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    20 March 2023, Volume 43 Issue 2
    An Overview and Prospect on Taxonomy of the Genus Populus
    Xueqin WAN, Yujie SHI, Jinliang HUANG, Jiaxuan MI, Yu ZHONG, Fan ZHANG, Lianghua CHEN
    2023, 43(2):  161-168.  doi:10.7525/j.issn.1673-5102.2023.02.001
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    Since Linnaeus established the genus Populus, many taxonomic studies have been carried out about it and some taxonomic systems have been proposed, while the taxonomy of Populus is still in the stage of traditional morphological classification around the world. Although the taxonomic hierarchy of ‘genus-section-species’ is adopted in many countries, in which has Populus plant distributed, there are great differences in the classification of species, subspecies and varieties. The taxonomists of China and the United States are the representatives of splitter and lumper respectively, and there is a huge gap in poplar classification between them, but each has advantages and disadvantages. Even in China, there are still many problems to be solved. The existing phylogenetic studies about the genus Populus provide useful information to taxonomic revision, but the actual contribution is small yet. The ultimate aim on poplar classification is to establish a unified taxonomic system based on phylogeny in the world. It requires a comprehensive classification based on both population and the concepts of integrated species, which integrates morphology, ecology, biogeography, genomic bioinformatics and evolutionary biology.

    Systematic and Evolutionary
    Study on Endangered Degree and Priority Conservation Sequence of Orchids in the Lower Reaches of Yarlung Zangbo River
    Xinxin YANG, Wenqian GU, Shujun ZHANG, Meng XING, Xingle QU, Jian LUO
    2023, 43(2):  169-178.  doi:10.7525/j.issn.1673-5102.2023.02.002
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    Based on the survey of orchid resources in the lower Yarlung Zangbo River region, the priority protection value of each endangered plant was quantitatively calculated using multiple evaluation indexes to determine the endangerment level and priority protection sequence of rare and endangered orchids in the region by combining data collection and specimen review. The endangerment level of 156 species of endangered orchids in 60 genera in the lower Yarlung Zangbo River region was evaluated, among which 15 species were in critically endangered(CR) status, 46 species in endangered(EN) status, 78 species in vulnerable(VU) status and 17 species in near threatened(NT) status; the priority protection range value was 0.853 9-0.416 8, among which 45 species were classified as Class Ⅰ protected plants, 72 species as Class Ⅱ protected plants, and 39 species as Class Ⅲ protected plants.The results of this study differ greatly from the endangered degree and priority protection level of various protected plant lists, and most of the orchids are under enhanced threat in this region, which is consistent with the real survival status of these orchids in the lower Yarlung Zangbo River area, and the protection of orchids in this region is urgent and should be given sufficient attention.

    Genetic and Breeding
    Effects of Abiotic Stresses on the Intracellular and Extracellular ATP Levels of Tobacco Suspension Cells
    Li LI, Xin WANG, Yuejing ZHANG, Lingyun JIA, Hailong PANG, Hanqing FENG
    2023, 43(2):  179-185.  doi:10.7525/j.issn.1673-5102.2023.02.003
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    In this study, the effects of NaCl, PEG(6000) and low temperature stresses on the levels of iATP (intracellular ATP) and eATP(extracellular ATP) of tobacco suspension cells BY-2(Nicotiana tabacum ‘Bright Yellow-2’) were studied respectively. The results showed that the tobacco suspension cells treated with 50-200 mmol·L-1 NaCl significantly increased membrane permeability(P<0.05), the levels of iATP and eATP decreased significantly at 100 and 200 mmol·L-1 NaCl stresses(P<0.05). With the increase of PEG mass concentration(50, 100 and 200 g·L-1), the membrane permeability and eATP level increased. Under 200 g·L-1 PEG stress, eATP level increased significantly to 3.4-fold of the control(P<0.05), iATP level decreased significantly to 0.5-fold of the control(P<0.05). After the treatment with low temperature at 0-10 ℃, the membrane permeability and iATP level increased to different extents. iATP level increased to 1.9-fold of the control at 0 ℃, while eATP level decreased significantly to 0.8-fold the control at 10 ℃(P<0.05). The above results indicate that iATP is the source of eATP in plant cells, iATP level is not the only factor that affects eATP level under abiotic stresses. The way in which plant cells transport ATP and other factors may affect eATP level under abiotic stresses.

