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25 June 2020, Volume 42 Issue 03
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  • Articles
    A new subtribal classification of Arundinarieae (Poaceae, Bambusoideae) with the description of a new genus
    Yu-Xiao Zhang, Cen Guo, De-Zhu Li
    2020, 42(03):  127-134.  doi:10.1016/j.pld.2020.03.004
    Abstract ( 321 )   HTML ( )   PDF (1624KB) ( 154 )   Save
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    A new subtribal classification of the woody bamboo tribe Arundinarieae is proposed based on recent phylogenomic studies. Five subtribes, corresponding to the five major lineages of the ddRAD-seq based phylogenomic trees, are recognised: Arundinariinae (the leptomorph lineage), Ampelocalaminae (the ADH lineage), Gaoligongshaniinae (represented by Gaoligongshania), Hsuehochloinae (represented by Hsuehochloa) and Thamnocalaminae (the pachymorph lineage, i.e., alpine bamboos). Subtribes Ampelocalaminae, Gaoligongshaniinae and Hsuehochloinae are newly established, while the circumscriptions of subtribes Arundinariinae and Thamnocalaminae differ from the traditional classification. Subtribe Arundinariinae also includes those taxa that were previous members of the subtribe Shibataeinae. Thus, among the five redefined subtribes, Arundinariinae is the most heterogenous in terms of morphology. In Arundinarieae, rhizome type has greater implications for classification than other vegetative and reproductive characters at the subtribal level. In addition, the new monotypic genus Ravenochloa is described on the basis of its morphological characteristics and geographical distribution to accommodate the unique phylogenetic entity of Indocalamus wilsonii.
    Karyomorphology of three endemic plants (Brassicaceae: Euclidieae and Arabideae) from the Qinghai-Tibet Plateau and its significance
    Wenguang Sun, Haixia Wang, Rui Wu, Hang Sun, Zhimin Li
    2020, 42(03):  135-141.  doi:10.1016/j.pld.2020.03.002
    Abstract ( 212 )   HTML ( )   PDF (1207KB) ( 63 )   Save
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    In the paper, chromosome number and karyotype of three endemic genera from China are reported for the first time. Our results show that Anzhengxia yechengnica has a karyotype formula 2n=2x=14=6 m+8sm and belongs to Stebbins-3A; Shangrilaia nana karyotype formula is 2n=2x=14=10 m+4sm (2sat) and belongs to Stebbins-1A; Baimashania pulvinata karyotype formula is 2n=2x=16=12 m (2sat)+4sm and belongs to Stebbins-1A. Anzhengxia and Shangrilaia are monospecific genera belonging to tribe Euclidieae and both have a basic chromosome x=7. Baimashania, which belongs to tribe Arabideae, has two species which have a basic chromosome x=8. The implications of these cytological data are compared with morphological support and the implications for each tribe are discussed. We also summarize chromosomal number variation and its systematic implications of two tribes from the Qinghai-Tibet Plateau.
    Both small and large plants are likely to produce staminate (male) flowers in a hermaphrodite lily
    EiEi Shwe, Bo Wu, Shuang-Quan Huang
    2020, 42(03):  142-147.  doi:10.1016/j.pld.2020.01.004
    Abstract ( 255 )   HTML ( )   PDF (940KB) ( 24 )   Save
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    Resource allocation to female and male function may vary among individual plants in species with variable sex expression. Size-dependent sex allocation has been proposed in hermaphrodites, in which female-biased allocation may increase with plant size. In many hermaphrodites with large floral displays, however, later-produced flowers tend to be functionally male. This paradoxical relationship between female and male function and plant size remains poorly understood. The subalpine lily Lilium lankongense has individuals of three sexual types: males with only staminate flowers, hermaphrodites with only perfect flowers, and andromonoecious plants with both perfect and staminate flowers. Here we tested theoretical predictions of size-dependent sex allocation in L. lankongense by measuring plant height and flower number of individuals of each sex at five field sites in the mountainous region of Shangri-La, southwestern China. To investigate variation in phenotypic gender, we identified sex expression of 457 individuals one year later. Our investigation showed that male plants, which usually produced one flower, were significantly smaller than andromonoecious and hermaphrodite plants. In addition, the total flower numbers of andromonoecious and hermaphrodite plants increased significantly with plant size. Large individuals were more likely to produce terminal staminate flowers, as there were more flowers in andromonoecious than in hermaphrodite individuals. Non-flowered plants were significantly smaller than flowering ones. Perfect flowers had significantly larger petals and pistils than staminate flowers, but they did not differ in dry weight of stamens. Our findings indicate that when plants are small, the less costly sex is favored, consistent with the ‘size-advantage hypothesis’. When plants are large, both female and male investments change isometrically, as later-produced flowers tend to be functionally male.
