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    20 January 2023, Volume 43 Issue 1
    Taxonomy
    Nutlet Morphology and Micromorphology of Carex sect. Paniceae (Cyperaceae) and Its Taxonomic Significance
    Fang HE, Yifei LU, Yongdi LIU, Wenke CHU, Xiaofeng JIN
    2023, 43(1):  1-8.  doi:10.7525/j.issn.1673-5102.2023.01.001
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    Nutlet morphology and micromorphology of 27 species with four varieties of Carex sect. Paniceae were observed under scanning electron microscopy(SEM). The results showed that:(1)The nutlet shape of all samples(beak excluded) were obovoid trigonous, with the length ranged from 1.53-3.59 mm. The nutlet length between different populations of the same species revealed stability and no significant difference exist by statistical analysis. (2)The epidermal cells were five to seven gonal, rarely four or eight, which was various within the different individuals of C. rouyana. The anticlinal wall was straight or microwave, and silica platform was flat, occasionally concave or slightly convex, with solitary central silica body but without satellite body. Whereas each epidermal cell of C. filipes var. kuzakaiensis and C. filipes var. tremula occasionally had two central silica bodies. (3)Based on the shape of epidermal cells, numbers of central silica platform, some species were distinguished from similar species, such as C. baimaensis and C. filipes, and it was also valuable to distinguish the varieties of C. filipes, ie. var. kuzakaiensis, var. oligostachys and var. tremula. (4)Sections Paniceae s.s. and Laxiflorae had a high consistency in the morphology and micromorphology of nutlets. It indicated that the morphology and micromorphology of nutlets were of great importance of taxonomic significance.

    Systematic and Evolutionary
    Chromosome Number and Karyotype Analysis of Different Populations in Sophora alopecuroides (Fabaceae)
    Xiayu HU, Yuping LIU, Xu SU, Ping YANG, Yanan WANG
    2023, 43(1):  9-19.  doi:10.7525/j.issn.1673-5102.2023.01.002
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    In order to explore the karyotype characteristics and evolutionary relationship of different populations of Sophora alopecuroides, the karyotype characteristics and evolutionary of six natural geographic populations distributed in Inner Mongolia, Gansu, Ningxia were analyzed respectively, and chromosome conventional slicing technology was used. The results showed that the number of chromosomes in six populations of S. alopecuroides was constant,2n=2x=36. There were two types of central centromere(m) chromosome and sub-central centromere(sm) chromosome in three populations. Chromosomes of most populations were only central centromere chromosome except for Population 3 in Wuwei, Gansu, with central centromere and sub-central centromere chromosome. The average arm ratio of chromosomes ranged from 1.19 to 1.37, the length ratio was between 1.72 and 2.19, and the karyotype asymmetry coefficient was from 54.30% to 57.17%. There were three types of karyotypes including 1A, 3A and 2B for S. alopecuroides. The karyotype asymmetry coefficient of population 3 of S. alopecuroides was the largest and the evolutionary degree was the highest, while those of population 19(Ordos, Inner Mongolia) was the smallest and the lowest. Cluster analysis showed that the six populations of S. alopecuroides were aggregated into two major branches of A and B. Branch A could be divided into two subclades of C and D. Among them, population 5(Wuwei, Gansu) and population 13(Alxa, Inner Mongolia) were clustered into subclade C, which had the closest relationship, whereas population 3 was clustered into subclade D alone, which was relatively distant with two populations from subclade C. Similarly, branch B could be further divided into subclade E and subclade F respectively. Subclade E was consisted of population 19 and population 43(Ordos, Inner Mongolia), which had the closer relationship, while Subclade F only contained population 17(Yinchuan, Ningxia), which had the relatively distant with two populations from subclade E. In this study, the chromosome number, karyotype characteristics and evolutionary trend of S. alopecuroides were discussed at the population level, which provided cytological evidence for further studying the system and evolution, and genetic diversity of germplasm resources of S. alopecuroides.