    Genomic Survey Analysis of Endangered Plant Tetraena mongolica
    Ziyin WANG, Bingru LIU, Zihao LI, Jifei WANG, Pengbin YANG
    2023, 43(2):  186-193.  doi:10.7525/j.issn.1673-5102.2023.02.004
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    To assess the size and complexity of the genome of the endangered plant Tetraenamongolica, and reveal the hyper-arid mechanism of T.mongolica and further explore its characteristic genetic resources, and to better decipher the whole genome information of T.mongolica, the second-generation high-throughput sequencing technology of genome survey analysis was used as the method, and bioinformatics method was used to estimate the genome information such as heterozygosity, repeat sequence and GC content of T.mongolica respectively. The results showed that the genome size of T. mongolica was 1 079.25 Mb, the corrected genome size was 1 065.84 Mb, and the heterozygosity rate was 0.76%, the percentage of repetitive sequences was 75.25%, and the GC content was 33.57% respectively. After the initial assembly of T. mongolica genome 3 502 126 contigs were obtained, totaling 682 Mb, with an N50 of 187 bp. It was hypothesized that T. mongolica genome belonged to a homo-tetraploid complex genome, which was difficult to assemble by whole-genome sequencing. Due to the high heterozygosity of T. mongolica, the third-generation high-throughput sequencing technology(single-molecule sequencing) combined with chromatin region capture technology could be used subsequently, which was expected to finally obtain a high-quality whole-genome map of T. mongolica.

    Physiology and Ecology
    Effects of N addition on Root Exudates and Their Mediated Nutrient Rransformation Processes in a Betula albosinensis Burk Forest in Southwest China
    Zhenggang XU, Hang XU, Xiutao PENG, Shijun LIANG, Rong LIU, Shanghua LUO, Juan XIAO
    2023, 43(2):  194-206.  doi:10.7525/j.issn.1673-5102.2023.02.005
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    At present, we still lack a deep understanding of the response direction and amplitude of root exudate flux and related ecological consequences to different nitrogen(N) deposition levels. In order to reveal the difference in the effects of different N addition treatments on root exudate C flux and its mediated soil nutrient transformation process, the typical Betula albosinensis Burk forest in the mountainous area of southwest China was used as materials, and different nitrogen deposition levels were simulated by in-situ N addition experiment(control group, 0 kg·hm-2?a-1); low nitrogen treatment, 25 kg·hm-2?a-1; High nitrogen treatment, 50 kg·hm-2?a-1 respectively. The results showed that: (1)N addition significantly reduced the C input rate(the average root exudation rate per unit root biomass decreased by 14.87% under low nitrogen(N25))and annual C input flux of root exudates(about 45.01% reduction under low nitrogen condition)(P<0.05), and high N treatment had stronger inhibition effect on root exudates C input. (2)N addition significantly inhibited soil N mineralization rate and related microbial extracellular enzyme activities(P<0.05), and significantly reduced its rhizosphere effect. In conclusion, N deposition significantly inhibited the root exudates C flux and its mediated soil nutrient transformation process, and this inhibition effect increased with the increase of N deposition level. The results could enrich the understanding of carbon-nutrient cycling in forest under global climate change.