    Asian monsoon shaped the pattern of woody dicotyledon richness in humid regions of China
    Wen-Yun Chen, Tao Su
    2020, 42(03):  148-154.  doi:10.1016/j.pld.2020.03.003
    Abstract ( 157 )   HTML ( )   PDF (2207KB) ( 33 )   Save
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    Understanding how geographical patterns of plant richness are established is a key scientific question in ecology and biogeography. Climate factors, such as environmental energy, water availability, and rainfall seasonality, have been widely proposed to account for geographical patterns of plant richness at large scales. Using a compiled distribution data set of 3166 native woody dicotyledons across 732 calibration grids at the county level in humid regions of China, we explored the geographical pattern of woody dicotyledon richness and its relationship to climatic variations, especially the Asian monsoonal climate. We found that species richness decreases with increasing latitude. Our study indicates that water availability (particularly mean annual precipitation, MAP) is the major abiotic factor in determining large-scale distribution patterns of species richness. Moreover, the seasonality of rainfall variables under the Asian monsoon climate largely contributes to species richness, because species richness correlates more significantly with precipitation during the three driest consecutive months (P3DRY) than precipitation during the three wettest consecutive months (P3WET). Therefore, we conclude that woody dicotyledon richness in humid regions of China is mainly affected by the Asian winter monsoon.
    Involucre fossils of Carpinus, a northern temperate element, from the Miocene of China and the evolution of its species diversity in East Asia
    Li Xue, Linbo Jia, Gi-soo Nam, Yongjiang Huang, Shitao Zhang, Yuqing Wang, Zhuo Zhou, Yongsheng Chen
    2020, 42(03):  155-167.  doi:10.1016/j.pld.2020.01.001
    Abstract ( 203 )   HTML ( )   PDF (6785KB) ( 51 )   Save
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    East Asia has long been recognized as a major center for temperate woody plants diversity. Although several theories have been proposed to explain how the diversity of these temperate elements accumulated in the region, the specific process remains unclear. Here we describe six species of Carpinus, a typical northern hemisphere temperate woody plant, from the early Miocene of the Maguan Basin, southwestern China, southern East Asia. This constitutes the southernmost, and the earliest occurrence that shows a high species diversity of the genus. Together with other Carpinus fossil records from East Asia, we show that the genus had achieved a high diversity in East Asia at least by the middle Miocene. Of the six species here described, three have become extinct, indicating that the genus has experienced apparent species loss during its evolutionary history in East Asia. In contrast, the remaining three species closely resemble extant species, raising the possibility that these species may have persisted in East Asia at least since the early Miocene. These findings indicate that the accumulation of species diversity of Carpinus in East Asia is a complex process involving extinction, persistence, and possible subsequent speciation.
