14 August 2024, Volume 44 Issue 1

    

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Original Article
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  Intraspecific genetic variation within chloroplast genome of a rare and endangered species Paphiopedilum parishii (Orchidaceae)

  GAO Xinzhen^1,2, TANG Lu¹, WANG Yu^1,3, SHAO Shicheng¹, LUO Yan^1*

  Guihaia. 2024, 44(1): 14-15. https://doi.org/10.11931/guihaia.gxzw202211070

  Abstract ( 53)   Knowledge map   Save

  Paphiopedilum parishii is a rare and endangered species with few localities and fragmented populations found in China, Myanmar, Thailand and Laos. Environmental changes and over-harvesting have led to a decrease in its wild populations. It is important to protect endangered species' genetic diversity since it provides the species with the ability to adapt and survive. However, little is known about the genetic information of this species. This study aims to detect intraspecific variation and develop polymorphic genetic markers of P. parishii. The complete chloroplast genome of four individuals of wild P. parishii was obtained by sequencing, assembling and annotating, then compared with the existing genomic data of two individuals available from GenBank to detect the intraspecific variation. Further, simple sequence repeats(SSRs), single nucleotide polymorphisms(SNPs), and insertions and deletions(InDels)were identified. The results were as follows:(1)The four new sequencing chloroplast genomes were quadripartite, with a length between 154 403 bp and 154 809 bp, with 129 genes(78 protein coding genes, 39 tRNAs, 8 rRNAs and four pseudogenes).(2)As a result of comparison of six individuals, 103-107 SSR loci were identified in the chloroplast genome of six individuals of P. parishii, and 21 SSRs were polymorphic. And 60 long repeats were found, including 17-21 forward repeats, 18-29 reverse repeats, 9-16 palindromic repeats, and 4-9 complement repeats.(3)In addition, a total of 10 SNPs and 60 InDels were uncovered across the plastome. Three of the non-synonymous mutations caused amino acid changes in functional domains. 19 InDels might be selected for possible chloroplast DNA markers to determine intraspecific variation.(4)The value of nucleotide diversity(P_i)was calculated ranging from 0-0.006 32 suggesting sequences with low variation. Hyper-polymorphic regions, e.g. intergenic spacers rps3-rpl22, trnL-UAC-rpl32, rpoB-trnC-GCA and ycf4 gene were identified as potential barcoding regions.(5)The phylogenetic analyses based on the complete chloroplast genome supported three lineages in Paphiopedilum, and six individuals of P. parishii form a monophyletic group. SSRs, long repeats, InDels, SNPs and nucleotide sequences showed sufficient intraspecific genetic variation in P. parishii. The molecular markers developed here will contribute to further evolutionary studies and conservation of P. parishii.
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  Characteristics of chloroplast genome and phylogenetic analysis of Diospyros sutchuensis with extremely small populations

  YANG Nan¹ , WANG Ao¹ , ZHANG Zichen¹ , ZHAO Liangcheng^2*

  Guihaia. 2024, 44(1): 29-29. https://doi.org/10.11931/guihaia.gxzw202306039

  Abstract ( 60)   Knowledge map   Save

  Diospyros sutchuensis is a national protected wild plant species with narrow distribution and extremely small population in southwestern China. At present, the genomic information of this species is lacking and its phylogenetic relationships among Diospyros remain unclear. In this study, the chloroplast genome of D. sutchuensis was sequenced by Illumina platform, assembled and annotated by Getorganelle v1.7.3.4 and PGA, and analyzed by DnaSP 6.12.03 for sequence comparison, REPuter, Tandem Reapeats Finder, MISA for repetitive sequences, CodonW1.4 for codon usage bias, and EasyCodemL for selection pressure. Meanwhile, based on four different chloroplast genome sequence datasets, the phylogenetic relationships between D. sutchuensis and 11 Diospyros species were analyzed using IQtree. The results were as follows:(1)The chloroplast genome of D. sutchuensis was 157 917 bp in length, including two inverted repeats(IRs)of 26 111 bp, which was separated by large single copy(LSC)and short single copy(SSC)of 87 303 bp and 18 392 bp, respectively. The GC content was 37.4%.(2)The genome contained 113 genes, including 79 protein-coding genes, 30 tRNA genes, and 4 rRNA genes. A total of 49 long repeats, 27 tandem repeats, and 34 simple sequence repeats were identified. There were 31 high-frequency codons in protein-coding genes, most of them ended in A or U, and the most used codons were the ones encoding leucine. The coding regions were more conserved than the non-coding ones, and 10 regions were identified as most divergent hotspots for potential molecular markers. There had been positive selection on ndhB, ndhG, ndhI, rbcL, rpoB, petB, petD and rps12 among protein-coding genes.(3)Phylogenetic analyses showed that D. sutchuensis was closely related to D. rhombifolia and D. cathayensis. Together with D. hainanensis, these four species formed a monophyletic group. The phylogenetic tree constructed from the chloroplast genomes had the highest support values, indicating that the chloroplast genomes with most variable and informative sites are more suitable for phylogenetic studies of Diospyros. The results provide useful chloroplast genomic resources for germplasm identification, genetic diversity conservation, repopulation, and phylogenetic analysis of D. sutchuensis as well as Diospyros.
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  Analysis of chloroplast genome features of endangered and rare plant Camellia minima