    Different Nitrogen Forms on the Photosynthetic Characteristics and Growth of Fraxinus mandshurica and Quercus mongolica
    Tingting LI, Liu YANG, Xiaoxia LI, Yisong WANG, Xiuwei WANG
    2023, 43(2):  207-217.  doi:10.7525/j.issn.1673-5102.2023.02.006
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    To explore the differences in the effects of on the growth and photosynthetic characteristics of tree seedlings, and their adaptation strategies to different nitrogen forms, the one-year seedlings of Fraxinus mandshurica and Quercus mongolica were used as materials, and three nitrogen fertilizer forms were applied: nitrate N, ammonium N and organic N. Two-way ANOVA was used to analysis the effect and interaction of nitrogen form and tree species on the growth and photosynthetic. Spearman rank correlation was used to analysis the correlation between growth index and photosynthetic index. The results were as follows, the effects of nitrogen form treatments, tree species and their interactions on the growth and physiological indexes of seedlings were significant(P<0.05) respectively. Photosynthesis rate and growth were significantly different between the two tree species in nitrogen forms(P<0.05). The organic N treatment group was more beneficial to the growth of Q. mongolica, than the control group and other nitrogen form treatment groups; the growth indexes of F. mandshurica in the three nitrogen forms treatment groups were significantly higher than those in the control group(P<0.05), but there was no significant difference in the growth indexes of F. mandshurica between the nitrogen form treatments(P>0.05). Through the correlation analysis of the growth and physiological indicators of F. mandshurica and Q. mongolica, there was a significant positive correlation between the photosynthetic indexes of F. mandshurica, but the correlation between photosynthetic indexes and leaf nitrogen content was not significant(P>0.05). The growth amount was significantly positively correlated with the light compensation point, light saturation points and dark respiration rate(P<0.05); the maximum net photosynthetic rate of Q. mongolica was significantly positively correlated with the stomatal conductance(P<0.01). The correlation between other photosynthetic indexes was not significant (P>0.05), the maximum net photosynthetic rate was significantly positively correlated with leaf nitrogen content(P<0.001), and high growth was negatively correlated with the maximum net photosynthetic rate and stomatal conductance relationship(P<0.01 and P<0.05). Nitrogen forms and tree species and their interaction have significant effects on seedling growth and photosynthetic characteristics. Different tree species have different response strategies under different nitrogen forms. The organic nitrogen is more conducive to the growth of Q. mongolica, but nitrate nitrogen has a more obvious effect on the growth of F. mandshurica. The result of this study provides reference for the cultivation of appropriate nitrogen fertilizer in Northeast China.

    Effects of Combined Application of N and P on Stoichiometric Ratio of N, P and K of Pinus yunnanensis Seedlings after Stumping
    Zhuangyue LU, Zhenxin YANG, Chaofan ZHENG, Xi LUO, Nianhui CAI, Yulan XU
    2023, 43(2):  218-230.  doi:10.7525/j.issn.1673-5102.2023.02.007
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    To understand the effects of combined application of N and P on the stoichiometric characteristics of N, P and K in different organs(root, stem, leaf and sprout) of Pinus yunnanensis seedlings, the seasonal variation characteristics of the stoichiometric ratio of ω(N)∶ω(P), ω(N)∶ω(K) and ω(P)∶ω(K) in different organs(root, stem, leaf and sprout) of P. yunnanensis seedlings were analyzed, and the seedlings of P. yunnanensis treated with different N and P were sampled and measured, and different fertilization experiments were carried out by using 3×3 regression design with 2 factors and 3 levels of N and P. The effects of combined application of N and P on the stoichiometric ratio of N, P and K in roots, leaves, stems and sprouts of P. yunnanensis after stumping were studied. The results showed that P. yunnanensis seedlings had no rule for the distribution of nutrient elements in different organs after flat stubble, but showed rich variation. With the change of fertilization season, ω(N)∶ω(P) decreased gradually in roots, stems and sprouts, and decreased first and then increased in leaves, but the overall difference was not significant. There were some differences in the effects of single application of N, P and combined application of N and P on the growth of P. yunnanensis seedlings. In general, the combined application of N and P was more beneficial to promote the growth of seedlings, and treatment No.5(N1P1) showed extremely significant(P<0.01). The N, P and K stoichiometric ratios of all organs of seedlings were mainly influenced by the N×P interaction, followed by N and P was the least. The positive and negative correlations between ω(N)∶ω(P) and ω(N)∶ω(K) remained unchanged except in roots and leaves were changed, where the correlation between ω(N)∶ω(P) and ω(N)∶ω(K). The correlations between ω(N)∶ω(P) and ω(P)∶ω(K), ω(N)∶ω(K) and ω(P)∶ω(K) changed with seasonal changes in fertilizer application and the correlation coefficients decreased, regulated by P and K, respectively. Stumping changed the content of nutrient elements in the plant, and different fertilization treatments made significant differences in the stoichiometric characteristics of N, P and K in different organs of P. yunnanensisP<0.01). The combined application of N and P could effectively alleviate the limiting effect of single application of N and P on plants, and the nutrients was in a balanced state, and meet the needs of plant growth.

