林业科学研究

Thermal Stress Photosynthetic Response of Picea pungens

OUYANG Fang-qun, CUI Xia, ZHANG Hui, DENG Jun-yu, SHI Qing-song, LI Yu-ling, SUN Meng

Objective The continuous global warming will be detrimental to the growth of Picea pungens. Studying the growth and photosynthetic response mechanism under high temperature stress would provide a reference for the introduction and cultivation of P. pungens. Methods Three temperatures were set at 45, 50 and 55 ℃, and treated for 6 hours using P. pungens seedlings. Among them, three different durations of 12,18 and 24 hours were also set under 45 ℃ treatment, and room temperature was used as a control. The growth phenotype, relative water content and chlorophyll fluorescence parameters of P. pungens seedlings after treatment, 7 and 28 days of recovery were studied, and the effects of high temperature and stress duration on the growth and photosynthesis of P. pungens were analyzed. Result The growth of P. pungens could basically be restored after 6 hours treatment at 45 ℃, while those treated at 50 and 55 ℃, their needles turned yellow, withers and falls, accompanied by the decrease of relative water content. The fluorescence parameters photochemical efficiency for photosystem I (Y(I)), relative electron transfer rate of photosystem I (ETR(I)), non-photochemical energy dissipation due to donor-side restriction (Y(ND)), non-photochemical energy dissipation due to receptor-side restriction (Y(NA)), photochemical efficiency for photosystem II (Y(II)), the relative electron transfer rate of photosystem II (ETR(II)), PSII maximum light energy conversion efficiency (F_v/F_m) and the maximum quantum yield of electron transport between PSII and PSI (φE_O) were significantly lower than those treated and controlled at 45 ℃. Although the phenotypic change could not be seen after treatment at 45 ℃ for 6, 12, 18 and 24 hours, it was found that the needles continued to lose water and turn yellow at 12 hours and 18 hours during the recovery period, and the whole needles turned yellow after 24 hours treatment, basically dried up and fell off, and the relative water content of the needles was the lowest. When recovering for 28 days, φEo at 18 and 24 hours was almost 0. Conclusion P. pungens can withstand high temperature treatment at 45 ℃ for 6 h, but it is not resistant to high temperature of 50 ℃ and 55 ℃. The seedlings with a high temperature treatment time of 45 ℃ for more than 12 hours will suffer severe water loss and dry needles, which will have a significant impact on the photosynthetic characteristics and make it difficult to resume normal growth. More >

Analysis and Prediction of Eucalyptus urophylla × E. grandis in Response to Thinning and Pruning

ZHANG Shi-tao, OUYANG Lin-nan, CHEN Shao-xiong, YANG Jia-qi

Objective To explore the effects of thinning and pruning with different intensities on the growth of Eucalyptus urophylla × E. grandis, the BP neural network model was developed to predict the growth of E. urophylla × E. grandis under thinning and pruning treatment, for providing theoretical guidance for efficient management technology of E. urophylla × E. grandis. Method Taking 20%, 40% and 60% thinning and 38.18%, 42.39% and 48.18% Based on the E. urophylla × E. grandis in the Southern National Forest Seedling Demonstration Base with treatments of 20%, 40% and 60% thinning and 38.18%, 42.39% and 48.18% pruning, the stand growth indexes were investigated for 7 years after treatment, and the effects of different thinning and pruning treatments on the growth increment of the stands were analyzed. Furthermore, BP neural network was used to predict the response of cumulative increment to thinning and pruning. Root-mean-square error, Kappa and Pearson correlation coefficient were used to compare the prediction effect of models, and the optimal model was determined. Results Thinning treatment promoted the growth of DBH, crown width and tree volume, but did not promote the growth of height and wood production. The increment of DBH and tree volume was the highest in the stands with 60% thinning intensity, the increment of crown width was the highest in the stands with 20% thinning intensity, and the increment of height was the highest in the control stands. Pruning promoted the growth of DBH, but did not promote the growth of height and wood production. DBH increase was the highest in the stands with 38.18% pruning intensity. The treatment with 60% thinning and 48.18% pruning was conducive to the growth of E. urophylla × E. grandis. Both thinning and pruning could promote the right-sided distribution of diameter class, but the effect of pruning was not significant. In summary, the BP neural network model with 4 nodes in the hidden layer had the lowest root-mean-square error and the highest Kappa value and r value. Conclusion Thinning and pruning can significantly promote the growth of E. urophylla × E. grandis and the right-sided distribution of diameter class. The combination of high-intensity thinning and pruning is more beneficial to the growth of E. urophylla × E. grandis plantation and the cultivation of large diameter wood. The reasonable BP neural network model can accurately predict the promotion effect of thinning and pruning on stand growth and is an excellent model for predicting stand growth. More >

Effect of UAV-LiDAR Point Density on Estimation Accuracy of Forest Inventory Attributes

ZHOU Mei, LI Chun-gan, LI Zhen, YU zhu

Objective Point density is a key factor affecting the cost and efficiency of data acquisition and pre-processing of unmanned aerial vehicle (UAV)-based light detection and ranging (LiDAR), and it is helpful to explore the effects of point density on the estimation accuracy of UAV-LiDAR-based forest inventory attributes to optimize the technical schemes for UAV-LiDAR forest applications. Methods This study focused on the planted Masson pine and Eucalyptus forests. The original UAV-LiDAR point cloud with a density of 247 points∙m⁻² was reduced by 40%, 20%, 8%, 4%, and 2% according to the percentage of the total point reduction algorithm to obtain six plot-level UAV-LiDAR datasets, including five sets of reduced point densities. Each dataset was pre-processed separately, including point cloud classification, ground point filtering, digital elevation model (DEM) generation, point cloud height normalization, and UAV-LiDAR-derived metric extractions. The same multiplicative power formula was used for estimating the same forest parameters (stand volume, basal area, mean height, and average diameter at breast height) for the same forest type, and each dataset was used to calibrate the model. Then, the differences in the goodness-of-fit statistics of the models were compared and analyzed based oncoefficient of determination (R²), relative root square error (rRMSE), mean prediction error (MPE), and the differences in the mean of the estimates and the UAV-LiDAR-derived metrics between the reduced point density datasets and the original point density dataset were statistically analyzed. Results The results indicated that the model accuracy remained essentially the same when the original point density was reduced to 100, 50,..., 5 points∙m⁻², and there were no statistically significant differences (p≥0.05) in the estimates of forest inventory attributes between the reduced point density datasets and the original point density dataset. There were basically no statistically significant differences (p≥0.05) in UAV-LiDAR-derived metrics between the reduced point density datasets and the original point density dataset. Conclusion In the application of UAV lidar forest resource inventory and monitoring, the point cloud density can be as low as 5 points∙m⁻². However, the results of this experiment still need to be verified by acquiring point cloud data at different densities at different flight altitudes. More >

Response of Nitrogen Mineralization in Soil Aggregates to Changes in Soil Moisture and Temperature in the Three Gorges Reservoir Area's Typical Plantation

CHEN Tian, CHENG Rui-mei, XIAO Wen-fa, ZENG Li-xiong, SHEN Ya-fei, WANG Li-jun, SUN Peng-fei, ZHANG Meng, LI Jing