  DENG Yongbiao, ZHANG Jin, LAN Lunli, ZHAO Bo^*

  Guihaia. 2024, 44(1): 30-42. https://doi.org/10.11931/guihaia.gxzw202304069

  Abstract ( 44)   Knowledge map   Save

  Camellia minima, a rare and endangered species of sect. Chrysantha, has not been previously explored in terms of its chloroplast genome. Utilizing the Illumina HiSeq 2000 platform, the chloroplast genome sequence of C. minima was sequenced, assembled, annotated, and analysed. The results were as follows:(1)The chloroplast genome of C. minima was 156 961 bp in length, embodied a typical tetrad structure, and contained 136 annotated genes, including 87 protein-coding genes, 41 tRNA genes, and 8 rRNA genes.(2)The analysis identified 66 SSR loci and 39 repetitive sequences.(3)Codons prefered to use codons ending in A/U. Comprehensive effective number of codons(ENC)mapping, PR2-plot, and neutral analyses suggested natural selection as a primary factor shaping codon usage patterns.(4)Boundary analysis showed variation in the length and position of the ycf1 gene among different species of yellow Camellia.(5)Phylogenetic analysis of the chloroplast genomes of published sect. Chrysantha species revealed that C. minima was most closely related to C. micrantha. This study provides crucial references for exploring species evolution and enhancing exogenous gene expression, establishing a theoretical foundation for the conservation and utilization of species of sect. Chrysantha in the future.
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  Comparative analysis of chloroplast genomes of two rare Pecteilis species(Orchidaceae)

  WANG Yu^1,2, TANG Lu¹, SHAO Shicheng¹, MA Changle^2,3, LI Jian⁴, LUO Yan^1*

  Guihaia. 2024, 44(1): 43-55. https://doi.org/10.11931/guihaia.gxzw202304063

  Abstract ( 63)   Knowledge map   Save

  Pecteilis susannae and P. hawkesiana are rare and endangered species with important medicine and ornament value. However, little is known about the genetic information of these two species. In order to understand the basic characteristics of the chloroplast genome of these two Pecteilis species, and to develop molecular markers for species identification, conservation genetic and phylogenetic analysis, the genome skimming approach using next-generation sequencing methods was used to generate chloroplast DNA sequences in this study. The chloroplast genomes were assembled and annotated by bioinformatics analysis. Simple sequence repeats(SSRs), single nucleotide polymorphisms(SNPs), and insertions and deletions(InDels)were identified. Furthermore, comparative chloroplast genomic and phylogenetic analyses were conducted with closely related species. The results were as follows:(1)The newly sequenced chloroplast genomes of P. susannae and P. hawkesiana were 154 407 bp and 153 891 bp in size. They comprised a pair of 26 550 bp and 26 523 bp inverted repeats(IR)that separated a large 84 204 bp and 83 756 bp single copy region(LSC)and a small 17 103 bp and 17 089 bp single copy region(SSC), respectively. Both chloroplast genomes contained 111 unique genes, including 77 protein-coding genes, 30 tRNA and 4 rRNA genes.(2)Ninety-four simple sequence repeats(SSRs)were identified in the P. susannae chloroplast genome and 92 in that of P. hawkesiana.(3)Comparisons of two chloroplast genomes revealed that there were nucleotide variations including 706 single-nucleotide polymorphism sites and 152 InDels between the two Pecteilis species, of which several markers(cpInDel 067)could discriminate the two Pecteilis species.(4)The one most divergent gene(accD)and the nine most divergent intergenic regions(rps19-psbA, matK-trnQ-UUG, psbM-psbD, trnT-UGU-ndhJ, accD-psaI, ycf4-cemA, clpP-psbB, ndhF-trnL-UAG, rps15-ycf1)among genomes were detected.(5)The phylogenetic analysis based on the chloroplast genome sequences revealed that P. susannae, P. hawkesiana and Habenaria dentata are closely related. The molecular markers(SSRs, InDels and hotspots)developed from the chloroplast genomes of two Pecteilis species in the present study can be used to identify related species and provide valuable genetic resources in utilizing and conserving natural resources.
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  Flower bud differentiation and leaf endogenous hormone changes of Camellia perpetua