    Cold stratification, temperature, light, GA3, and KNO3 effects on seed germination of Primula beesiana from Yunnan, China
    Li-E Yang, De-Li Peng, Zhi-Min Li, Li Huang, Juan Yang, Hang Sun
    2020, 42(03):  168-173.  doi:10.1016/j.pld.2020.01.003
    Abstract ( 200 )   HTML ( )   PDF (767KB) ( 52 )   Save
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    Primula beesiana Forr. is an attractive wildflower endemically distributed in the wet habitats of subalpine/alpine regions of southwestern China. This study is an attempt to understand how this plant adapts to wet habitats and high altitudes. Specifically, we examined the effects of cold stratification, light, GA3, KNO3, and temperature on P. beesiana seed germination. KNO3 and GA3 increased germination percentage and germination rate compared to control treatments at 15/5 and 25/15 ℃. Untreated seeds germinated well (> 80%) at higher temperatures (20, 25 and 28 ℃), whereas at lower (5, 10 and 15 ℃) and extremely high temperatures (30 and 32 ℃) germination decreased significantly. However, after cold stratification (4-16 weeks), the germination percentage of P. beesiana seeds at low temperatures (5-15 ℃) and the germination rate at high temperatures (30 ℃) increased significantly, suggesting that P. beesiana has type 3 non-deep physiological dormancy. The base temperature and thermal time for germination decreased in seeds that were cold stratified for 16 weeks. Cold-stratified seeds incubated at fluctuating temperatures (especially at 15/5 ℃) had significantly high germination percentages and germination rates in light, but not in dark, compared to the corresponding constant temperature (10 ℃). Seeds had a strict light requirement at all temperatures, even after experiencing cold stratification; however, the combinations of cold stratification and fluctuating temperature increased germination when seeds were transferred from dark to light. Such dormancy/germination responses to light and temperature are likely mechanisms that ensure germination occurs only in spring and at/near the soil surface, thus avoiding seedling death by freezing, inundation and/or germination deep in the soil.
    The leaf extract of crofton weed (Eupatorium adenophorum) inhibits primary root growth by inducing cell death in maize root border cells
    Jinhu Ma, Xinxin Feng, Xiaohuan Yang, Yongheng Cao, Weifeng Zhao, Liangliang Sun
    2020, 42(03):  174-180.  doi:10.1016/j.pld.2020.02.001
    Abstract ( 192 )   HTML ( )   PDF (1583KB) ( 36 )   Save
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    The extract of crofton weed (Eupatorium adenophorum) inhibits seed germination and weed growth; however, the physiological mechanisms underlying the effect of crofton weed extract on the modulation of seedling growth and root system development remain largely unclear. In this study, we investigated the effects of the leaf extract of crofton weed (LECW) on primary root (PR) growth in maize seedlings. Treatment with LECW markedly inhibited seed germination and seedling growth in a dose-dependent manner. Physiological analysis indicated that the LECW induced reactive oxygen species (ROS) accumulation in root tips, thereby leading to cell swelling and deformation both in the root cap and elongation zone of root tips, finally leading to cell death in root border cells (RBCs) and PR growth inhibition. The LECW also inhibited pectin methyl esterase (PME) activity, thereby decreasing the RBC number. Taken together, our results indicated that the LECW inhibited PR growth by inducing ROS accumulation and subsequent cell death in RBCs. The present study provides a better understanding of how the LECW modifies root system development and provides insight for evaluating the toxicity of crofton weed extracts in plants.
    Differences in leaf physiological and morphological traits between Camellia japonica and Camellia reticulata
    Ji-Hua Wang, Yan-Fei Cai, Shi-Feng Li, Shi-Bao Zhang
    2020, 42(03):  181-188.  doi:10.1016/j.pld.2020.01.002
    Abstract ( 253 )   HTML ( )   PDF (1380KB) ( 68 )   Save
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    Plants of the genus Camellia are widely cultivated throughout the world as ornamentals because of their bright and large flowers. The widely cultivated varieties are mainly derived from the mutant lines and hybrid progenies of Camellia japonica Linn. and Camellia reticulata Lindl. While their geographical distributions and environmental adaptabilities are significantly different, no systematic comparison has been conducted between these two species. To investigate differences in how these plants have adapted to their environments, we measured photosynthesis and 20 leaf functional traits of C. japonica and C. reticulata grown under the same conditions. Compared with C. japonica, C. reticulata showed higher values for light saturation point, light-saturated photosynthetic rate, leaf dry mass per unit area and stomatal area, but lower values for apparent quantum efficiency, leaf size, stomatal density and leaf nitrogen content per unit mass. Stomatal area was positively correlated with light-saturated photosynthetic rate and light saturation point, but negatively correlated with stomatal density. The differences between C. reticulata and C. japonica were mainly reflected in their adaptations to light intensity and leaf morphological traits. C. reticulata is better adapted to high light intensity than C. japonica. This difference is related to the two species’ differing life forms. Thus, leaf morphological traits have played an important role in the light adaptation of C. reticulata and C. japonica, and might be first noticed and selected during the breeding process. These findings will contribute to the cultivation of camellia plants.