    Population Structure and Dynamic Characteristics of Three Endangered Mangrove Species from Genus Sonneratia
    Mengwen ZHANG, Cairong ZHONG, Xiaobo LÜ, Zanshan FANG, Cheng CHENG
    2023, 43(2):  231-241.  doi:10.7525/j.issn.1673-5102.2023.02.008
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    In order to illuminate population structures and dynamics of endangered mangrove species from genus Sonneratia,and provide a fundamental understanding and scientific basis for the protection and restoration of endangered mangrove species, the natural populations of three endangered mangrove species including Sonneratia × hainanensisS. × gulngaiS. ovata were conducted as the research object, and the characteristics of population structure were described by establishing a static life table and drawing a population survival curve, and their future development trends were quantitatively described by population dynamic prediction and time series analysis respectively. The results showed that: (1)The populations structure of S. ovata was increasing type, while both S.× hainanensis and S. × gulngai were the declinated type due to the lack of young individuals. (2)The population survival curves of three endangered species showed the Deevey-Ⅱ type, and the mortality and disappearance curves of all populations showed the same trend, and showed a wavy line with the increase of age class. Both S.× hainanensis and S. × gulngai encountered obstacles in the aging stage, while S. ovata encountered bottlenecks in the development of young individuals. (3)The renewability of S.× hainanensis and S. × gulngai population was poor, and the population numbers would gradually decline in the future. The population of S. ovata had a good recovery potential, and the population number would increase gradually. However, if the population number of S. ovata decreased with the increase of age class, it might lead to the phenomenon of age class fault. (4)Human activities led to fragmentation of the original habitat, resulting in a series of environmental factors(light, salinity, tide, etc.) unsuitable for seed germination and seedling growth, which greatly inhibited the natural regeneration of the endangered species. Therefore, it would be recommended to step up efforts to protect the endangered natural populations in situ, optimization of ex situ conservation strategies and scientific implementation of field regression, carried out artificial assisted breeding to break through the problems of breeding, and ensured the normal renewal of the population.

    Response of Leaf Functional Traits and their relationships to Seasonal Changes in Four Acer Species
    Yang LIU, Liying XU, Tongchao WEI, Lanyi SHEN, Dounan LIU, Yue LIU
    2023, 43(2):  242-250.  doi:10.7525/j.issn.1673-5102.2023.02.009
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    Four species of AcerA. mandshuricumA. tataricum subsp. ginnala., A. saccharumA. pictum subsp. mono)on Mudanjang were selected as materials in spring, summer and autumn, respectively, and the seasonal variation trend of leaf traits(e.g. leaf thickness(TL), stomata length(LS), stomata width(WS), stomata density(DS), leaf vein density(DV), specific leaf area(ASL) and pigment content) were analyzed, and the relationship between pigments and leaf morphological traits in different seasons were explored respectively. The result showed that: (1)Four kinds of Acer species showed higher TL, lower ASL and DS in summer, higher ASL and DV, lower TL in autumn. (2)The chlorophyll a and b of four Acer species were higher in summer, and the pigment content decreased in autumn. Their seasonal variation ranges were chlorophyll a 77.40%-98.80%, chlorophyll b 85.60%-99.53%, and carotenoids 4.29%-78.52%. (3)Pigment was closely related to leaf morphological traits. Under seasonal dynamics, pigments were positively correlated with ASLDS and DV, and negatively correlated with TLLS and WSP<0.05), but the correlations were slightly different in different seasons. The leaf was formed different construction strategies in response to climatic conditions in different seasons in four color species. The variation of leaf functional traits reflected the trade-off mechanism of colored-leaf plants adapting to seasonal changes.