Objective Rising temperatures and precipitation have become challenges. In order to investigate the effects of climate change on soil nitrogen (N) dynamics in forests of the Three Gorges Reservoir area and to provide a basis for predicting changes in soil nutrient cycling in this area and enhancing forest productivity. Method The soil was sieved into large macroaggregates, coarse aggregate, small macroaggregates, and microaggregates (particle sizes: 8000-2000, 2000-1000, 1000-250, and <250 μm) in a mixed plantation of Pinus massoniana-Quercus variabilis. Differences in net N conversion of aggregates were observed at soil moisture of 40%, 60%, and 80% of the maximum water holding capacity in the field (named 0.4 FCW, 0.6 FCW, and 0.8 FCW), and at temperatures of 5°C, 15°C, 25°C, and 35°C using indoor incubation methods. Results The levels of soil organic matter (SOM), total N and microbial biomass carbon (C), and nitrogen were higher in small-size aggregates with larger specific surface areas, while available phosphorus (P) was significantly lower. The rates of net nitrification and net N mineralization of aggregates gradually increased with decreasing particle size, with net nitrification contributing more than 85% of net N mineralization. The rates of net nitrification and net N mineralization of aggregates first increased and then decreased with the increase of soil water moisture and temperature, and the maximum values appeared at 0.6 FCW and 25 ℃. The overall net ammonification, net nitrification, and net N mineralization rates of aggregates of different particle sizes were most sensitive to temperature increase at 0.60 FCW and 15°C/25°C. By developing a quadratic equation, the optimum soil moisture and temperature for the net ammonification rate were 0.70 FCW and 23.0°C, and the optimum soil moisture and temperature for the net nitrification and net nitrogen mineralization rates were 0.58 FCW - 0.60 FCW and 24.5°C - 27.5°C. Conclusion The physical structure of aggregates protects organic N from decomposition in the plantation in the Three Gorges Reservoir area. Rising temperatures and precipitation promote net N transformation in the soils, which is conducive to improving the N supply capacity of the soil; However, there is a risk of soil organic matter, N loss, and P limitation over the long term, so that monitoring and fertilizer measures can be carried out if necessary. More >

Promoter Functional Analysis of the Key Gene PsDFR Involved in Paeonia suffruticosa Anthocyanin Biosynthesis

ZHOU Lin, YUAN Meng, Qi Yu, ZHANG Meng-jie, WANG Yan

Objective To analyze the cis-acting element and activity of the tree peony anthocyanin biosynthetic key gene PsDFR promoter for further research on its function and regulation mechanism involved in tree peony flower coloration. Method The genomic DNA extracted from the petals of tree peony ‘Hei Hua Kui’ was used as a template. PsDFR promoter was isolated by genomic walking method. The cis-acting elements of promoter were analyzed and predicted through Bioinformatics online software. Five different length of deletion fragments were fused with GUS gene to construct promoter-reporter vectors, and then were transiently expressed in tobacco leaves. The activities of deletion promoters and their response to different stress treatments such as Abscisic acid (ABA), Methyl jasmonate (MeJA) and light were analyzed by GUS staining and GUS activity assay. Result A 1 687 bp sequence of PsDFR promoter was isolated. The results of bioinformatics analysis showed that the promoter contains multiple cis-acting elements associated with light signals, hormone response, stress response, and tissue-specific expression, indicating that the expression of PsDFR may be regulated by various signals such as light signaling, plant hormone and stress. GUS staining and quantitative analysis of GUS activity showed that GUS activities decreased gradually with decrease of the length of PsDFR promoters, and the region of -1 623 bp to -916 bp played an important role on the activity of the PsDFR promoter. The GUS activities were inhibited significantly by MeJA or dark treatment, and were induced obviously after light restoration. And core regulation region involved in ABA-response might be located between -443 and -76 bp. Conclusion PsDFR promoter contains multiple cis-acting elements associated with light signals, hormone response, stress response, and tissue-specific expression. Its activity is positively regulated by light and negatively regulated by MeJA. The region of -1 623 bp to -916 bp is important for the activity of the PsDFR promoter, and -443 and -76 bp is the core region in response to ABA treatment. This study provides a reference for further revealing the regulatory mechanism of PsDFR response to environmental signals involved in tree peony flower coloration. More >

Functional Conservation Existed in PagKNAT2/6a and PagKNAT2/6b During Xylem Development

LI Hai-yang, ZHAO Li-zi, ZHAO Yan-qiu

Objective To analyze the regulatory mechanism of PagKNAT2/6a in poplar dendritic development and the functional conservation of PagKNAT2/6a and PagKNAT2/6b in xylem development. Methods Gene sequence alignment analysis was carried out by using related software; Gene expression pattern analysis was performed by experiments such as GUS staining and real-time quantitative (qRT-PCR) of transgenic plants, and then stem anatomy analysis was also performed; Finally, genes related to secondary wall synthesis (such as cellulose synthesis-related genes CESA4, CESA7A, CESA7B, etc.; Hemicellulose synthesis-related genes GUX1a, GUX1b, PARVUS; Expression analysis and regulatory mechanism of lignin synthesis-related genes COMT, CAD, LAC4, etc) were explored. Results The sequences of PagKNAT2/6a and PagKNAT2/6b were highly similar, and they were expressed in different tissues of ‘84K’, showing higher expression levels in poplar stems, stem tips and young leaves. Stem anatomy analysis of transgenic plants abnormally expressing PagKNAT2/6a showed that PagKNAT2/6a overexpression inhibited xylem development compared with wild type. At the same time, qRT-PCR analysis showed that PagKNAT2/6a gene related the expression of genes related to secondary wall synthesis and affected xylem development. Conclusion PagKNAT2/6a and PagKNAT2/6b both negatively regulate xylem development and have functional conservation. More >

Cloning and Yeast Expression Function Identification of High Expression XsKCS7 Gene in Xanthoceras sorbifolium Seed

LIANG Chong-jun, LI Lin-kun, HU Zhen-hua, ZHANG Wei, XU Hui-hui, WANG Li-bing

Objective To explore the key genes of regulating nervonic acid biosynthesis in Xanthoceras sorbifolium seeds. Method This study analyzed the expression pattern of the 3-ketoesteryl-CoA synthase (3-ketoacyl-CoA synthase, KCS) gene family in seeds at different developmental periods according to the combined transcriptome of the reference genome. Gene XsKCS7 was cloned by RT-PCR, and was analyzed by Bioinformatics analysis of XsKCS7 protein. And the XsKCS7 gene was transformed into Saccharomyces cerevisiae to identify the gene function. Result The expression level of XsKCS7 gene in seeds of X. sorbifolium was much higher than other KCS genes. The open reading frame of XsKCS7 was 1,512 bp, encoding 503 amino acids, havd three typical conserved domains of KCS family "GMGCSA", "FGNTSSSS" and "GSGFKCNSAVW", and a close relationship with the homologous gene of Hevea brasiliensis,at 67.62%. XsKCS7 heterologous transformation of Saccharomyces cerevisiae regulated the synthesis of erucic acid and nervonic acid. Conclusion : XsKCS7 gene is a key gene that regulates the synthesis of erucic acid and nervonic acid in seeds of X. sorbifolium. More >

Journal Introduction

Forestry Science Research is a comprehensive academic journal of forestry science sponsored by the Chinese Academy of Forestry Science. The main task is to timely reflect the latest research results, academic papers and reports, scientific and technological trends and information of forestry science with the Chinese Academy of Forestry as the main body, to promote academic exchanges at home and abroad, to carry out academic discussions, to prosper forestry science and to better serve China's forestry construction. The main contents are: forest seeds, seedling raising and afforestation, forest plants, forest genetic breeding, tree physiology and biochemistry, forest insects, resource insects, forest pathology, forest microorganisms, forest birds and animals, forest soil, forest...