    Anatomical and Histochemical Features of the Pteris vittata (Pteridaceae)
    Teng LI, Cunyu ZHOU, Chaodong YANG, Zhanfeng LIU
    2023, 43(1):  20-29.  doi:10.7525/j.issn.1673-5102.2023.01.003
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    The perennial fern Pteris vittata(Pteridaceae) is a hyperaccumulator of arsenic and is used for remediation of soils contaminated by heavy metals. In order to identify the characters that the P.vittata sporophyte thrives in xeromorphic rocky environments and hyperaccumulates ions, the brightfield and epifluorescence microscopy were used to investigate the anatomical structures and histochemical features of this species. The results were as follows: (1)The structure of the rhizome, adventitious roots and leaves of P. vittata sporophytes were all primary structures, the adventitious roots had an vascular bundles, endodermis with Casparian band, lignified sclerenchyma layers, cortex, rhizodermis. (2)The rhizomes had a dictyostele, endodermis, cortex, epidermis, cuticle. (3)The stipes had a single vascular bundle with a central endodermis, cortex, sclerenchyma layers, while the epidermis had a cuticle. The pinnae had bifacial mesophyll with palisade tissue and spongy tissue, the epidermis had a cuticle. (4)The surfaces of the rhizodermis and the root hairs were pectin-rich and underlain by a lignified cortex, and permeability tests using a berberine tracer showed that these structures retained large volumes of berberine. In summary, the suberized endodermis, lignified sclerenchyma layers, bifacial mesophyll, and a cuticle, all of which reflect an adaption to xeromorphic rocky environments. The result of the berberine permeability test are consistent with the hyperaccumulation of ions by P. vittata.

    Genetic and Breeding
    Construction of Suppression Expression Vector and Genetic Transformation of BpSPL9 gene from Betula platyphylla
    Jinxia DU, Tingting SHEN, Haoran WANG, Yiping LIN, Huiyu LI, Lianfei ZHANG
    2023, 43(1):  30-35.  doi:10.7525/j.issn.1673-5102.2023.01.004
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    To clarify the function of SPL gene in growth and development of Betula platyphylla,the BpSPL9 gene was cloned, and the expression vector of BpSPL9 was constructed by CREST technology, and the genetic transformation was carried out by Agrobacterium mediated method, and the phenotype of the transgenic lines was observed, respectively. The results showed that the transgenic lines with BpSPL9 suppressed were successfully obtained. The height of transgenic lines was significantly lower than that of non-transgenic lines, with shorter node spacing and smaller leaf area. The contents of 6-BA and IAA in transgenic lines were lower than those of the non-transgenic lines. It is speculated that BpSPL9 gene participated in plant growth and development by affecting the synthesis of auxin and cell division.

    Proteomic Screening and RcBSK7 Resistance of Ricinus communis under Cadmium(Cd) Stress
    Huibo ZHAO, Zhiqiang ZHAO, Chunguang BAO, Qi WEN, Ruxin LI, Fenglan HUANG
    2023, 43(1):  36-50.  doi:10.7525/j.issn.1673-5102.2023.01.005
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    In order to reveal the mechanism of Ricinus communis response to heavy metal cadmium(Cd) stress, and screen out the resistance genes involved in Cd stress, by observing the seed germination and plant growth status, castor plants treated with water were used as controls to study their effects under three doses(300, 700 and 1 000 mg·L-1) of Cd stress. The response mechanism is expected to provide new ideas for revealing the defense and detoxification mechanism of castor plant under in Cd stress. Using differential proteomics to analyze the network regulation mechanism of castor under Cd stress, that is, with the increase of Cd stress concentration, the castor plant blocks the absorption of heavy metal Cd by roots, improves their own antioxidant capacity, and inhibits Cd2+ operation. As well as the induction of programmed cell death and other detoxification processes to resist Cd stress damage; according to the results of omics analysis, a significantly different gene RcBSK7 was screened. Through functional verification in Arabidopsis, it can be seen that this gene can improve tolerance of castor plants to Cd stress. This study enhances the understanding of the diversity and complexity of castor plants under three Cd stresses, and provides a valuable theoretical basis for the identification of Cd-tolerant genes and the restoration of heavy metal pollution in the soil.