    Effects of Pulp and Buried Depth on Seed Germination and Seedling Growth of Armeniaca vulgaris
    Yingying TANG, Chuanchao GUO, Dang SHI, Nanlin JIANG, Zheng XU, Liqiang LIU
    2023, 43(2):  251-260.  doi:10.7525/j.issn.1673-5102.2023.02.010
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    In order to explore the response of seed germination and seedling growth of Armeniaca vulgaris to pulp and buried depth, and provide theoretical reference for natural regeneration and seedling cultivation of A. vulgaris, the seed germination and seedling growth of A. vulgaris were studied by seeds of two kinds of pericarp structure(pulp and no pulp) at different buried depths(14 gradients from surface to 18.0 cm). The results showed that pulp and buried depth significantly affected seed germination, seedling growth and quality(P<0.05). The buried depth <3.0 cm was not conducive to seedling, and the germination ability and seedling growth decreased with the increase of buried depth when buried depth >6.0 cm, 3.0-6.0 cm was the optimal buried depth, and the germination of seeds with no pulp was better than that of seeds with pulp, the germination rate, germination index, seedling rate and vigor index increased by 37.18 %, 3.88 %, 37.18 % and 26.59% respectively, seedling height, basal diameter, leaf number, root-shoot ratio and seedling quality index increased by 36.99%, 7.48%, 68.69%, 20.61% and 14.29%, respectively. The germination ability and seedling growth were significantly higher than those of pulpy seeds(P<0.05). The seed germination and seedling growth indexes of pulp and no pulp seeds were significantly negatively correlated with buried depth(P<0.05). The results showed that the no pulp seed had a certain promotion effect on seed germination and seedling growth of A. vulgaris, and the germination of seeds of A. vulgaris was optimal at the buried depth of 3.0-6.0 cm.

    Effects of Single-household and Multi-household Management on Soil Physicochemical Properties and Plant Diversity in Alpine Meadow
    Fengling YIN, Minxia LIU, Cheng LIU, Mingxing WANG, Ke XI
    2023, 43(2):  261-271.  doi:10.7525/j.issn.1673-5102.2023.02.011
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    Grassland biodiversity played an important role in grassland ecosystem stability. In order to reveal the influence mechanism of soil physical and chemical properties on plant diversity of different management methods in grassland, and clarify the changes of species diversity and functional diversity, and the sample plots in the single-household management pasture(SMP) and multi-household management pasture(MMP) of plant community in Alpine Meadow of Gannan were surveyed respectively. The results indicated that: (1)The Margalef index, Simpson index, and Shannon-Winener index of the plant communities under MMP were significantly higher than those under SMP, while the Pielou index was not significantly different under different grazing management methods. (2)Under different management methods, the soil water content, the soil total nitrogen and the soil total phosphorus under MMP were significantly higher than those under SMP(P<0.05) respectively; the soil conductivity and soil pH under SMP were higher than those under MMP; with the deepening of soil layer, the soil water content, the soil total phosphorus, the soil total nitrogen, the soil organic carbon, and the soil conductivity were higher respectively, however the soil pH had no significant difference in the different soil layer. (3)The functional richness, functional evenness index, and functional dispersion under MMP were higher than those under SMP respectively, and the difference between SMP and MMP were significant(P<0.05). (4)The correlation analysis showed that: the plant species diversity and functional diversity were significantly positively correlated with the soil water content, the soil total nitrogen, and the soil phosphorus, the soil conductivity and soil pH were significantly negatively correlated with plant species diversity and functional diversity. The redundancy analysis showed that: the effect of soil physicochemical properties on plant diversity was more significant under MMP, and the correlation between soil physicochemical properties and plant diversity were higher at the 0-10 cm soil layer. The soil total nitrogen and the soil organic carbon were significant influencing factors of plant diversity under SMP and the soil total nitrogen and the soil total phosphorus were significant influencing factors of plant diversity under MMP.

