increased,and growth was enhanced in the transgenic plants,suggesting that the Vgb-expressing lines had improved energy reserves.Field trials of the transgenic poplar suggested that Vgb expression promotes growth and influences wood quality.Taken together,our results suggest that the expression of Vgb can increase the accumulation of chlorophyll and starch in the transgenic poplar,improve its ability to endure flooding,and improve growth and wood quality of the transgenic plants.展开更多
Laboratory feeding experiments with the poplar aphid, Chaitophorus populeti （Panzer）, feeding on transgenic poplar （P. alba × P. glandulosa） varieties C13-5 and C013-5, were carried out to study the effect of...Laboratory feeding experiments with the poplar aphid, Chaitophorus populeti （Panzer）, feeding on transgenic poplar （P. alba × P. glandulosa） varieties C13-5 and C013-5, were carried out to study the effect of transgenic poplar on the ladybird Harmonia axyridis （Pallas）. The mortality and development time of the immature stages, the eclosion rate and body mass of H. axyridis were measured. The results indicated that C. populeti feeding on different varieties of transgenic plants had no statistically significant ef- fect on the mortality ofH. axyridis larvae. The development time of larval and pupal stages were not significantly different between the two transgenic poplars and a non-transgenic poplar. Furthermore, the body mass and eclosion rate did not show any difference between the H. axyridis feeding on aphids reared on transgenic plants and those from non-transgenic plants. It is suggested that transgenic plants have no deleterious effect on the predatory ladybird.展开更多
High-throughputsingle-cellRNAsequencing(sc RNA-seq) has advantages over traditional RNA-seq to explore spatiotemporal information on gene dynamic expressions in heterogenous tissues. We performed Drop-seq, a method fo...High-throughputsingle-cellRNAsequencing(sc RNA-seq) has advantages over traditional RNA-seq to explore spatiotemporal information on gene dynamic expressions in heterogenous tissues. We performed Drop-seq, a method for the dropwise sequestration of single cells for sequencing, on protoplasts from the differentiating xylem of Populus alba × Populus glandulosa. The sc RNA-seq profiled9,798 cells, which were grouped into 12 clusters.Through characterization of differentially expressed genes in each cluster and RNA in situ hybridizations,we identified vessel cells, fiber cells, ray parenchyma cells and xylem precursor cells. Diffusion pseudotime analyses revealed the differentiating trajectory of vessels, fiber cells and ray parenchyma cells and indicated a different differentiation process between vessels and fiber cells, and a similar differentiation process between fiber cells and ray parenchyma cells. We identified marker genes for each cell type(cluster) and key candidate regulators during developmental stages of xylem cell differentiation. Our study generates a high-resolution expression atlas of wood formation at the single cell level and provides valuable information on wood formation.展开更多
In this study,genetic stability of foreign genes was checked by using PCR technology. A total of 4 lines of soil samples from transgenic and non-transgenic control Populus alba×P.glandulosa and the soil samples f...In this study,genetic stability of foreign genes was checked by using PCR technology. A total of 4 lines of soil samples from transgenic and non-transgenic control Populus alba×P.glandulosa and the soil samples from the stands were collected in two successive years,and the bacteria,fungi and antinomyces were isolated by using flat dilution method to determine their quantities. The results demonstrated that target genes were stable present in the genome of transgenic poplar. We found that three kinds of soil microorganism appeared different trends within different months and different years. The ANOVA and multiple comparison analyses revealed that there was no significant difference in quantity of the soil microorganisms among most poplar lines at the same time point. Meanwhile,significant differences of the soil microorganism community were found among several transgenic lines,and between a few transgenic and non-transgenic lines,but they did not show any relation to the type and number of foreign genes. Our preliminary results indicated that the 2-year-old transgenic poplar growing in field had no significant effects on soil microorganisms.展开更多
基金supported by the National Natural Science Foundation of China (31070628)Field support for this research was provided by Gansu Minqin National Studies Station for Desert Steppe Ecosystem