    Genetic Diversity and Genetic Structure of the Rare and Endangered Plant Ferula fukanensis
    Lei YANG, Qiumei CAO, Ying FENG, Wenjun LI
    2023, 43(1):  51-58.  doi:10.7525/j.issn.1673-5102.2023.01.006
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    To clarify the genetic diversity and genetic structure of a rare and the endangered small population of Ferula fukanensis, it is the basis and prerequisite to develop effective conservation and management strategies. The genetic diversity and structure of 87 endangered plants F. fukanensis from three populations based on 10 pairs of SSR primers with good polymorphism and stable amplification were analyzed respectively. The results showed that small population of F. fukanensis had relatively high genetic diversity, the Nei’s gene diversity index(hS) among the populations was 0.514, the total Nei’s gene diversity index(hT) was 0.516, the observed heterozygosity(Ho) was 0.881, the expected heterozygosity(He) was 0.512, the Shannon information index(I) was 0.836 and the percentage of polymorphic bands(PPB) was 100%, and the genetic differentiation degree of F. fukanensis was very low(Fst=0.007), 95.9 % of the variation of F. fukanensis occurred within populations, and there was no significant correlation between genetic distance and geographical distance, 66.7% of the populations suffered from genetic bottlenecks. The results showed that F. fukanensis had abundant genetic variation and high evolutionary potential. Based on the current situation of this wild population, it is suggested to establish a protected area, and carry out in situ conservation and strengthen ex situ conservation measures such as introduction and artificial breeding to assist the conservation of F. fukanensis. This study can provide theoretical support for the conservation of plant resources of F. fukanensis and has important theoretical and practical significance.

    Screening and Phenotypic Identification of Seed Coat Pigmentation Mutants in Arabidopsis thaliana
    Na LI, Xiaonan WANG
    2023, 43(1):  59-68.  doi:10.7525/j.issn.1673-5102.2023.01.007
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    Flavonols play important roles in plant responses to various environmental stresses and in the regulation of seed coat development. In this study, a transparent seed coat mutant was obtained through ethyl methane sulfonate(EMS) mutagenesis screening, compared with wild-type Arabidopsis thaliana(Col-0), the mature seed color of the mutant was yellow, and its phenotypic trait was controlled by a recessive single gene. Using map-based cloning and fine-mapping technology, the mutant gene TT4(At5G13930) was mapped to BAC of MAH20 on chromosome 5, and the 1 299th base C of the TT4 was mutated to T, resulting in the 324th amino acid glycine mutated to glutamic acid. TT4(transparent testa 4) encoded a structural gene for flavonoid synthesis, chalcone synthase(CHS), and after mutation, the seed coat was transparent and the seed color was yellow, then the mutant was named tt4-1. The phenotype of brown seed coat was restored by functional complement mutants, which further demonstrated the important role of TT4 in regulating the development of seed coat color. The tissue expression analysis of TT4 was conducted by promoter coupling GUS assay, and it was found that TT4 gene was expressed in the roots, stems, leaves of plant seedlings and flowers respectively. Physiological phenotypic analysis showed that the mutant tt4-1 seeds germinated earlier, and the seedlings had shorter taproots, as well as more lateral roots and root hairs, larger stomatal opening and higher water loss rate in mature leaves compared with the wild type. This study would lay a theoretical basis for further elaborating the function of TT4 gene.

    Physiology and Ecology
    Effects of Tapping Panel Dryness on Mitochondrial Ultrastructure and ROS Metabolism in Barks of Rubber Tree (Hevea brasiliensis)
    Hong YANG, Lifeng WANG, Longjun DAI, Bingbing GUO
    2023, 43(1):  69-75.  doi:10.7525/j.issn.1673-5102.2023.01.008
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    In order to elucidate the mechanism of tapping panel dryness(TPD) and effectively control it, the ultrastructure and the expression patterns of reactive oxygen species(ROS)-related genes in barks from healthy(H) and different degrees of TPD trees were studied in this study. The results showed that with the development of TPD, aberrant mitochondrial ultrastructure changed including the loss of the matrix, swelling of cristae, and the cavitation of the inner cavity were observed in barks. The results of qRT-PCR experiments showed that the expression levels of HbPOD2 and HbPOD3 in TPD trees were higher than those in healthy trees, indicating the possibility of these genes being used as “marker” genes to monitor the tapping intensity, the stimulation intensity, and the occurrence of TPD. The gene HbCAT was also down-regulated in TPD trees, indicating that the balance between ROS generation and scavenging may be a key factor in the occurrence of TPD in rubber tree. The expressions of HbGST1HbGST2, and HbPPO in TPD trees were higher than those in healthy trees, indicating these genes may be associated with in-situ coagulation of latex during TPD occurrence. This study reveals the changes of ultrastructure and the expression patterns of ROS-related genes in rubber tree barks during TPD occurrence. These findings may provide a new perspective for elucidating the mechanism of TPD in rubber tree, and provid theoretical guidance for developing methods for monitoring tapping intensity and stimulation intensity and for developing TPD-related “marker” genes in rubber trees.