  JIANG Haidu^1,2, SUN Feifei¹, QIN Huizhen¹, TANG Jianmin¹, WEI Xiao^1,2, CHAI Shengfeng^1,2*

  Guihaia. 2024, 44(1): 56-67. https://doi.org/10.11931/guihaia.gxzw202212039

  Abstract ( 75)   Knowledge map   Save

  Camellia perpetua is the only rare and endangered plant in the genus Camellia that blooms almost all year round. In order to explore the flower bud differentiation process and the changes of endogenous hormones in leaves at different flower development periods and annual growth cycles, the process of C. perpetua flower bud differentiation was observed by paraffin sections. The contents of abscisic acid(ABA), indole-3-acetic acid(IAA), gibberellin(GA₃)and zeatin nucleoside(ZR)in leaves in different flower development periods and in leaves with flower bud and leaves without flower bud in annual growth cycle were determined by enzyme-linked immunosorbent assay(ELISA). The results were as follows:(1)The flower bud differentiation sequence of C. perpetua was from the outside to the inside, and it was divided into six periods, which lasted 35 d in total, from the bud differentiation to flowering about two months.(2)The contents of ABA and GA₃ and the ratios of GA₃/ABA and(IAA + GA₃)/ZR were higher in flower bud morphological differentiation period, while the contents of IAA and ZR and the ratios of IAA/ABA and ZR/ABA were lower.(3)The contents of ABA, IAA and ZR in the leaves with flower bud were higher than those in the leaves without flower bud. The IAA/ZR and(IAA + GA₃)/ZR ratios were lower than those of the leaves without flower bud. In conclusion, the flower bud differentiation to flowering time of C. perpetua is shorter. High levels of ABA and GA₃ and low levels of IAA and ZR are beneficial to flower bud differentiation; higher levels of ABA, IAA and ZR are beneficial to flower bud development. The study provides the reference for clarifying the continuous flowering mechanism of this species.
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  Effects of simulated drought by PEG-6000 on the germination of Hopea chinensis seeds under different temperature conditions

  LIANG Huizi¹, YANG Jisheng¹, QIN Yi², PAN Weihu², XIAO Yufei¹, HUANG Ronglin¹, WANG Renjie¹, JIANG Yi¹, LIU Xiongsheng^1*

  Guihaia. 2024, 44(1): 68-76. https://doi.org/10.11931/guihaia.gxzw202301019

  Abstract ( 41)   Knowledge map   Save

  Hopea chinensis is distributed in China and its seeds are typically reclacitrant. In order to investigate the germination adaptability of seeds to temperature and moisture, we carried out an experiment with three different constant temperatures(15, 20, 25 ℃)controlled by artificial climate incubators, and used six polyethylene glycol(PEG-6000)concentrations(0%, 5%, 10%, 15%, 25% and 35%)to simulate drought stress. The germination characteristics of these seeds were carefully examined. The results were as follows:(1)Temperature exerted a significant influence on seed germination. Regardless of the level of drought stress applied, higher temperatures positively affected the germination percentage, germination energy, germination index, radicle length, sprout length and vitality index of seeds, higher temperatures led to shorter germination delay and increased fluctuations in the germination duration.(2)Drought stress had a significant impact on seed germination. Under identical temperature conditions, increasing levels of drought stress resulted in decreasing of germination percentage, germination energy, germination index, germination duration, radicle length, sprout length and vitality index of seeds. Moreover, higher levels of drought stress led to longer germination delay of seeds.(3)The interaction between temperature and drought stress had a significant influence on seed germination. Under drought stress, seed germination exhibited different responses under different temperature conditions. Specifically, under conditions where a PEG-6000 concentration of 35% was applied as drought stress treatment, the germination percentage at temperatures of 20 ℃ and 25 ℃ were significantly higher than those observed at 15 ℃(8.89% and 15.55% compared to lower percentage at 15 ℃). However, it was important to note that when subjected to both 35% PEG-6000 and a temperature of 15 ℃, the seeds no longer germinate. In summary, our results indicate that the suitable temperatures for seed germination are identified as being at 20 ℃ and 25 ℃. It is determined that the most favorable temperature for early seedling growth is 25 ℃. As the drought stress intensifies, the inhibitory effect on seed germination become stronger, the effect of drought stress on seed germination is higher than that of temperature. Additionally, moderate warming can help alleviate the inhibitory effect of drought stress on seed germination.
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  Floral morphology and embryological features of anther development in Renanthera imschootiana