文摘Estimation of the transpiration rate for a tree is generally based on sap flow measurements within the hydro-active stem xylem. In this study, radial variation of sap flow velocity（Js） was investigated at five depths of the xylem（1, 2, 3, 5 and 8 cm under the cambium） in three mature Xinjiang poplar（Populus alba L. var. pyramidalis） trees grown at the Gansu Minqin National Studies Station for Desert Steppe Ecosystem from May to October 2011. Thermal dissipation probes of various lengths manufactured according to the Granier＇s design were installed into each tree for simultaneous observation of the radial patterns of Js through the xylem. The radial patterns were found to fit the four-parameter GaussAmp equation. The peak Js was about 27.02±0.95 kg/（dm2？d） at approximately 3 to 5 cm deep from the cambium of the three trees,and the lowest Js appeared at 1 cm deep in most of the time. Approximately 50% of the total sap flow in Xinjiang poplar occurred within one-third of the xylem from its outer radius, whereas 90% of the total sap flow occurred within two-fifth of the xylem. In addition, the innermost point of the xylem（at 8-cm depth）, which appeared as the penultimate sap flow in most cases during the study period, was hydro-active with Js,8 of 7.55±3.83 kg/（dm2？d）. The radial pattern of Js was found to be steeper in midday than in other time of the day, and steeper diurnal fluctuations were recorded in June, July and August（the mid-growing season）. Maximum differences between the lowest Js（Js,1 or Js,8） and the highest Js（Js,3 or Js,5） from May through October were 12.41, 17.35, 16.30, 18.52, 12.60 and 16.04 g/（cm2？h）, respectively. The time-dependent changes of Js along the radial profile（except at 1-cm depth） were strongly related to the reference evapotranspiration（ET0）. Due to significant radial variability of Js, the mean daily sap flow at the whole-tree level could be over-estimated by up to 29.69% when only a single probe at depth of 2 cm was used. However, the accuracy of the estimation of sap flow in Xinjiang poplar could be significantly improved using a correction coefficient of 0.885.
基金supported by grants CAFYBB2017ZY001 and TGB2016001 from Fundamental Research Funds of the Chinese Academy of Forestry。
文摘Populus alba × P.glandulosa clone 84 K,derived from South Korea,is widely cultivated in China and used as a model in the molecular research of woody plants because of hi gh gene transformation efficiency.Here,we combined63-fold coverage Illumina short reads and 126-fold coverage PacBio long reads to assemble the genome.Due to the hi gh heterozygosity level at 2.1% estimated by k-mer analysis,we exploited TrioCanu for genome assembly.The PacBio clean subreads of P.alba × P.glandulosa were separated into two parts according to the similarities,compared with the parental genomes of P.alba and P.glandulosa.The two parts of the subreads were assembled to two sets of subgenomes comprising subgenome A(405.31 Mb,from P.alba)and subgenome G(376.05 Mb,from P.glandulosa) with the contig N50 size of 5.43 Mb and 2.15 Mb,respectively.A high-quality P.alba × P.glandulosa genome assembly was obtained.The genome size was 781.36 Mb with the contig N50 size of 3.66 Mb and the longest contig was 19.47 Mb.In addition,a total of 176.95 Mb(43.7%),152.37 Mb(40.5%)of repetitive elements were identified and a total of 38,701 and 38,449 protein-coding genes were predicted in subgenomes A and G,respectively.For functional annotation,96.98% of subgenome A and 96.96% of subgenome G genes were annotated with public databases.This de novo assembled genome will facilitate systematic and comprehensive study,such as multi-omics analysis,in the model tree P.alba X P.glandulosa.
基金supported by the National Natural Science Foundation of China (Grant No. 30872071)
文摘Static tests under cyclic loading were carried out on Populus alba var. pyramidalis to determine its characteristic curves of restoring forces. The results show that P alba var. pyramidalis had good elastic performance. There was degradation of strength and stiffness under cyclic loading and unloading, where characteristic curves of restoring forces ofP. alba var. pyrarnidalis assumed a ＂flat and contrary S-shape＂ form. Simultaneously, P alba vat. pyramidalis showed typical characteristics of brittle destruction under large high peak loading and unloading. Furthermore, dynamic tests were carried out under wind loads to obtain dynamic displacement curves and dynamic strain curves. P alba var. pyramidalis reflected its stochastic dynamic performance in building up its resistance to the stochastic wind loads and its dynamically hysteretic properties. The dynamic response of this species was random and fuzzy under stochastic wind loads. This study has theoretical significance and reference value to research on the static characteristics and wind-induced dynamic performance of forests.
基金supported by the Basic Research Fund of RIF(Grant No.CAFYBB2017ZA001-3)the National Natural Science Foundation of China(Grant No.31700589)the Forestry Genetic Breeding National Key Laboratory(Chinese Academy of Forestry Sciences)Open Project(Grant No.TGB 2013005).