    Genetic structure, gene flow pattern, and association analysis of superior germplasm resources in domesticated upland cotton (Gossypium hirsutum L.)
    Ting-Ting Zhang, Na-Yao Zhang, Wei Li, Xiao-Jian Zhou, Xiao-Yu Pei, Yan-Gai Liu, Zhong-Ying Ren, Kun-Lun He, Wen-Sheng Zhang, Ke-Hai Zhou, Fei Zhang, Xiong-Feng Ma, Dai-Gang Yang, Zhong-Hu Li
    2020, 42(03):  189-197.  doi:10.1016/j.pld.2020.03.001
    Abstract ( 225 )   HTML ( )   PDF (478KB) ( 57 )   Save
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    Gene flow patterns and the genetic structure of domesticated crops like cotton are not well understood. Furthermore, marker-assisted breeding of cotton has lagged far behind that of other major crops because the loci associated with cotton traits such as fiber yield and quality have scarcely been identified. In this study, we used 19 microsatellites to first determine the population genetic structure and patterns of gene flow of superior germplasm resources in upland cotton. We then used association analysis to identify which markers were associated with 15 agronomic traits (including ten yield and five fiber quality traits). The results showed that the upland cotton accessions have low levels of genetic diversity (polymorphism information content =0.427), although extensive gene flow occurred among different ecological and geographic regions. Bayesian clustering analysis indicated that the cotton resources used in this study did not belong to obvious geographic populations, which may be the consequence of a single source of domestication followed by frequent genetic introgression mediated by human transference. A total of 82 makeretrait associations were examined in association analysis and the related ratios for phenotypic variations ranged from 3.04% to 47.14%. Interestingly, nine SSR markers were detected in more than one environmental condition. In addition, 14 SSR markers were co-associated with two or more different traits. It was noteworthy that NAU4860 and NAU5077 markers detected at least in two environments were simultaneously associated with three fiber quality traits (uniformity index, specific breaking strength and micronaire value). In conclusion, these findings provide new insights into the population structure and genetic exchange pattern of cultivated cotton accessions. The quantitative trait loci of domesticated cotton identified will also be very useful for improvement of yield and fiber quality of cotton in molecular breeding programs.
    New insights into the evolutionary history of Megacodon: Evidence from a newly discovered species
    Jun-Chu Peng, Xiang-Guang Ma, Yue-Hua Wang, Hang Sun
    2020, 42(03):  198-208.  doi:10.1016/j.pld.2020.05.003
    Abstract ( 252 )   HTML ( )   PDF (2976KB) ( 110 )   Save
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    Megacodon is an ideal genus to study speciation and ecological adaptation in the Sino-Himalayan region. The genus contains two species distributed at different elevations and in two separate areas. However, studies of this genus have long been impeded by a lack of fieldwork on one of its species, Megacodon venosus. In this study, we collected specimens of two Megacodon species and found an extraordinary new species of Megacodon in Lushui county of north-west Yunnan province, which we have since named Megacodon lushuiensis. We propose new species based on both morphological and molecular evidence. The finding of this new species emphasized the importance of ecological divergence in the divergence of Megacodon stylophorus and its parapatric low-elevation Megacodon species. To identify genetic determinants that underlie adaptations to different elevations, we characterized transcriptomes of the new species M. lushuiensis, which is distributed at low elevations, and M. stylophorus, which is distributed at high elevations. Comparative transcriptome analysis identified 8926 orthogroups containing single-copy genes, and 370 orthogroups containing significantly positively selected genes. The set of positively selected genes was enriched into 25 Gene Ontology terms, including “response to water deprivation”, “response to osmotic stress”, and “cellular response to external stimulus”. Our results provide new insights into how ecological adaptation and speciation occurred in Megacodon and highlight the role of heterogeneous habitats in the speciation of plants in the Sino-Himalayan region.