    Effects of Exogenous Hydrogen Sulfide on Contents of Organic Acids and Hormones in Leaves of Avena nuda under Saline-Alkali Stress
    Jianxin LIU, Ruirui LIU, Xiuli LIU, Xiaobin OU, Haiyan JIA, Ting BU, Na LI
    2023, 43(1):  76-89.  doi:10.7525/j.issn.1673-5102.2023.01.009
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    In order to explore the regulatory effect of exogenous hydrogen sulfide(H2S) on the levels of organic acids and hormones in plants under saline-alkali stress, naked oats(Avena nuda) were used as materials to study the effect of spraying 50 μmol·L-1 H2S donor sodium hydrosulfide(NaHS) solution on the contents of organic acids and hormones in leaves and yield traits under 3.00 g·kg-1 saline-alkali stress. The results showed that saline-alkali stress significantly increased the contents of succinic acid, butenedioic acid, malic acid, glucuronic acid and total organic acids, respectively, but significantly decreased the contents of pyroglutamic acid, jasmonoyl-isoleucine(JA-Ile), trans-zeatin(tZ) and N6-(Δ2-Isopentenyl) adenine(iP) in leaves respectively. Under saline-alkali stress, spraying NaHS solution significantly increased the contents of 3-Hydroxy-3-methylglutaric acid, indole-3-acetic acid(IAA), gibberellin A7(GA7), methyl jasmonate(MJA), iP and IAA/ABA ratio, respectively, but significantly decreased the contents of glucuronic acid, gibberellin A3(GA3), gibberellin A4(GA4), total gibberellins(GAs), 1-aminocyclopropanecarboxylic acid(ACC) and ACC/ABA ratio respectively, while it had no significant effect on the contents of succinic acid, butenedioic acid, malic acid, citric acid, malonic acid, pantothenic acid, nicotinic acid, pyroglutamic acid, suberic acid, phenylpyruvic acid, total organic acids, gibberellin A1(GA1), jasmonic acid(JA), JA-Ile, abscisic acid(ABA), tZ, trans-zeatin-riboside(tZR), N6-(Δ2-isopentenyl) adenosine(iPA), total jasmonic acids(JAs), cytokinin(CTK) and the ratios of GAs/ABA, JAs/ABA and CTK/ABA respectively. The principal component analysis showed that spraying NaHS solution significantly increased the contents of organic acid 3-hydroxy-3-methylglutaric acid and hormones MJA, GA7, tZ and IAA in leaves of naked oat under saline-alkali stress by 14.31%, 41.83%, 50.00%, 22.97% and 13.02%, respectively; while the contents of organic acids nicotinic acid, glucuronic acid and hormones GA4, ACC, tZR and GA3 were significantly decreased by 16.00%, 23.87%, 73.53%, 32.72%, 50.00% and 33.91%, respectively. In addition, the application of NaHS solution reduced the 1 000 grain weight of naked oat under saline-alkali stress by 5.91%, while spike number, boll number per spike, spike grain numbers and grain yield were increased by 2.19%, 9.70%, 61.60% and 52.83%, respectively. These results indicated that exogenous H2S participates in the regulation of organic acid and hormone levels of naked oat under salt-alkali stress, which could enhance the ability of naked oat to adapt to salt-alkali stress.