    Responses of Biomass Allocation to Population Density and Soil Water in Abutilon theophrasti at Different Growth Stages
    Kenian LINGHU, Shu WANG
    2023, 43(2):  272-280.  doi:10.7525/j.issn.1673-5102.2023.02.012
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    To reveal the strategies of plants in dealing with biotic and abiotic envrionmental factors through investigating responses of biomass allocation to soil water and population density at different growth stages, in this experiment, we subjected plants of an annual herbaceous species of Abutilon theophrasti to treatments of water addition and no addition(control). Within each treatment, low, medium, and high densities were set up under field conditions, before measuring dry mass of root, stem, lamina, petiole and reproductive(flower and fruit) organs at day 20 and 50 of growth, to explore how biomass allocation of A. theophrasti respond to density and water addition, and effects of growth stage. Results showed at day 20, in water-added soil, compared to that at low density, medium density increased root mass ratio by 19.4% and root/shoot ratio by 21.5%, but decreased leaf mass ratio by 34.4%, with no response to density in biomass allocation in no-water-added soil(control). At day 50, in controlled soil, high relative to low density reduced total biomass by 63.5%; in both water treatments, high relative to low density reduced root/shoot ratio and root mass ratio, but increased stem mass ratio, with total mass and allocations of other organs unaffected. Results suggest that the additon of water is more likely to promote the active response(increase) of root mass allocation to increased density at early stage, and mitigated passive responses(decrease) of total biomass at later stage. The responses of biomass allocation to density may depend on the strength of intraspecific interactions, and at the early stage moderate level of interactions among plants will more likely lead to facilitation underground, promoting the active responses of roots, and moderate interactions among plants at medium density can also promote active responses of roots to water addition. Growth stage can modify the strength of plant-plant interactions via affecting plant size, and further affect the responses of biomass allocation to density and water availability.

    Molecular biology
    The Mechanism of H2S Signal and Ca2+ Regulating Stomatal Movement in Medicago sativa
    Xuefeng HAO, Chunxia KANG, Yanxi PEI, Zhuping JIN
    2023, 43(2):  281-287.  doi:10.7525/j.issn.1673-5102.2023.02.013
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    To explore the role of H2S signal in regulating stomatal movement in alfalfa and the relationship between H2S and Ca2+ during this process, wild type and the calcium transporter mutants of Medicago truncatula were used as experimental materials, and the transcriptional level, cellular level and physiological level were studied respectively, and the expression levels of related genes were compared by qRT-PCR, the content of Ca2+in vivo was detected by fluorescent probe, the content of H2S was measured by electrode method, and the stomatal aperture was observed by microscope respectively. The results showed that compared with the wild type, the content of H2S in the mutant NF3011 and NF2734 decreased significantly; the H2S signal inhibited the expression of calcium transporter encoding gene MTR_6g027580, the exogenous physiological concentration of H2S fumigation could induce stomatal closure of Medicago truncatula, and the combination of treatment with LaCl3, Ca2+ channel blocker, had no effect on stomatal movement of wild type, but opposite in mutant; the concentration of Ca2+ in guard cells was measured by fluorescence probe, which were consistent with the change law of stomatal aperture. In conclusion, the content of Ca2+ in guard cells of leaves is induced by H2S, whose stomatal aperture become smaller at the same time. In this process, the change of intracellular Ca2+ concentration mainly depend on Ca2+ transporter, and small partly depend on Ca2+ channel. The results of this study not only enrich the mechanism of H2S signaling in theory, but also have the potential to be applied to alfalfa production and other crops.

    Function Analysis of the Transcription Factor PsnbZIP1 of Populus simonii×P. nigra in Response to Salt Stress
    Shixian LIAO, Yuting WANG, Liben DONG, Yongmei GU, Fenglin JIA, Tingbo JIANG, Boru ZHOU
    2023, 43(2):  288-299.  doi:10.7525/j.issn.1673-5102.2023.02.014
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    To reveal the function of transcription factor PsnbZIP1 from Populus simonii × P. nigra under abiotic stresses, P.simonii × P. nigra was used as material, and the PsnbZIP1 transcription factor gene was cloned with an ORF length of 432 bp, and the molecular mechanism of PsnbZIP1 under salt stress was analyzed. The expression pattern of PsnbZIP1 in P. simonii × P. nigra was analyzed under 150 mmol·L-1 NaCl by q-PCR, it was found that the expression of the gene increased rapidly. The PsnbZIP1 was predicted to be a hydrophilic unstable protein without trans-membrane structure but with signal peptide by bioinformatics analysis. The sub-cellular localization of the gene was observed by Agrobacterium mediated transient expression in tobacco. The results showed that the gene was a nuclear localization protein. It was confirmed by Y2HGold yeast competent cells that the gene had no transcriptional activation activity in yeast. The analysis of the promoter sequence of the PsnbZIP1 gene showed that the promoter contained auxin response elements, ABA response elements, light response elements and seed-specific cis-acting regulatory elements respectively, which might play a role in plant growth and development and response to stress.The promoter also included the MYB binding site and MYBHv1 binding site involved in drought induction, indicating that the gene was likely to interact with some of MYB involved in drought induction.