  WANG Yuecheng¹, TAO Kaifeng¹, ZHU Yong¹, ZHANG Jin¹, LUO Yan², LI Lu^1*

  Guihaia. 2024, 44(1): 77-88. https://doi.org/10.11931/guihaia.gxzw202211009

  Abstract ( 43)   Knowledge map   Save

  There are few data on the rare and endangered orchids of Renanthera Lour. Floral morphology and embryological features of anther development in R. imschootiana were investigated, and the taxonomic significance of R. imschootiana was analyzed by comparing with existing data. The results were as follows:(1)Flowers were characterized by such taxonomic features as tri-lobed labium with an unconspicous spur, cylindrical column, purple anther cap with yellow stripes, and a pair of deeply cleft pollinia connected by a well-developed stipe and a viscidium.(2)Anther primordium was differentiated into two lateral thecae containing two densely dyed microsporangia, and then, a sterile septum was formed longitudinally and unequally which divided each microsporangium into two jointly sub-microsporangium. The septum became absorbed during microsporogenesis and collapsed when anther ripened, resulting in a pair of deeply cleft pollinia.(3)The developed anther wall comprised 5-6 layers, including an epidermis, 2-3 endothecium, a middle layer, and a tapetum, which conformed to the massive type. Tapetal cell was uni-nucleated and glandular.(4)Microspore mother cells underwent a simultaneous cytokinesis during meiosis resulting in the tetrahedral or isobilateral microspore tetrads. Finally, each microspore retained in tetrads and produced 2-celled pollen via mitosis. Pollen tetrads were compactly arranged, leading to a hard cleft pollinia in each thecae. No pollen abortion was observed during anther development. The results provide new reference for taxonomy and conservation of Renanthera.
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  Floral structure and gynostemium ultrastructure of two Habenaria species with their taxonomic implications

  TAO Kaifeng, ZHU Yong, WANG Yuecheng, ZHANG Yingduo, LI Lu^*

  Guihaia. 2024, 44(1): 89-101. https://doi.org/10.11931/guihaia.gxzw202211038

  Abstract ( 44)   Knowledge map   Save

  The genus Habenaria exhibits a highly diversity in floral morphology and has complex taxonomy problems. In order to select key taxonomic features of this genus, floral structure and gynostemium ultrastructure of H. dentata and H. glaucifolia were investigated using the stereo microscope and scanning electronic microscope(SEM). The results were as follows:(1)There were significant differences in floral features between species, especially in the presence or the absence of lateral lobes of petal, morphology of 3-lobed lip, and the length ratio of the spur to the ovary.(2)The ultrastructures of gynostemium were obviously different between the two species, which were shown in shapes of staminode, outer epidermal cells of anther wall, and stigma branch.(3)Exine sculptures of massula were distinguished in two species, the reticulate type in H. dentata, and the baculate → reticulate type in H. glaucifolia. It was suggested that some floral features were selected as potentially valuable for species delimitation, including the presence or absence of lateral petal lobes, variations in spur morphology, the length ratio of the spur to the ovary, and the types of pollen exine sculpture. Additional data on floral features and ultrastructures of gynostemium were reported as supplement for understanding of H. glaucifolia. Notably, it was not confirmed that H. glaucifolia should be treated as an independent genus from Habenaria.
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  Floral morphology and anther development in diandrous orchid Paphiopedilum purpuratum with their taxonomic implications

  ZHU Yong¹, HUANG Jialin², TAO Kaifeng¹, WANG Yuecheng¹, ZHANG Jin¹, LI Lu^1*

  Guihaia. 2024, 44(1): 102-112. https://doi.org/10.11931/guihaia.gxzw202304052

  Abstract ( 47)   Knowledge map   Save

  The taxonomy of Paphiopedilum Pfitz. has been disputed and needs more data for clarification. Floral morphology and anther development in P. purpuratum were observed using microscope and paraffin section. The results were as follows:(1)It was supported that P. purpuratum should be placed in Paphiopedilum subgenus Paphiopedilum sect. Barbata by some floral features, including a single flower, sepal white with veins, petal spotted with blackish-maroon, pouch of a lip auriculate on both sides, and a staminode lunate.(2)At the early stage, anther primordium developed into a pair of laterally juxtaposed thecae. An incomplete sterile septa was differentiated in the center of each theca, giving rise to two arc-shaped microsporangia. When anther split, the sterile septum was discomposed and degenerated resulting in a mass of sticky pollens from two pollen sacs were fused into a unit.(3)The developed anther wall consisted of an epidermis, an endothecium, a middle layer, and a tapetum, conforming to the monocotyledonous type. Both tapetum and the inner tapetum cells contained 2 nuclei. At the stage of 2-celled grains, degeneration occurred in the epidermis and tapetum layers, while the endothecium became thickened fibrously.(4)Microspore mother cells underwent a simultaneous cytokinesis resulting in microspore tetrads with varied arrangements of tetrahedral, isobilateral, and decussate types, and the meiotic activity of microspore mother cells in the same theca was obviously asynchronous and different meiosis phases could be observed.(5)Microspores produced 2-celled pollens via a mitosis, which could be retained in pollen tetrads or released as monad. Based on the data available, some key features are selected for taxonomy and conservation biology of Paphiopedilum in Cypripedioideae, including the differentiation of incomplete sterile septum, the monocotyledonous type of anther wall, the binucleated tapetum, differentiation of the inner tapetum, simultaneous cytokinesis, the sticky pollens, and so on. This study provides new information for taxonomy and conservation biology of Paphiopedilum, as well as of Cypripedioideae.
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  Comparative study on leaf anatomical structures and photosynthetic characteristics of three Geodorum species