文摘Because overexpression of Vitreoscilla hemoglobin gene(Vgb)gene in plants can enhance tolerance to waterlogging,here Vgb was inserted into Populus alba×glandulosa to investigate its expression and effects on growth and physiological responses to waterlogging stress in the transgenic poplars.Southern blotting and RT-PCR analysis of Vgb-transgenic P.alba×glandulosa showed that the Vgb gene was integrated into the genome of the V13-81 and V13-85 transgenic lines and expressed.In greenhouse waterlogging stress tests,mortality of the transgenic poplar was significant lower than that of nontransgenic plants with increasing treatment time from 2 to 22 days.The transgenic plants had higher chlorophyll content and less chloroplast damage than in the control plants.Additionally,starch accumulation increased,and growth was enhanced in the transgenic plants,suggesting that the Vgb-expressing lines had improved energy reserves.Field trials of the transgenic poplar suggested that Vgb expression promotes growth and influences wood quality.Taken together,our results suggest that the expression of Vgb can increase the accumulation of chlorophyll and starch in the transgenic poplar,improve its ability to endure flooding,and improve growth and wood quality of the transgenic plants.
基金supported by the National Premier Special Funds for Study and Industrialization of Transgenic Plants (J2002-B-004)the National Natural Science and Technology Support Plan of China "the technology researchdemonstration of forestry-paper integrate project" (Grant No. 2006BAD32B)
文摘Laboratory feeding experiments with the poplar aphid, Chaitophorus populeti （Panzer）, feeding on transgenic poplar （P. alba × P. glandulosa） varieties C13-5 and C013-5, were carried out to study the effect of transgenic poplar on the ladybird Harmonia axyridis （Pallas）. The mortality and development time of the immature stages, the eclosion rate and body mass of H. axyridis were measured. The results indicated that C. populeti feeding on different varieties of transgenic plants had no statistically significant ef- fect on the mortality ofH. axyridis larvae. The development time of larval and pupal stages were not significantly different between the two transgenic poplars and a non-transgenic poplar. Furthermore, the body mass and eclosion rate did not show any difference between the H. axyridis feeding on aphids reared on transgenic plants and those from non-transgenic plants. It is suggested that transgenic plants have no deleterious effect on the predatory ladybird.
基金This work was supported by grants from Fundamental Research Funds of Chinese Academy of Forestry(CAFYBB2018ZY001-5 and CAFYBB2017ZY001)the National Natural Science Foundation of China(31670667)。
文摘High-throughputsingle-cellRNAsequencing(sc RNA-seq) has advantages over traditional RNA-seq to explore spatiotemporal information on gene dynamic expressions in heterogenous tissues. We performed Drop-seq, a method for the dropwise sequestration of single cells for sequencing, on protoplasts from the differentiating xylem of Populus alba × Populus glandulosa. The sc RNA-seq profiled9,798 cells, which were grouped into 12 clusters.Through characterization of differentially expressed genes in each cluster and RNA in situ hybridizations,we identified vessel cells, fiber cells, ray parenchyma cells and xylem precursor cells. Diffusion pseudotime analyses revealed the differentiating trajectory of vessels, fiber cells and ray parenchyma cells and indicated a different differentiation process between vessels and fiber cells, and a similar differentiation process between fiber cells and ray parenchyma cells. We identified marker genes for each cell type(cluster) and key candidate regulators during developmental stages of xylem cell differentiation. Our study generates a high-resolution expression atlas of wood formation at the single cell level and provides valuable information on wood formation.
文摘In this study,genetic stability of foreign genes was checked by using PCR technology. A total of 4 lines of soil samples from transgenic and non-transgenic control Populus alba×P.glandulosa and the soil samples from the stands were collected in two successive years,and the bacteria,fungi and antinomyces were isolated by using flat dilution method to determine their quantities. The results demonstrated that target genes were stable present in the genome of transgenic poplar. We found that three kinds of soil microorganism appeared different trends within different months and different years. The ANOVA and multiple comparison analyses revealed that there was no significant difference in quantity of the soil microorganisms among most poplar lines at the same time point. Meanwhile,significant differences of the soil microorganism community were found among several transgenic lines,and between a few transgenic and non-transgenic lines,but they did not show any relation to the type and number of foreign genes. Our preliminary results indicated that the 2-year-old transgenic poplar growing in field had no significant effects on soil microorganisms.