    Response Analysis of Transcription Factor PsnbHLH162 Gene in Populus simonii × P. nigra under Salt Stress and Low Temperature Stress
    Senyao LIU, Fenglin JIA, Qing GUO, Gaofeng FAN, Boru ZHOU, Tingbo JIANG
    2023, 43(2):  300-310.  doi:10.7525/j.issn.1673-5102.2023.02.015
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    To reveal the role of transcription factor PsnbHLH162 of Populus simonii × P. nigra under abiotic stresses, and to explore the signal transduction process of genes in plants, the signal transduction process of this gene in plants is explored to provide the theoretical basis for the acquisition of excellent stress-resistant tree species in the future. In this experiment, PsnbHLH162 gene was cloned and obtained from P. simonii × P. nigra as material, and the target gene and promoter were analyzed by bioinformatics; and the function of genes in response to abiotic stresses was analyzed by fluorescence quantitative PCR. The results showed that the cDNA of PsnbHLH162 gene was 537 bp, and the N-terminal of the gene contained a highly conserved HLH domain, and the encoded protein might be a stable hydrophilic protein without trans-membrane region, localized in the nucleus and had no transcriptional activation activity. The promoter region contained a variety of ABA-responsive, auxin-responsive, light-responsive and circadian elements, confirming that this gene participated in abiotic stress response. The results of fluorescence quantitative PCR showed that under salt stress, the gene expression in root tissue was the highest compared with stem and leaf tissue; under low temperature stress, gene expression in stem tissue was the highest compared with leaf and root tissue. It was found that the expression of PsnbHLH162 could be induced by salt and low temperature in plants.

    Reproductive biology
    Flowering Biological Characteristics and Breeding System of the Rare and Endangered Plant of Sinojackia microcarpa
    Changrui TAI, Kai ZHAO, Yanfang YANG, Yan WU, Wei ZHAI, Yuewei TONG
    2023, 43(2):  311-320.  doi:10.7525/j.issn.1673-5102.2023.02.016
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    In order to illustrate the flowering characteristics and sexual reproduction of the rare and endangered plant Sinojackia microcarpa, the morphological characteristics of flower, flowering dynamics, pollen ovule ratio(P/O), stigma receptivity, pollen viability, bagging experiment, pollinator insects and pollinator frequency were investigated respectively. The results showed that: (1)the hybridization index(OCI) was four, the flowering period was 5-7 d, and the flowering period of the population lasted 20 d. Pollen to ovule ratio was 4 093.21±498.56. The pollen viability was the highest on the third day after flowering(76.21%), but the lowest on the seventh day after flowering(18.37%). The most suitable period of stigmas was on the second day after flowering. (2)The bagging result showed that: there were some self-incompatibility and no apomictic reproduction in S. microcarpa. Pollinators were necessary for the reproductive process of S. microcarpa, and cross-pollination could improve the rate of fruit and seed setting. There were seven species, five families and three orders in the visiting insects of S. microcarpa. The main pollinators were Xylocopa appendiculataBombus sp.,Vespa sp.,Apis ceranaEpisyrphus balteatus. The average pollinator frequency of Bombus sp. was (8.67±0.21) times per hour. Further research on the biological characteristics of flowering and breeding system of this species would be helpful to further explore the mechanism of its endangerment, and provided theoretical basis and reference for future studies on rare and endangered plants.