  XU Aizhu^1,2, JIANG Haidu², PU Qiankun³, WEI Xiao², WEI Yujing², LUO Yajin⁴, CHAI Shengfeng^2*

  Guihaia. 2024, 44(1): 113-125. https://doi.org/10.11931/guihaia.gxzw202302011

  Abstract ( 68)   Knowledge map   Save

  To explore leaf anatomical structures and photosynthetic characteristics of Geodorum plant, the anatomical structure of leaves, daily variation of photosynthesis, light response curve, CO₂ response curve, chlorophyll content and other indexes of the narrowly endangered Geodorum eulophioides and widely spread G. densiflorum and G. attenuatum were measured. The results were as follows:(1)Three species of Geodorum did not have spongy and fenestrated tissue differentiation in their chloroplasts, and stomata were distributed only in the lower epidermis. Compared with G. densiflorum and G. eulophioides, G. attenuatum had a greater leaf thickness and smaller stomatal density, exhibiting structural characteristics that were more adaptable to low light environments.(2)The daily changes of net photosynthetic rate(P_n)of three species of Geodorum showed a “bimodal” curve, and the photosynthetic “lunch break” was mainly caused by non-stomatal limitation. The daily mean values of P_n and water use efficiency(WUE)showed that G. attenuatum > G. densiflorum > G. eulophioides, which indicated that G. eulophioides had a weaker ability of accumulating photosynthesis products, and its adaptive capacity to the arid environment was probably poorer.(3)Three species of Geodorum were all shade plants. G. densiflorum had the smallest light compensation point(LCP)and the largest light saturation point(LSP), and had a wider range of adaptation to light intensity; G. attenuatum had a high maximum net photosynthetic rate(P_max)and apparent quantum efficiency(AQY), and its photosynthetic capacity was stronger; G. eulophioides had the smallest P_max and the potential maximum net photosynthetic rate(A_max), and its photosynthetic capacity and CO₂ utilization capacity were weaker.(4)The chlorophyll a(Chl a), chlorophyll b(Chl b)and total chlorophyll(Chl)contents of G. densiflorum and G. attenuatum were significantly(P<0.05)higher than those of G. eulophioide.(5)There were significant(P<0.05)correlations between the leaf thickness, mesophyll thickness, chlorophyll content, and P_max of three species of Geodorum. It was concluded that the photosynthetic capacity and adaptability of G. eulophioides were poorer compared with G. densiflorum and G. attenuatum, which might be greatly related to its endangerment; appropriate shading and increased CO₂ concentration favored photosynthesis in three species of Geodorum. The results of this study provide a reference for the analysis of the endangered causes of G. eulophioides and the conservation of germplasm resources of three Geodorum species.
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  Cytomorphology, physiological and biochemical characteristics of male sterility plant in Parakmeria omeiensis

  YU Daoping^1,2,3,4*, LI Cehong^2,3,4, LI Xiaojie^2,3,4, CHEN Xuling^2,3,4, XIE Kongping^1,2,3,4

  Guihaia. 2024, 44(1): 126-136. https://doi.org/10.11931/guihaia.gxzw202207014

  Abstract ( 40)   Knowledge map   Save

  Parakmeria omeiensis an evergreen tree belonged to Parakmeria of Magnoliaceae, is listed as a critically endangered plant under the first-grade State protection. Aimed to clarify the abortion period of male sterility in bisexual flowers of P. omeiensis and its physiological and biochemical characteristics, sterile stamens of bisexual flower and fertile stamens of male flower were test materials, the anther development was observed by paraffin section, the contents of soluble sugar, soluble protein, proline were determined, and catalase(CAT)and peroxidase(POD)activities were analyzed. The results were as follows:(1)Significant difference were detected in meiosis stage in anther development between sterile stamens and fertile stamens, the tapetum layer of sterile stamens was dense and undeveloped, the microspore mother cells didn't develop into the tetrad and subsequently disintegrated, so the pollen sac was empty. The tapetum layer and the microspore mother cells of fertile stamens developed normally, most pollen sac were broken and pollen grain were export.(2)The contents of soluble sugar, soluble protein, proline of sterile stamens were significantly lower than fertile stamens during the stages of meiosis, microspore monuclear and pollen mature.(3)POD activity of sterile stamens increased overall and was significantly higher than fertile stamens during the stages of meiosis, microspore monuclear and pollen mature. CAT activity of sterile stamens decreased as a whole and was significantly lower than fertile stamens in the same stage. We conclude that the microspore abortion occurs at the stage of meiosis, the decrease in metabolism of material and energy causes the abortion of male in bisexual flowers, the tapetum layer don't develop further and it doesn't provide nutrients to the microspore mother cells. CAT and POD activities are abnormal which results in the failure of timely scavenging free radicals in cells, and meiosis of microspore mother cells is blocked, so tetrads fail to be formed.
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  Dynamics of tissue nutrient content in relation to declining seedling growth in Malania oleifera