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Niche and Interspecific Association of Dominant Species in Phoebe sheareri Natural Community

LU Yun-feng, YANG An-na, WANG Hao, LIU Wei, ZHANG Jun-hong, LOU Lu-huan, TONG Zai-kang

doi: 10.12403/j.1001-1498.20230245

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Objective In order to explore the interspecific correlations and the stability of Phoebe sheareri natural community. Method Based on field sample survey, the ecological niche characteristics and interspecific associations of dominant species in the arbor layer and shrub layer of P. sheareri community were studied by through species composition, important value, niche breadth, niche overlap index, variance ratio method, and χ2 test. Result The important value, Levins niche breadth, and Shannon-Weaver niche breadth of P. sheareri were the largest in the investigated communities, indicating that both the resource utilization degree and competitive advantage were strong. The dominant species in the arbor layer showed an overall insignificant positive association（VR = 1.247, χ20.95（12） > W > χ20.05（12））, while the shrub layer showed an overall insignificant negative association（VR = 0.674, χ20.95（36） > W > χ20.05（36））, indicating that the stability of the arbor layer was higher than that of the shrub layer. The χ2 test result showed that the positively associated species pairs were more than the negatively onepairs, and the ratio of positive to negative association of arbor layer and shrub layer were 1.8∶1 and 1.5∶1, respectively. The majority of species pairs were not significantly associated, indicating that the ecological characteristics of most dominant species in the P. sheareri community were relatively consistent. Conclusion The P. sheareri community was is relatively stable. However, appropriate artificial tending practices should be carried out to promote the natural regeneration of these P. sheareri populations.

Seasonal Permafrost Degradation Characteristics in Southern Part of Greater Khingan Mountains under Climate Change

SUN Yi-chen, WEI Jiang-sheng, SHU Yang, ZHAO Peng-wu, QI Gui-ping, ZHANG Jing

doi: 10.12403/j.1001-1498.20230337

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Objective Seasonal permafrost degradation directly changes water recharge at the beginning of the growing season, which in turn affects regional forest health. At present, the degradation of permafrost in Southern Part of Greater Khingan Mountains is still unclear, especially the degradation characteristics under climate change. Method : In the long-term experimental forest of Saihanwula National Nature Reserve in Inner Mongolia, environmental factors such as air temperature, soil temperature, and volumetric soil water content were observed from 2014—2022 to analyze the characteristics of permafrost degradation in forest seasons. Result : The temperature in Southern Part of Greater Khingan Mountains rose in shortly. The rise rate of annual average temperature was 0.42 ℃·10 a⁻¹ in 1998—2022, which was larger 23.5% of the rate of 0.34 ℃·10 a⁻¹ in 1973—1997, in Southern Part of Greater Khingan Mountains. It is particularly significant that the average temperature during the freeze-thaw period (i.e., November to June) rose faster with the rate of 0.46 ℃·10 a⁻¹. The freeze-thaw pattern of soil was characterized by top-down unidirectional freezing and unidirectional melting; The freezing rate and thawing rate became faster with increasing soil depth, reaching a maximum in the 40～80 cm soil layer (freezing rate 2.23 cm·d⁻¹, thawing rate 4.50 cm·d⁻¹). Seasonally frozen soil continued to degrade, with the observed maximum freezing depth reduced from 80 cm to 40 cm. The freeze-thaw period was significantly shortened, the start of freezing was delayed, and the complete thaw time was advanced, resulting in a shortening of the annual freeze-thaw period by 15.21%. Applying the freeze-thaw multiple linear regression model established in this paper, the contribution of elevated air temperature accumulation to seasonal permafrost degradation in the study area was more than 90%. Conclusion : In the Southern Part of Greater Khingan Mountains, permafrost degradation is mainly characterized by shortening of the freeze-thaw period, and warmer temperatures are the main driver of seasonal permafrost degradation, making it necessary to monitor changes in seasonal permafrost in the future for better forest management.

Characterization of Nutrient Stoichiometry Variability in Pleioblastus amarus Leaves from Different Subtropical Regions and its Environmental Drivers

ZHANG Jing-run, ZUO Ke-yi, GUO Zi-wu, FAN Li-li, LIN Hua, HU Rui-cai, CHEN Shuang-lin

doi: 10.12403/j.1001-1498.20230364

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Objective The study aimed to explore the impact of geographical differentiation on the stoichiometric characteristics of Pleioblastus amarus leaves and identify their primary environmental drivers. Method The C, N, P content, and stoichiometric ratio of P. amarus leaves from three different regions: Qianshan County, Anhui Province; Longyou County, Zhejiang Province; and Shaxian District, Fujian Province were explored. Pearson correlation analysis, LSD difference analysis, and structural equation modeling were employed to investigate the correlation between these characteristics and environmental factors. Result The results indicated that the contents of C, N, and P in P. amarus leaves decreased with increasing latitude, while the ratios of C∶N, C∶P, and N∶P showed an overall upward trend. Notably, P. amarus leaves from Qianshan County exhibited significantly lower concentrations of C, N, and P than those from Longyou County and Shaxian District. Moreover, the ratios of C∶N, C∶P, and N∶P were significantly smaller in Qianshan County than those in the other two regions. Additionally, the study found that as the age of the culms increased, the concentrations of C, N, and P decreased, while the ratios of C∶N and C∶P increased. There was no significant change observed in the N to P ratio with different ages. Pearson correlation analysis revealed that the annual mean temperature and soil chemical properties (such as total nitrogen, total phosphorus, total potassium, hydrolyzed nitrogen, available phosphorus, available potassium, organic matter, etc. ) significantly influenced the stoichiometric characteristics of P. amarus leaves. On the other hand, mean annual precipitation and soil physical properties had little effect on the stoichiometric characteristics of P. amarus leaves. The results of the structural equation model indicated a significant positive correlation between climatic factors, soil factors, and leaf stoichiometry characteristics, with similar effects. Conclusion This suggests that the variation in leaf stoichiometry due to geographical differentiation may be attributed to the combined effect of climate and soil factors. Among these factors, the annual average temperature, soil hydrolyzable nitrogen, soil total phosphorus, and soil available potassium are the main indicators affecting the stoichiometric variation of leaves.