    Photosynthetic Capacity Differentiation and Gene Transcription in Different Geographical Populations of Arabidopsis thaliana under Common Garden conditions
    Mengshuo LI, Yingze LIU, Huan LU, Sheng QIANG
    2023, 43(1):  90-99.  doi:10.7525/j.issn.1673-5102.2023.01.010
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    Photosynthesis is a basic metabolism process for plants and provides the material basis for plant growth and development. Different environmental conditions determine the polymorphism of plant photosynthetic capacity, but the mechanisms regulating the divergence of photosynthetic capacity among different populations under the same environmental conditions remain still unknown. This study aims to reveal the divergence of photosynthetic capacity in different geographical populations of Arabidopsis thaliana in Europe under common garden conditions and the mechanisms of their gene transcriptional regulation. A comparative study of photosynthetic characteristics of 23 geographic A. thaliana(Arabidopsis) populations from different regions was conducted under common garden conditions by determining the gas exchange parameters, chlorophyll fluorescence parameters and SPAD values. In addition, the photosynthetic-related gene expressions of the typical populations with differences in photosynthetic capacity was examined using real-time quantitative PCR(RT-qPCR). The comparative result revealed that gas exchange parameters differed significantly among geographical populations of Arabidopsis from different climatic zones in Europe. The variation range of net photosynthetic rate was 2-11 μmol·m-2·s-1.while chlorophyll fluorescence parameters varied to a lesser extent, the variation range was almost no more than 10%. Cluster analysis showed that the 23 Arabidopsis populations were divided into two groups, strong and weak photosynthetic ability respectively. The populations with strong photosynthetic capacity were mainly distributed in central and western Europe, and the average net photosynthetic rate was 7.37 μmol·m-2·s-1. The populations with weak photosynthetic capacity were mainly distributed in eastern and southern Europe with an average net photosynthetic rate of 4.46 μmol·m-2·s-1. Correlation analysis revealed a significant correlation between net photosynthetic rate, water use efficiency and SPAD. The results of redundancy analysis(RDA) suggested that the divergence of photosynthetic capacity in Arabidopsis might be related to environmental factors such as temperature and rainfall during the growing season in the region. RT-qPCR results showed that the expression of PSⅡ- and Rubisco-related genes were significantly higher in En-D and Stw-0, typical populations with strong photosynthetic capacity, than in Wa-1 and Per-1, typical populations with weak photosynthetic capacity, suggesting that transcriptional differences in PSⅡ and Rubisco genes could be involved in the regulation of photosynthetic capacity differentiation in populations. The results clarified that there were differences in photosynthetic capacity between geographic populations of Arabidopsis under common gardens, and such differences might be related to the environment of origin and have been inherited to future generations during long-term evolution. In contrast, the transcriptional regulation of PSⅡ and Rubisco-related genes might be involved in the differentiation of photosynthetic capacity in Arabidopsis.

    Spatial Variation of Phenotypes of Fruit and Seed Traits of Michelia wilsonii, a Rare and Endangered Plant
    Lijie CHEN, Wanyuan DANG, Weiwei CHEN, Tao QIU, Xiaohong CHEN
    2023, 43(1):  100-108.  doi:10.7525/j.issn.1673-5102.2023.01.011
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    In order to provide a basis for the conservation and utilization of Michelia wilsonii natural population, the phenotypes of fruit and seed traits of M. wilsonii were analyzed, and the variation mechanism and spatial autocorrelation was studied. M. wilsonii natural population was taken as materials, which located in Zhougong Mountain, Ya’an, 12 phenotypic traits were determined. The spatial variation characteristics of fruits and seeds of M. wilsonii were explored by using coefficient of variation and semi-variogram. The results showed that:(1)The average coefficient of variation of phenotypic fruit and seed traits was 27.59%, the variation extent of morphological traits was the least, and the variation extent of seed traits was more abundant than that of fruit. (2)The seed abortion rate and follicle abortion rate were the highest in the lower part of fruit, which were 18.32% and 38.22% respectively. The seed and follicle abortion rates were lowest in the middle part of fruit, which were 15.05% and 23.45% respectively. (3)The semi-variogram models were dominated by exponential and spherical models, presenting a distribution of aggregation. Except fruit length, seed longitudinal diameter and seed abortion rate, the other nine indexes showed medium and high spatial autocorrelation respectively. (4)The anisotropy ratios of the nine indexes were close to 1, and the spatial heterogeneity was isotropy. Therefore, the phenotypic fruit and seed traits of M. wilsonii had abundant variation in the medium scale spatial range.