  CHEN Qiuping^1,2, LI Yunju³, LI Yue^1,2, XUE Ruijuan¹, LI Airong^1*

  Guihaia. 2024, 44(1): 137-146. https://doi.org/10.11931/guihaia.gxzw202303048

  Abstract ( 44)   Knowledge map   Save

  The decline in seedling growth of Malania oleifera as the age increases is often observed in the absence of host plants. A better knowledge of nutrient dynamics in terms of concentration and distribution patterns in different parts of the declining seedlings, the concentrations of N, P, and K were comparatively analyzed in various organs of unattached M. oleifera seedlings grown for half a year, two years, and three years. Additionally, the starch content and distribution patterns in the roots and stems of seedlings with different vigor levels were qualitatively assessed by staining cross-sections. The results were as follows:(1)As the growth vigor of M. oleifera seedlings declined, the concentrations of N, P, and K in most organs decreased, except for a significant increase in K concentration in lateral roots. The leaf N/P ratios of the declining seedlings became increasingly imbalanced, indicating different nutrient deficiency types among the seedlings with varying decline degrees. Unattached M. oleifera seedlings grown for half a year were primarily limited by insufficient N supply(with an average N/P ratio of 11.33)and subsequently by P limitation after two years(average N/P ratio 17.81). The leaf N/P ratio of unattached M. oleifera seedlings grown for three years was remarkably imbalanced(with an average value of 52.46). As the growth vigor of unattached three-year seedlings was considerably low, they are deemed unsuitable for afforestation.(2)A decrease in starch content was observed in declining seedlings, as evidenced by the reduced staining intensity of cross-sections. After three years, the starch content of unattached M. oleifera seedlings was found to have decreased to an extremely low level. Significant differences in starch content were observed at various locations, including the connecting point of the stems and roots, the basal swelling top of the root, the main root, and lateral roots, among seedlings with different degrees of decline. These findings suggested that starch content levels could serve as crucial criteria for evaluating the growth vigor of seedlings. Specifically, lateral roots were identified as optimal sampling materials for assessing seedling growth vigor through a minimally invasive method. Given the gradual decline in vitality and decreased nutrient content observed in M. oleifera seedlings grown in the absence of a host plant, it is recommended, during the propagation phase, to ensure adequate mineral nutrient supplementation, select appropriate host plants for cultivation, and facilitate early-stage transplantation. This proactive approach serves to mitigate a potential decline in survival rates during afforestation, attributed to the reduced vitality of the seedlings. The results of this study provide valuable information for evaluating seedling growth vigor and offer scientific guidance for rational fertilization in M. oleifera nurseries.
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  Effects of fertilization on young forest growth and leaf physiological characteristics of Toona ciliata var. pubescens

  PAN Junbin¹, LIU Yuansheng², ZHANG Lu^1*, CHENG Qiangqiang¹, WANG Jian², JIA Ting¹, WU Yunyan¹, GUO Chunlan¹