Comprehensive Selection of 29-year-old for Provenances/ Families of Teak (Tectona grandis Linn.f.) in Southwestern Yunnan

LIANG Kun-nan, ZHANG Rong-gui, HUANG Gui-hua, CHU Yong-xing, WANG Xian-bang, SHI Wen-ge

doi: 10.12403/j.1001-1498.20230324

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Objective Through the comprehensive evaluation of the adaptability, growth and form quality traits of teak(Tectona grandis Linn.f.) forests (provenance / family) of early and 29-year-old established in southwestern Yunnan, the purpose is to select the superior provenances / families of teak with strong adaptability, fast growth and excellent form quality for the local region. Method Thirty-four provenances and families of teak were collected from China and abroad. Using a completely random block design with (2 × 2) plant plots and 8 replicates to establish trial plantation, the conservation rate and growth difference of the early 2-8 year old and 29-year old trees were investigated, analyzed and compared. The conservation rate, the growth and quality traits of dominant trees of 29-year old provenances/families were analyzed by principal component analysis, and excellent provenances/families were evaluated comprehensively. Result There was no significant difference in the preservation rate between the 2-8-year-old teak provenances/families in the early stage, while the difference in the preservation rate between the 29-year-old provenances/ families was extremely significant. However, the differences in growths and quality traits between 2-8-year-old or 29-year-old provenances / families were extremely significant. The average tree height, average DBH and average tree volume of 2-8-year-old best provenances / families were 1.38-1.91 times, 1.63-2.18 times and 3.82-5.17 times of the worst growing ones, respectively. The average tree height, average DBH, average tree volume, stem straightness and trunk height of 29-year-old dominant trees from the best provenances were 1.84 times, 1.87 times, 4.84 times, 2.18 times and 12.89 times of those from the worst provenances, respectively. Greater yield-increasing benefits can be obtained through the selection of excellent provenance / family. The preservation rate and growth traits of dominant trees of 29-year-old provenances/families were significantly correlated with the growth traits of 4-8-year-old dominant trees. The stem straightness of dominant trees of 29-year-old provenances / families was significantly correlated with the growth traits of dominant trees, and the tree height of dominant trees was significantly correlated with the average tree height and individual volume growth of dominant trees. The cumulative contribution rate of the first three principal components of 29-year-old provenances / families preservation rate, growth and form quality traits was 97.63%. According to the comprehensive score in the first three principal components of the provenances / families, seven excellent provenances / families （8410、8603、8407、8602、85131、1007 and 7564^#）were selected according to the selection rate of 20%. Conclusion The genetic gains of dominant tree height, DBH, individual volume, stem straightness and trunk height of the seven provenances / families selected at 29 years old are 7.92%, 9.39%, 14.74%, 7.06% and 12.29%, respectively. Among them, provenance 8410 from Yunnan Longchuan Forest Farm and provenance 8603 from Hainan Jianfengling are more suitable for local growth.

Comprehensive Evaluation and Index Screening of Salt Tolerance for Three Afforestation Specie Seedlings in China

GAN Hong-hao, GONG Shuai, LIU Hao, CHU Jian-min

doi: 10.12403/j.1001-1498.20230319

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Objective To study the differences in salt tolerance among the Melia azedarach, Ulmus pumila and Robinia pseudoacacia seedlings and to select the evaluation indexes of salt tolerance. Method Based on the one-year-old seedlings of M. azedarach, U. pumila and R. pseudoacacia, the effects of different NaCl concentrations (0, 100, 200 and 300 mmol·L⁻¹) on the seedling biomass, physiological and biochemical indexes were analyzed. Result (1) NaCl stress inhibited the biomass of M. azedarach, U. pumila and R. pseudoacacia seedlings, decreased the relative water content of leaves and increased the electrolyte permeability. (2) The contents of chlorophyll a and b in R. pseudoacacia decreased significantly with the increase in NaCl concentration. But the chlorophyll content in M. azedarach and U. pumila seedlings only decreased significantly under 300 mmol·L⁻¹ NaCl treatment. The photosynthetic parameters Pn, Gs, Ci and E decreased under NaCl stress in the 3 tree seedlings, but the stomatal limitation and water use efficiency increased. Meanwhile, the concentrations of free proline and soluble protein, as well as the activities of CAT and APX in roots and leaves also increased. (3) NaCl stress changed the ion balance in the roots and leaves of the 3 tree seedlings. The Na⁺ concentration in roots and leaves and K⁺ concentration in leaves of the 3 tree seedlings significantly increased under NaCl stress, but the concentration of K⁺ in roots, as well as the concentrations of Mg²⁺ and Ca²⁺ in roots and leaves had differential changes. Conclusion The seedlings of U. pumila have the strongest salt tolerance, followed by M. azedarach, R. pseudoacacia. The concentrations of free proline and soluble protein in roots, CAT and APX activities in roots and leaves, Ca²⁺ in roots and Na⁺ in leaves are highly correlated with salt tolerance of the 3 tree seedlings, which can be used as the evaluation indexes of salt tolerance.

Effects of Different Exogenous Substances on Rooting, Basal Physiology and Biochemistry of Quercus mongolica Cuttings

ZHONG Ming-xia, AI Wan-feng, YUAN Xin, HUANG Yi-he, WEI Jun, WANG Yu-tao, LU Xiu-jun

doi: 10.12403/j.1001-1498.20230362

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Objective Cutting propagation is an important way to propagate excellent seedlings, and the application of suitable exogenous substances can promote rooting of cuttings. The rooting of Quercus mongolica cuttings is difficult. Exploring the effects of different concentrations of exogenous substances and their combine applications on the rooting of Quercus mongolica softwood cuttings can provide technical support for large-scale propagation by cutting propagation. Method Using rapid dipping or soaking methods, different concentrations of indole butyrate potassium (IBA-K), rooting powder (ABT₁), K599 Agrobacterium rhizogenes, propiconazole (PCZ), and their combination were used to treat cuttings. The rooting rate, callus rate, rooting number, root length, nutrient content, enzyme activity, and changes in endogenous hormone content of cuttings were measured. Result When different exogenous substances were used separately, the rooting rate of K599 Agrobacterium rhizogenes (OD₆₀₀ = 0.8) was the highest after soaking for 30 minutes, reaching 24.71%. After soaking in 50 μM PCZ for 2 hours, the root callus rate of cuttings was the highest, reaching 43.62%. For other exogenous substances alone, the rooting effect of cuttings was poor. When different combinations of exogenous substances were used, 50 μmol·L⁻¹ PCZ soaking for 2 hours combined with K599 Agrobacterium rhizogenes (OD₆₀₀ = 0.8) soaking for 30 minutes significantly improved the rooting rate of Quercus mongolica cuttings, reaching 36.37% for rooting and 51.14% for callus. The average number of roots and root length were 2.25 and 5.72 cm, respectively. In addition, the results indicated that the use of PCZ can accelerate the consumption of soluble sugars and proteins during the rooting process of cuttings, promote the activities of peroxidase (POD) and polyphenol oxidase (PPO), increase the content of IAA during the induction period of adventitious roots, and increase the IAA/ABA and IAA/ZR ratios. Conclusion The combined application of PCZ and Agrobacterium rhizogenes K599 can significantly improve the rooting rate of Quercus mongolica softwood cuttings. Slow consumption of nutrients (soluble sugars, proteins), weak activity of antioxidant enzymes (PPO, POD), and low content of IAA may be the reasons of the difficulty in rooting of Quercus mongolica cuttings. PCZ has an important inhibitory effect on this, and can play an important role in difficult rooting species such as Quercus mongolica cuttings.