    Molecular biology
    Analysis of the Chloroplast Genome Characteristics of 6 Species of Yucca
    Fei WANG, Wenzhi ZHAO, Zhanghong DONG, Luyao MA, Weiying LI, Zongyan LI, Peiyao XIN
    2023, 43(1):  109-119.  doi:10.7525/j.issn.1673-5102.2023.01.012
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    In order to clarify the characteristics and sequences variation of the chloroplast genomeof Yucca, a comparative genomics of the chloroplasts was performed, and a phylogenetic tree based on the chloroplast genome was constructed. The chloroplast genome of Y. treculeana was obtained by high-throughput sequencing technology, and combined with the published chloroplast genome of Yucca, the chloroplast genomes of six species of Yucca were studied by comparative genomics, including basic structure, SSR, boundary contraction and expansion, sequence variation and phylogenetic analysis respectively. The results showed that the chloroplast genome size, gene type and number of the six Yucca species were similar, and the interspecific genome structure was conserved. Several repeated sequences were detected in the chloroplast genome of Yucca, among which SSR loci were mostly composed of mononucleotide, dinucleotide and tetranucleotide, and preferred A and T bases. Three regions with high variation(psbK-psbl-trnS-GCUrpl20-rps12 and ccsA-ndhD) were identified from the chloroplast genomes of six Yucca species according to the nucleic acid polymorphism index(π)≥0.008. The phylogenetic relationships constructed from the chloroplast genome and LSC+SSC region sequences were basically consistent, and the phylogenetic relationships among six Yucca species were confirmed, among which Y. treculeana and Y. queretaroensis were most closely related. The sequencing obtained Y. treculeana chloroplast genome, revealed the genome characteristics and sequence variation of six Yucca species, and clarified the relatedness among various species. The results could provide reference for subsequent molecular marker development and phylogenetic research.

    Complete Chloroplast Genome Structure and Characterization of Syringa villosa subsp. wolfii
    Yongchang LU, Xin ZHANG, Luyan ZHANG, Jiuli WANG
    2023, 43(1):  120-130.  doi:10.7525/j.issn.1673-5102.2023.01.013
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    To clarify the basic characteristics of the complete chloroplast genome of Syringa villosa subsp. wolfii, the sequence information of chloroplast genome was analyzed by high-throughput sequencing technology, and its systematic evolution position was discussed. The results showed that:(1)The total length of the S. villosa subsp. wolfii chloroplast genome was 156 517 bp, which had a typical tetrad structure and had 131 functional genes, including 36 tRNA genes, 8 rRNA genes and 87 protein-coding genes respectively. (2)The relative synonymous codon usage(RSCU) analysis of the protein-coding region of the chloroplast genome showed that there were 31 codons with RSCU>1, of which 21 ended with A/U base; and there were 34 codons with RSCU<1, including 22 codons ending with G/C base. (3)In the chloroplast genome of S. villosa subsp. wolfii, 334 scattered repeats were detected, including 170 forward repeats and 164 palindromic repeats, and 227 SSR loci were discovered, and PCR primers were designed successfully for 226 of these loci. (4)Phylogenetic tree analysis based on the maximum likelihood method showed that S. villosa subsp. wolfii was the most closely to the S. yunnanensis. In this study, repeated sequences, IR boundaries and phylogeny of chloroplast genome of S. villosa subsp. wolfii were analyzed to provide reference data for molecular markers, phylogenetic classification, species identification and evaluation and DNA barcode development.

    Cloning and Expression Analysis of MibZIP1 from Macadamia integrifolia
    Haiyun SONG, Tao ZHANG, Peng HE, Shufang ZHENG, Lifeng WANG, Wenlin WANG
    2023, 43(1):  131-139.  doi:10.7525/j.issn.1673-5102.2023.01.014
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    In order to clarify the potential functions of bZIP transcription factor family members in Macadamia integrifolia under stress response, MibZIP1 was cloned from ‘Guire 1’ fruit. Combined with the analysis of transcription factor structure and expression patterns under different treatments, it was found that the full length of MibZIP1 was 1 157 bp, and the ORF was 927 bp, and encoded 308 aa,and had a typical bZIP Superfamily domain. Phylogenetic analysis showed that MibZIP1, TsbZIP60 and NnbZIP60 were closely related. The results of tissue expression analysis showed that MibZIP1 expression was the lowest in leaves of ‘Guire 1’ and the highest in branches of ‘695’. The expression of MibZIP1 was significantly up-regulated in ‘Guire 1’ leaves treated by zeatin, salicylic acid, ethephon and abscisic acid respectively, but was unchanged treated by gibberellin and hydrogen peroxide respectively. It was speculated that MibZIP1 was related to the stress tolerance of M. integrifolia, which provided theoretical guidance for the development of new cultivation and hormone regulation techniques.