  Guihaia. 2024, 44(1): 147-156. https://doi.org/10.11931/guihaia.gxzw202211064

  Abstract ( 31)   Knowledge map   Save

  In order to explore the response of the precious tree species Toonaciliate var. pubescens to different amounts of different fertilizers, the young forest of T. ciliate var. pubescens was taken as the research object. A random block design was used to analyze the effects of fertilization on the growth, leaf nutrients and physiology of young forest of T. ciliate var. pubescens, and three fertilization levels(high, medium and low)were set, including nitrogenous fertilizer(N), phosphate fertilizer(P), compound fertilizer(CF)and slow-release fertilizer(SRF). The results were as follows:(1)Fertilization could promote the height and diameter at breast height(DBH)growth, and the effects of nitrogenous fertilizer and compound fertilizer were more obvious. The average tree height, average DBH and average volume of 4-year old tree with nitrogenous fertilizer increased by 15.0%, 21.9% and 67.5% compared with CK(no fertilizer), respectively, and the annual average growth of DBH under low nitrogenous fertilizer(N1)treatment was the highest(2.99 cm). Compared with CK, the average tree height, average DBH and average volume of compound fertilizer were increased by 16.7%, 19.2% and 54.3%, respectively. High slow-release fertilizer(SRF3)and low phosphate(P1)had the largest annual increases in tree height and DBH(1.96 m and 2.33 cm)in the 4th year, respectively.(2)Fertilization significantly increased chlorophyll content and non-structural carbohydrate content in leaves of T. ciliate var. pubescens, nitrogenous fertilizer significantly promoted the synthesis of soluble sugar and phosphate fertilizer significantly promoted the synthesis of starch.(3)N1 and phosphate fertilizer significantly promote the increase of N and P contents, respectively, and phosphate fertilizer, compound fertilizer and nitrogenous fertilizer significantly increased K content in leaves.(4)The principal component analysis showed that the effect of fertilizer to promote growth was nitrogenous fertilizer>compound fertilizer>phosphate fertilizer>slow-release fertilizer>no fertilizer. Among them, N1, i.e. 100 g·plant^-1·year^-1, had the highest comprehensive evaluation value. Comprehensive fertilization cost and benefit, nitrogenous fertilizer or compound fertilizer can effectively promote the growth and development of T. ciliate var. pubescens young forest. It is recommended to apply 100 g nitrogenous fertilizer per plant per year in young forest stage. The results can provide a reference for the forest nutrient management in the early stage of afforestation.
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  Pollination biology of the rare and endangered submerged plant, Ottelia cordata

  WANG Luanfeng^1,2, ZHANG Tongtong², XIANG Wenqian², LIANG Huiting¹, TAN Ke^3*, SHEN Yichun^1,2*

  Guihaia. 2024, 44(1): 157-166. https://doi.org/10.11931/guihaia.gxzw202212002

  Abstract ( 86)   Knowledge map   Save

  Ottelia cordata is a kind of rare and endangered submerged plant that grows in freshwater wetlands in northern Hainan Island, from Haikou to Wenchang in China. This species is known for its beautiful appearance and the distinct “flower river” landscape, which makes it a high ornamental value. With the intensification of human activities, the habitat of O. cordata has been sharply reduced and fragmented, leading to its endangerment. In order to explore the reproductive characteristics and reproductive laws of O. cordata, the flower morphology, sex ratio, pollen viability, stigma receptivity, reflectance spectrum, pollen limitation and apomixis, and the types and behaviors of pollinators in O. cordata were analyzed. That is, the pollination biology of O. cordata were studied for its further in-situ and ex-situ conservation. The results were as follows:(1)The flowers were dioecism, and the sex ratio of female and male individuals was about 1:2; the morphologies of male and female flowers were similar, and the female flowers were slightly larger than the male.(2) O. cordata had high pollen viability and stigma receptivity in budding and blooming phases.(3)Apis cerana was the main pollinator of Ottelia cordata, which visited male flowers more frequently than female flowers, with higher pollination efficiency.(4)The distance between the color loci of pistils and stamens was significantly higher than the discrimination threshold of Apis cerana.(5)The fruit setting percentage under natural pollination was similar to that under artificial pollination(95.29% and 98.42%, respectively), and there was no apomixis and low pollen limitation in the natural population of Ottelia cordata. In conclusion, the deceptive pollination of O. cordata simulated by both sexes is imperfect. Pollinators can visually distinguish female and male flowers. However, the large number of male flowers of O. cordata attracted many insects to visit flowers, which increases the probability of “mistake” pollination and is enough for the reproductive needs of female flowers. Therefore, future ex-situ conservation and artificial population restoration should pay more attention to population size, sex ratio and the number of local pollinators.
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  Ornamental plants of Orchidaceae and their functional groups in Beipan River basin of Guizhou

  HOU Huanhuan¹, AN Mingtai^2,3*

  Guihaia. 2024, 44(1): 167-178. https://doi.org/10.11931/guihaia.gxzw202203020

  Abstract ( 44)   Knowledge map   Save

  In order to protect and develop wild Orchidaceae(orchids)plant resources in Beipan River basin of Guizhou, scientifically screen high ornamental value orchids and explore their environmental adaptation characteristics, we took orchids distributing in Beipan River basin of Guizhou as the research project, selected species with high ornamental value based on analytic hierarchy process, and used clustering and redundancy analysis to identify the species composition of plant functional groups under different environmental conditions. The results were as follows:(1)There were 74 genera and 249 species(including varieties)of orchids, the horizontal spatial distribution was concentrated in two areas, namely the border area of Wangmo County and Ziyun County, and the western area of Panzhou City, repectively. The vertical spatial distribution showed an “intermediate expansion” with the change of altitude, the orchids were mainly distributed in the range of 800 -1 600 m.(2)Orchids in the study area could be divided into three ornamental grades, the first was the excellent grade for development, with 51 species, the second was the reserve grade for development, with 170 species, and the third had 28 species with low ornamental values, which were not necessary to be developed as ornamental plants.(3)Development optimal levels of ornamental orchids in the study area could be divided into four ecological function groups, which were low-altitude shade-requiring non-limestone mountain functional group, low-altitude heliophile limestone mountain functional group, intermediate-altitude shade-requiring limestone mountain functional group and high-altitude heliophile non-limestone mountain functional group, respectively. The types of adaptation of orchids to the environment varied greatly among different functional groups. All the above results indicate that screening high ornamental value orchids and dividing their ecological function groups is conducive to landscape application, scientific protection, introduction, domestication and development, and field regression of orchids in the future.
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  Population structure and number dynamic characteristics of endangered plant Ormosia hosiei in Sichuan and Guizhou provinces, China