Selection of Reference Genes for Gene Expression Analysis in Seed Development of Xanthoceras sorbifolium Bunge

LI Lin-kun, LIANG Chong-jun, NING Chu-long, ZHANG Wei, JIANG Guo-Wei, ZHANG Xin, WANG Li-bing

doi: 10.12403/j.1001-1498.20230291

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: Objective : To assess the suitability of the ACT gene for gene expression analysis in seed development of Xanthoceras sorbifolium, and to identify the most stable reference genes for gene expression analysis in X. sorbifolium. Method : In this study, four mathematical algorithms (ΔC_T, BestKeeper, NormFinder, geNorm) were carried out for evaluating the expression stability of 12 candidate reference genes based on the web-based tool RefFinder. Result : The RefFinder result showed that the gene PP2A performed the best, followed byTip41, EF-1α,18r, UCE, β-TUB, UBQ, α-TUB, CYP, SAM, ACT, and GADPH at the different seed development stages in X. sorbifolium , and the gene also had the highest score, followed by Tip41, CYP, 18r, UBQ, SAM, EF-1α, UCE, GADPH, α-TUB, ACT, and β-TUB at various tissues. Conclusion : PP2A and Tip41 are the two most stable reference genes for gene expression analysis in X. sorbifolium.

Functional Characteristics of Rhizosphere Soil Microbial Communities of Relict Plant Glyptostrobus pensilis in Different Seasons

ZHANG Chen, ZHOU Liu-ting, WANG Yan-yan, LIN Rui-yu, WU Ze-yan

doi: 10.12403/j.1001-1498.20230221

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Objective To explore the structure and function of rhizosphere microbial community of Glyptostrobus pensilis and its seasonal variation. Methods PCR-DGGE and Biolog-ECO microplate methods were used to determine the soil physicochemical properties, structure and function of rhizosphere microbial community of G. pensilis in different seasons, and the intrinsic patterns of rhizosphere microecological factors were analyzed by principal component analysis and redundancy analysis. Result The dominant bacterial in the rhizosphere microbial community of G. pensilis were Alphaproteobacteria, Acidobacteria and Deltaproteobacteria, and the dominant fungi was Sordariomycetes. Rhizosphere microbial biomass content and microbial diversity in the soil of G. pensilis are the highest in summer. Carbon metabolism of rhizosphere microorganisms in the summer was the largest, followed by autumn, spring, and winter. Available nitrogen may be the main factor driving changes in the functional diversity of carbon metabolism in rhizosphere microbial communities. Conclusion The diversity and carbon metabolism ability of rhizosphere microbial community of G. pensilis are the best in summer and the worst in winter. Seasonal factors significantly affect the structure and function of rhizosphere microbial community, and the fluctuation caused by seasonal factors should be fully considered in the future related research.

Optimization and Application of Transient Transformation System of Larix kaempferi

XING Jun-xia, ZANG Qiao-lu, YE Zha-long, ZHANG Chen-yi, CHENG Dong-xia, QI Li-wang, YANG Ling, LI Wan-feng

doi: 10.12403/j.1001-1498.20230390

[Abstract](883)

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Abstract:
Objective To optimize an Agrobacterium-mediated transient transformation system with Larix kaempferi embryogenic callus. Methods The embryogenic callus of Larix kaempferi cultured in liquid medium for 7 days was used as the receptor material, and pCAMBIA1305.1 vector carrying β-glucuronidase (GUS) was used for transient transformation. Based on the expression level and enzyme activity of GUS, the optimal infection solution concentration, infection time and co-culture time were screened. The activity of Larix kaempferi scarecrow-like 6 (LaSCL6) promoter was analyzed with the screened transformation system. Results After transient transformation, the expression of GUS was obvious. When the concentration of infection solution was 0.2, the infection lasted for 5 minutes, and the co-culture time was 72 hours, GUS expression was the highest, with -2.274 2. When the concentration of infection solution was 0.05, the infection lasted for 5 minutes, and the co-culture time was 72 hours, GUS enzyme activity was the highest with 25.728 6 U/L. The activity of LaSCL6 promoter was 1.55 times higher than that of CaMV35S promoter Conclusion In view of the expression level and enzyme activity of GUS, transformation efficiency is high when the concentration of infection solution is 0.05, the infection time is 5 minutes, and the co-culture time is 24 hours, which can be used for efficient transformation of embryogenic callus of Larix kaempferi.

Root Exudates Improving Soil Phosphorus Availability: A Review

HUANG Yu-xuan, You Xin, ZHANG Lin-ping, WU Fei, ZHANG Yang, HUANG Shao-hua

doi: 10.12403/j.1001-1498.20230477

[Abstract](299)

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Abstract:
Phosphorus is an essential mineral nutrient element that plays an important role in plant growth and development. Although most soils have sufficient total phosphorus reserves, most of the organic and inorganic phosphorus in the soil exhibit low solubility and low available, leading to the extremely low soil available phosphorus content. Plant root exudates are important mediators linking energy, matter and information transfer at the interface between the plant root system and the soil. They can directly regulate the activation of soil ineffective phosphorus, and also can indirectly improve the bioavailability of soil phosphorus by recruiting inter-root microorganisms. In this paper, the potential mechanisms of different root exudates to improve soil phosphorus effectiveness are elucidated, and how root exudates can recruit inter-root microorganisms to promote soil phosphorus activation is discussed in the light of the existing studies at home and abroad. Meanwhile, the future research direction is also prospected. It will provide a theoretical basis for analyzing the mechanism of efficient plant phosphorus utilization and cultivating phosphorus efficient varieties.

Sugar Accumulation and the Relevant Enzymes Activities of Camellia gauchowensis

LIU Zhen, CHEN Rui-fan, SHEN Chun-hui, XI Ru-chun, DENG Xiao-mei

doi: 10.12403/j.1001-1498.20230398

[Abstract](234)