    Plant synecology
    Competition Pattern of Standing Trees in Secondary Pinus Forest in the Ziwuling Mountains, China
    Shuzhen ZOU, Caijia YIN, Qian YANG, Long MA, Di KANG
    2023, 43(1):  140-149.  doi:10.7525/j.issn.1673-5102.2023.01.015
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    In order to reveal the driving mechanism of competition dynamics and pattern formation in the process of arid forest restoration and succession, the competition and spatial distribution pattern of standing trees in arid forest China were studied, and a typical secondary Pinus tabuliformis forests was investigated in the Ziwuling Mountains, China, and four larger sample sites(0.25 hm2 each) in different developmental stages were selected, according to the method using space instead of time, and some details of population, size, inter-tree competitions and spatial pattern of four sample sites were acquired respectively. The results showed that, in the four communities at different stages of succession, population densities of P. tabulaeformis were 1 476, 996, 800 and 648 per ha2 respectively; population densities of Betula platyphylla were 48, 32, 44 and 16 per ha2 respectively; and population densities of Populus davidiana were 64, 28, 24 and 12 per ha2 respectively. Competition index of main tree specials decreased with succession, and showed P. tabulaeformis>B. platyphylla>P. davidiana. Quantity of small individuals(diameter at breast height from 2-15 cm) decreased obviously; but quantity of large individuals(diameter at breast height larger than 30 cm) increased. In all succession stages, the competitive intensity of P. tabulaeformis decreased with the increase of diameter. The horizontal spatial competition pattern of P. tabulaeformis showed a patchiness distribution. P. tabulaeformis clumped at the scales 0-5 m, and negative correlated with other tress specials at the scales 5-15 m. Quantity of small size Pinus individuals decreased obvious in later developmental stage. Inter-tree competition of P. tabulaeformis was stronger than other tree species, and inter-tree competition decreased in the later developmental stage. The conclusions are as follows: the size of trees are negatively correlated with the competition index; the competition index of P. tabulaeformis is higher than other species; the competition at community scales decline as development, and the quantity and range of the patches with an intense competition decline, but do not disappear yet. Competition and spatial relations are observed within the scales of 5-15 m which are larger than the average crown size of Pinus. The conditions suggest that the range of inter-tree influence could expand indirectly beyond their crown range through unknown methods, which should be further investigated.

    Plant reproductive biology
    Reproductive Biological Characteristics of Dendrobium chrysanthum
    Jianwei YANG, Zongyan LI, Yao FENG, Shuxian REN, Menglu HU, Songpu YE
    2023, 43(1):  150-160.  doi:10.7525/j.issn.1673-5102.2023.01.016
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    In order to clarify the reproductive biological characteristics of Dendrobium chrysanthum, the flowering habits, the pollen vitality, the characteristics of stigma secretion, the fruit setting rate as well as the development and storage of seed were investigated. The results were listed as followed: (1)Its budding period and the emergence were 19 d, 23 d respectively. The population's flowering period was 28d, whereas the single flower span was from 10-15 d. (2)From the first day to the third day of flowering, the pollen viability was about 90% but decreased to 23.7% at the ninth day of flowering. The data of pollen viability significantly differed between at three former day and other latter time(P<0.01), pollen viability varied from high to low level with the blooming. (3)The stigma of D. chrysanthum produced secretions from the 2nd day of flowering, and had the maximum yield at the 6th day, and stigma staining showed that the stigma receptivity was optimal at the 5-6 d of flowering, and stigma receptivity changed from weak to strong to and then to weak with the prolongation of bloom stage. (4)An artificial pollination was made at the fourth day after flowering. but no fruit was found after cross-pollination and same-flower pollination. In the field, the seedpod weight was from 2.02-4.83 g, seed length varied from 0.628-0.845 mm and its width was from 0.082-0.110 mm, and the ratio of length to width was 7.798 and the rate of embryo formation reached to 97.35%, and the seed vigor was 90.80%, and the seed vigor maintained at 73.20% at room temperature for 6 months. All results mentioned above indicated that the flowering period of D. chrysanthum was short, and the pollen vigor remained the highest after flowering, and the pollen matured earlier than stigma. There was no apomixis occurred in D. chrysanthum, and the artifical self-pollination caused sterile. Although it could bear well-developed seedpods under natural condition with a high seed vitality. Dried seeds could keep a good storage resistance under natural condition. This study confirms the biological characteristics of flowering and dichogamy of D. chrysanthum, and its breeding system belongs to self-incompatibility, and could provide the strategies for conservation of wild germplasm resources and a precise hand-pollination of D. chrysanthum.