  WANG Mingbin, WEI Xiaoli^*, WEI Yi, WANG Man, YU Dalong, YUAN Gangyi

  Guihaia. 2024, 44(1): 179-192. https://doi.org/10.11931/guihaia.gxzw202210038

  Abstract ( 51)   Knowledge map   Save

  Ormosia hosiei is a rare and endangered plant that is narrowly distributed in South China, with important economic and humanistic values. In order to find out its survival status and the reasons that restrict its development, we investigated the natural populations of O. hosiei in four regions of Guizhou and Sichuan provinces. According to the distributive characteristics of different populations, we set up two 20 m × 20 m for each population by using the method of plot investigation and conducted a community survey in each plot. The structural characteristics of O. hosiei populations were analyzed by establishing population static life tables and drawing populations survival curves. Four survival functions, number dynamic index, and time series model analysis were used to describe survival status. The results were as follows:(1)The age-class structure of O. hosiei populations were in the shape of “J”at Hezhu Village and Ganerpan Village, in the shape of “Dumbbell”at Chenjiawan Village and Rongchun Village, the populations had strong natural renewal ability, but middle-aged individuals were easily missing.(2)The four populations belonged to the increasing type, the survival curves of populations are close to Type Deevey-Ⅱ, the disappearance rate and mortality rate of O. hosiei populations showed a “Multimodal” pattern in Hezhu Village, Chenjiawan Village and Rongchun Village, indicating that the populations were susceptible to external disturbances in the middle period.(3)All O. hosiei populations in different regions appeared to decrease in the early stage and keep dynamically stable in the medium-late stage, and the formation reasons were related to the topographic characteristics of mountainous areas and the seed dispersal characteristics of O. hosiei.(4)RDA analysis showed that altitude and slope were the dominant factors affecting the populations structure of young individuals, and interference intensity was the main factor affecting the number structure of older individuals. All the above results indicate that the structural and number characteristics of O. hosiei populations in different regions are restricted by the topographic characteristics of mountainous areas, the reproductive characteristics of O. hosiei and the environmental pressure; By controlling the density of young individuals and managing the growth space of middle-aged individuals, we can increase the survival rate of the seedlings, promote the healthy growth of middle-aged individuals, and maintain the stability of the natural populations of O. hosiei.
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  Advances on taxonomy and breeding of Saxifraga Tourn. ex L.

  TANG Shimei^1,2,3,4, ZHANG Xia^2,4, CHEN Qianru^2,4, CAI Wenqi^2,4, LI Yanlin^2,4, TIAN Daike^1,3*

  Guihaia. 2024, 44(1): 193-206. https://doi.org/10.11931/guihaia.gxzw202212037

  Abstract ( 43)   Knowledge map   Save

  Saxifraga Tourn. ex L. is rich in species diversity with about 440-500 species and broad distribution. The taxonomical issues of this genus have been continuously concerned by the botanists. Saxifraga has important ornamental and medicinal values. Some of European countries have made great efforts on the exploitation and utilization of its ornamental resources. China is one of the diversity centers of Saxifraga, but it has been lagged far behind Europe, USA and even Japan in exploitation and utilization on ornamental value of this genus. The world breeding work in Saxifraga started 150 years ago. By the end of 2022, the 1 692 names of cultivars had been on-line listed by The Saxifrage Society, but only one came from China. In this paper, the germplasm resources of Saxifraga, and progress on its classification and breeding are reviewed, and also the utilization of its ornamental resources is briefly introduced, which will provide an important reference for taxonomical research, breeding and application of this genus in China. The results are as follows:(1)Saxifraga is rich in germplasms, but many scientific issues remain in the evolutionary relationships of its subordinate systems, which require a systematic and in-depth investigation by integrating morphological and molecular biology methods.(2)The cultivars of this genus are mainly raised through cross-breeding and mutant selection, and the majority of cultivars are from the UK, Czech Republic, Germany, and the Netherlands.(3)The breeding of Saxifraga started very late in China, with only few cultivars from one breeding method.