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Abstract:
: Objective To study the characteristics of sugar accumulation in various source-sink organs during the growth and development of Camellia gauchowensis and its relationship with the enzymatic activities related to sugar metabolism for providing a basis for further improving the theory of sugar accumulation in characteristic oil tea camellia varieties in the South China region. Method We employed the ¹³C isotope pulse labeling method to determine the ¹³C content in various source-sink organs at different developmental stages of C. gauchowensis. We also measured changes in non-structural carbohydrate (NSC) content, sugar component characteristics, and related enzyme activities in the respective organs during the corresponding periods. Result 1) After the stabilization of the transport of ¹³C-labeled photosynthates, during the early developmental stages, these products were primarily accumulated in the eaves, while in the later stages, the seed kernels gradually became the central location for assimilate distribution and accumulation. 2) The soluble sugar content in various organs was mainly observed in the order of peels > seeds > leaves, while starch content showed the order of leaves > seeds > peels. 3) The activities of SPS and SS-II were positively correlated with the soluble sugar content in leaves, peels, and seeds. B-AI primarily played a role during the later stages of development, with peak activities in seed kernels occurring in August and October. In leaves, NI served as the primary sugar-converting enzyme, with activity ranging between 50 and 60 U·g⁻¹. In seed kernels, the activities of S-AI and NI were roughly similar, with S-AI primarily acting during the early developmental stages, while NI was more active during the later stages of development. Conclusion In C. gauchowensis, during the early stages of development, photosynthates primarily accumulate leaves of the source organ,. As fruit grows, the seed kernels gradually becomes the central location for assimilate distribution. Regarding sugar accumulation, during the early developmental stages, seed kernels primarily accumulates fructose and glucose, while in the later stages of development, they mainly accumulate sucrose. In the later stages of development, the sucrose transported to the peels will be decomposed into fructose and glucose, and the peels continues to thicken and extend, and continue to complete lignification. At this stage, there is intense competition for nutrients between the peels and seeds, resulting in the phenomenon of thick peels and large fruit size. The functions of SPS and SS-II complement each other and simultaneously influence sugar accumulation in C. gauchowensis, with SS-II being the key enzyme for sugar accumulation. This may be the primary reason for differences in sugar content among various source-sink organs. Sugar accumulation in C. gauchowensis is regulated comprehensively by sugar metabolism-related enzymes. NI serves as the primary conversion enzyme in the leaves, while S-AI and NI play roles in seed kernels during the early and late developmental stages, respectively. In peels, sucrose conversion primarily depends on S-AI. B-AI primarily functions in the later stages of development but with relatively low activity and limited conversion capacity.

Identification and Expression Analysis of PtoS1-bZIP Subfamily in Populus tomentosa

WU Jiang-ting, JIA Chen-lin, LUO Zhi-bin, DENG Shu-rong

doi: 10.12403/j.1001-1498.20230333

[Abstract](392)

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Abstract:
Objective To identify S1-bZIP subfamily members in Populus tomentosa and analyze the expression profiles of PtoS1-bZIP genes in different tissues in response to abiotic stress. Method Members of PtoS1-bZIP subfamily were systematically analyzed using bioinformatic approaches. Real-time PCR was performed to explore the expression patterns of PtoS1-bZIP genes in different tissues, as well as under different hormonal or abiotic stress treatment. Result A total of ten intron-lacking PtoS1-bZIP genes were identified in the genome of Populus tomentosa, which were distributed to eight distinct chromosomes. According to phylogenetic analysis, PtoS1-bZIP subfamily members were divided into three sub-clades, designated as Clades I to III. 12 pairs of fragment replicates were identified in the genome of Populus tomentosa. Cis-acting element prediction showed that the promoter regions of PtoS1-bZIP genes were rich of various regulatory elements involving light, hormone or abiotic stress response. qRT-PCR analysis revealed that the members of PtoS1-bZIP subfamily were specifically expressed across different tissues. The majority of PtoS1-bZIP genes in the first and second clades were upregulated under ABA and drought treatments, while expression levels were downregulated under salt treatment. In contrast, all of the PtoS1-bZIP members in the third clades were upregulated under ABA, drought, and salt treatments. Conclusion In the genome of Populus tomentosa, ten PtoS1-bZIP genes are identified and divided into three clades. The expression of major PtoS1-bZIP genes in the first and second clades were induced by drought stress and inhibited by salt stress. The expression of members in the third clades were induced by both drought and salt stress. It indicates that different clades of PtoS1-bZIP genes may have functional differentiation, which play different roles in response to abiotic stresses. Our results lay a foundation for further investigation of the biological functions of PtoS1-bZIP genes and their molecular mechanisms involved in regulating stress resistance of poplars.

Dynamics of Soil microbial Groups in Pinus tabulaeformis Plantation in Response to Stand Structure Adjustment

FA Lei, PEI Shun-xiang, DU Man-yi, MA Shu-min, WU Sha, WU Di, WANG Hai-xia, LI Jia-lin, XU Ji-huang

doi: 10.12403/j.1001-1498.20230389

[Abstract](567)

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Abstract:
Objective We explore the response mechanism of soil microbial community structure dynamics to the interference of stand structure adjustment in order to evaluate the impact of management treatment on the ecosystem of Pinus tabulaeformis Plantation. Methods Based on Pinus tabulaeformis plantations in Zhongtiao Mountain, Shanxi Province, we explored the group composition and diversity of soil microorganisms under the stand structure adjustment through the high-throughput sequencing technology to analyze the composition and structure, diversity of soil microbial community and its correlation with environmental factors. Results The results showed that stand structure adjustment could reduce the pH value of soil and the content of soil nutrients. The dominant flora of soil microorganisms did not change significantly. Proteus, actinomycetes and Acidobacteria were the dominant bacterial groups in the soil of Pinus tabulaeformis plantation, while the dominant fungal groups were Ascomycetes, Basidiomycetes and Mortierella. The richness of soil microorganisms in Pinus tabulaeformis plantation increased significantly after adjustment, but the difference was not significant. RDA analysis showed that pH, total nitrogen, soil organic matter and available nitrogen were the main factors driving changes in soil microbial community structure. Conclusion The treated Pinus tabulaeformis plantation is still in the disturbance recovery period. The microbial community structure is similar to that of the control treatment, but is more abundant in Pinus tabulaeformis plantation after stand structure adjustment, which improves the proportion of nitrogen fixing bacteria in the soil. The increase in Proteobacteria and Basidiomycota leads to soil microorganisms shift towards organic matter decomposition.

Diversity and Community Stability of Understory Vegetation in the Pinus massoniana Forest after Transformation in Thousand-island Lake Area

ZHOU Xiu-bin, XU Yu-hua, LIU Min, LUO Chao, PAN Wen, LI Sheng

doi: 10.12403/j.1001-1498.20230348

[Abstract](519)

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Abstract:
Objective Transforming Pinus massoniana coniferous forest into broadleaved forest is beneficial to improving the structure and function of forest ecosystem and has significant influence on the regeneration and succession of understory vegetation. The analysis of the diversity and community stability of understory vegetation after forest transformation can provide reference for sustainable forest management. Method In this study, based on the four types of stand transformation (i.e., I thinning and promoting regeneration, II thinning and planting broadleaf trees, III clear cutting and promoting regeneration, clear cutting and IV clear cutting and planting broadleaf trees) of Pinus massoniana forests in Thousand-island Lake Forest area, Chun’an county, and control treatment (V no-transformation forest )), the species composition, diversity and community stability of understory vegetation were investigated. The relationship between understory species composition and stand factors was analyzed, and the relationship between species diversity and community stability was also explored. Result The difference of understory dominant species among different stands was lower in shrub layer than in herb layer. The understory species diversity in control group was significantly lower than that in transformed stand (P < 0.05) and the species diversity of herb layer in type IV was significantly higher than that in other types (P < 0.05). The stand factors could explain about 40% of understory species variation and had higher effect on the species composition of herb layer than that of shrub layer. Among these, the canopy density was the most important factor. In the early stage of stand transformation, the understory community stability in mode V was the best, followed by I, II, III, and IV. The community stability of shrub layer had low correlation with species diversity, while the stability of herb layer was negatively correlated with species diversity (P < 0.05). Conclusion In the early stage of broad-leaf transformation of P. massoniana forest in Thousand-island Lake area, the diversity of herbaceous layer was significantly improved mainly by reducing canopy density, but the stability of understory vegetation community was low under clear cutting treatments. Therefore, considering vegetation diversity and community stability, appropriate thinning and tending measures can promote the development of understory vegetation in P. massoniana forest.

Transcriptome analysis of Populus in response to Fusarium solani (Mart.) Sacc inoculation

HAO Xin-yi, WANG Zhe-shu, FAN Zhi-bin, WANG Li-juan

doi: 10.12403/j.1001-1498.20230458

[Abstract](463)

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Abstract:
Objective To study the differentially expressed genes, related signaling pathways and metabolic pathways between poplar- Fusarium solani (Mart.) Sacc interactions, and screen the key genes of poplar against Fusarium. solani (Mart.) Sacc inoculation for laying a foundation for further revealing the molecular mechanism of this disease. Methods The roots of 2-month-old seedlings of 84K were inoculated with 1 × 10⁷ spores·mL⁻¹ of F. solani (Mart.) Sacc spore solution. Zero-hour (control group), 48 h and 72 h (inoculated groups) after inoculation, root tissues were taken for transcriptome sequencing to explore genes related to poplar response to F. solani (Mart.) Sacc infection. Result (1) Compared with the control group, 8939 and 8246 DEGs (Differentially Expressed Genes) were detected in 48 h and 72 h inoculated samples, respectively. (2) GO analysis found that the differentially expressed genes were mainly enriched in single-organism process, response to stimulus, carbohydrate metabolism process, biological regulation and response to hormone. (3) KEGG pathway enrichment analysis showed that the DEGs were significantly enriched in glycolysis/gluconeogenesis, carbon metabolism, plant hormone signal transduction and phenylpropanoid biosynthesis. (4) The expressions of 21 genes in the SWEETs family of poplar were induced by F. solani (Mart.) Sacc. Ethylene receptor ETR, and the main components of the ethylene signaling pathway EIN3, ERF1, ERF2 were up-regulated. The expression levels of key enzyme genes involved in lignin synthesis including CCR, 4CL, C3’H and COMT were significantly increased. Conclusion Poplar may respond to the invasion of F. solani (Mart.) Sacc by regulating sugar metabolism and transport, activating the ethylene signaling pathway, promoting lignin accumulation, and thickening cell wall.

Decomposition Characteristics of Fresh Residues of Pleioblastus Amarus in Different in-forest Environments

LIN Da-xue, ZHAO Hou-ben, HUANG Chun-hua, XU Wei-hua, LI Zhaojia, Zhou Zhi-ping

doi: 10.12403/j.1001-1498.20230342

[Abstract](554)

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Abstract:
Objective To study the decomposition process of fresh residues of Pleioblastus amarus (Keng) keng and its influential factors, predict the changes in processes of ecosystem material cycling in bamboo forests after being mechanically damaged by extreme climatic events, and assess the impacts of the disaster on the function of forest carbon sinks for providing a basis for the scientific management of forests after the disaster. Methods Based on the secondary forests, where P. amarus expanded greatly after clearcutting, in the Nanling area of Guangdong Province, two treatments including removal of understory bamboos (RB) and control (CK) were set uo to generate distinct in-forest environments, and the decomposition characteristics of fresh residues from various organs of P. amarus were studied using the decomposition bag method. Results The decomposition process of fresh residues of each organ of P. amarus could be divided into two stages, rapid mass loss in the early stage (first 2 months) and slow decomposition in the later stage (last 24 months). The average mass loss rate of each organ in the early stage was in the order of leaves (51.2%) > twigs (31.7%) > roots (24.4%) > culms (16.6%), and there were significant differences (P<0.05) among all organs, with a significantly lower mass loss rate of leaves in RB environment than that of CK. The average mass loss rate of each organ at the later stage was in the order of twigs (40.3%) >leaves (29.1%) > culms (28.1%) > roots (19.6%), and there were significant differences among the organs except for leaf and culm. The mass loss rate of branches in RB environment was significantly higher than that of CK, while the mass loss rate of roots was significantly lower than that of CK. The Olson decomposition model could well fit the decomposition processes of various organs., The average decomposition coefficient (k) of leaves (0.891) was the largest, followed by the twigs (0.554), culms (0.249), and roots (0.242). There were significant differences of the k among all organs except for culms and roots, and the k of leaves in RB environment was significantly lower than that of CK. The period of 50% decomposition (T_0.5) of each organ was in the order of culms (2.48 a) > root (2.44 a) > twigs (0.97 a) > leaves (0.51 a), with roots and culms significantly higher than twigs and leaves, and the T_0.5 of root in RB environment was significantly higher than that of CK. The decomposition period (T_0.95) of each organ was in the order of roots (12.81 a) > culms (12.12 a) > twigs (5.22 a) > leaves (3.22 a), with roots and culms significantly higher than twigs and bamboo leaves. Under RB environment, the T_0.95 of culms and roots was significantly lower and higher than that of CK, respectively. The correlation coefficient between the substrate quality of various organ and decomposition indexes was generally higher in the early stage than in the later stage, and higher in the CK than in the RB environment. Among them, the correlation coefficients between carbon (C), potassium (K), C/nitrogen (N), C/phosphorus (P) and the decomposition indexes were relatively small; N, P, and N/P were positively correlated with decomposition rate, and lignin/N was negatively correlated with decomposition rate. Conclusion Decomposition of fresh residues of P. amarus is characterized by a rapid weight loss in the early stage and a slow decomposition in the later stage. Leaves have the fastest decomposition rate, followed by twigs and culms, and roots are the slowest. Among the substrate qualities of various organ, N, P, N/P, and lignin/N have significant impacts on the decomposition rate, in particular in the early stage of decomposition. Removal of understory bamboo can slow down the decomposition of leaves and roots, accelerate decomposition of culms and twigs, and attenuate the effects of substrate quality on decomposition rates.

Effects of Foliar Spray of Selenite on Metabolome in Leaves of Torreya grandis Seedlings

CHEN Zhen-sheng, LI Ai-hua, DU Shi-ping, HUANG Pei-geng, XU Xiu-huan, NING Bo-lin, LI Wen

doi: 10.12403/j.1001-1498.20240012

[Abstract](673)

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Abstract:
Objective To investigate the effects of foliar spray of selenite on metabolome in the leaves of Torrey grandis seedlings and changes in levels of secondary metabolites in the leaves. Method Sodium selenite of 100 μg·L⁻¹ was sprayed to the leaves of 2-year-old seedlings of T. grandis at an interval of 15 d. Fifteen d after the second spraying, one-year-old leaves were harvested for metabolome analysis. Result The results showed that there were 909 differential metabolites between treatment group and control under positive ionization mode, with 69 metabolites of significant changes (27 metabolites up-regulated and 42 metabolites down-regulated). Under negative ionization mode, 433 differential metabolite occurred between treatment group and control, with 43 differential metabolites of significant changes (11 metabolites up-regulated and 32 metabolites down-regulated). Some metabolites beneficial to human health increased significantly in the treated leaves of T. grandis seedlings, such as plantagoside (increasing 2.827 times as control), ligustilide (increasing 2.524 times) , 6-sialyllactose (increasing 2.021 times), and azilsartan (increasing 1.931 times). Conclusion The results indicate that selenite foliar application on the leaves of T. grandis can increase biosynthesis of beneficial metabolites and accumulation in their leaves.

The Physiological Response of Populus alba to Drought Stress

XU Hui, XUE Yuan

doi: 10.12403/j.1001-1498.20230472

[Abstract](826)

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Abstract:
Objective In this study, Populus alba was used to detect the effect of drought stress on growth and development, which provided reference for the molecular mechanism of the response to drought stress in woody. Method The seedlings of Populus alba about five weeks were treated with drought stress, the growth state and drought stress-related physiological indicators and genes were record and detected to reveal the resistance of Populus alba to drought stress. Result The results showed that the water content of leaves decreased significantly and stomatal aperture became smaller after 8 days of drought treatment; meanwhile ROS increased significantly, ABA accumulated in the body, and the growth-related hormone IAA content decreased, drought stress-related genes were upregulated. Conclusion By detecting the tolerance of Populus alba to drought stress from multiple perspective, the growth of their seedlings is significantly inhibited after drought treatment for 8 days, which indicates that watering timely is necessary.

Effects of Different Thinning Retention Densities on Branch Growth of Chinese Fir Plantations

WANG Jia-qi, MA Dong-xu, CHEN Kuai-ming, LAN Wei-li, LIN Kai-min

doi: 10.12403/j.1001-1498.20230334

[Abstract](981)

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Abstract:
Objective To study the effects of different thinning retention densities on the branch growth of Chinese fir plantations, and to provide scientific theoretical basis and technical support for directed cultivation of Chinese fir knotless-wood. Method Based on the 9-year-old Chinese fir plantations in Guanzhuang state-owned forest farm, Shaxian County, Fujian province, three kinds of thinning retention densities (1200 trees·hm⁻²(thinning intensity: 67% , L) , 1800 trees·hm⁻²(thinning intensity: 51% , M) and 2250 trees·hm⁻²(thinning intensity: 27% , H) were set up. In the fifth year after thinning, standard trees were selected in different plots to study the effect of thinning treatments on the branch growth of Chinese fir. Result 1)The total number of branches, the number of branches below 8 m, the number of branches above 8 m, the number of dead branches, the number of living branches all under L treatment were the largest, followed by treatment M and H, and the percentage of dead branches under treatment H were the largest, followed by treatment M and L. 2)The basal diameter increased with the decrease of thinning intensity which showed L > m > H, and there was significant difference between L and H (P < 0.05) , which indicated that the lower retention density was more conducive to the branch growth. 3)There was a significant linear correlation between the basal diameter and the length of the living branch, while correlation between the basal diameter and the length of the dead branch was small. 4)The basal diameter, branch length, the number of dead branches and the number of living branches increased with the increase of vertical height, while the basal diameter and the length of living branches and the branching angle of H and M decreased with the increase of vertical height of the trunk. 5)The basal diameter, branch length and branching angle of dead and living branches were larger in the southern region (90～225 °) than in the northern region, but the number of branches was larger in the eastern region (0～180 °) than in the western region. Conclusion The thinning intensity should be adjusted according to different cultivation purposes. The lower retention density can inhibit the growth of basal diameter and number of branches, thus reducing the size and number of knots and improving the wood quality. In this study, the retention density1800 trees/ha is more suitable to cultivate knotless large-diameter timber.

Investigation and Analysis on Host Species and Their Resistance Substances to Bacterial Bark Canker of Populus × euramericana

LI Yong, CHANG Ju-pu, GUO Li-min, SUN Shang, YANG Xu-qi, PIAO Chun-gen

[Abstract](7647)

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Abstract:
Objective To investigate and analyze the host species of bacterial canker of Populus × euramericana, the disease-resistant varieties and the possible disease-resistant substances they contain. Method The host of the pathogen and the resistant varieties were determined by field investigation and inoculation tests. The content of active substances in the bark of disease-resistant and susceptible varieties was analyzed by HPLC. Result The hosts of bacterial pathogen of P. × euramericana canker are P. deltoides, P. × euramericana and Salix matsudana. P. × euramericana cl. 'Zhonglin 46', P. deltoides cl. '2025', P. × euramericana cv. '2001', P. deltoides cl '313', P. deltoides 'Zhonghe-1' and P. deltoides '16-09' were highly susceptible to the bark canker disease; P. × euramericana 'Yukang 1' and P. deltoides '16-10' were highly resistant varieties, P. deltoides '131', P. deltoides '03-59', P. deltoides '02-212' and P. deltoides '03-34' were resistant varieties. Hybrid willows and Salix babylonica are resistant to the pathogen, and Salix × aureo-pendula can be affected, but do not cause serious disease. The HPLC analysis showed that the contents of catechol, benzoic acid and chlorogenic acid in the bark of resistant and highly susceptible poplar varieties were significantly different. The catechol and catechin increased when the hosts were infected by Lonsdalea populi. Conclusion In this study, the host species of bacterial canker of P. × euramericana are determined, and resistant and highly susceptible poplar varieties are screened. It is showed the catechol and catechin are important compound for host to defense the pathogen infection. The results will be helpful to the control of the bacterial disease of poplar.

Effects of Castanopsis kawakamii Forest Litter on Seed Germination of Pinus massoniana

JIA Mei-hua, WANG Zhe, LIU Jin-fu, JIN Meng-ran, HE Zhong-sheng, XING Cong, SHI You-wen, SHEN Cai-xia

[Abstract](9398)

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Abstract:
Objective To understand the effect of litter of Castanopsis kawakamii natural forest on the competitive intensity of regeneration of Pinus massoniana. Method The allelopathic effects of litter extract of natural forest with different concentration and decomposition degree on seed germination and radicle growth of P. massoniana were studied. Result (1) The main factor affecting the germination of P. massoniana seeds was the degree of litter decomposition. Compared with the blank control, the litter of undecomposed layer and fully decomposed layer had no significant effect on the germination of P. massoniana seeds; the semi-decomposed layer inhibited the germination rate and germination index and promoted the germination potential. (2) The main factors affecting the growth of radicle were the concentration and action time of litter extract, and the effect of undecomposed layer on the whole radicle growth period of P. massoniana seeds was enhanced with the decrease of concentration, but increased with the decrease of concentration, and the promoting effect was the strongest at the concentration of 1 ≤ 100, and the effect of semi-decomposition layer was promoted by low concentration and high concentration, and the intermediate concentration was inhibited by the undecomposed layer. The fully decomposition layer showed promoting effect as a whole, and the promoting effect decreased with the decrease of concentration. (3) Correspondence analysis showed that different decomposition degree-concentration had no significant effect on seed germination of P. massoniana, but had significant correlation with radicle growth. Conclusion The result proves that the litter extract of different decomposition degree has a weak promoting or inhibiting effect on the seed germination of P. massoniana, promotes the growth of radicle at low concentration, and promotes the regeneration of P. massoniana, which will intensify the interspecific competition in the forest, and lead to the inhibition of the natural regeneration of C. kawakamii.

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