孟仁草的花序发育研究

在光学显微镜和扫描电镜下观察了禾本科(Poaceae)虎尾草属(Chloris Sw.)孟仁草(Chloris barbata Sw.)的花序发育过程,以寻找适于虎尾草群(Chloris group)分支分析的发育性状.结果发现了未见于成熟花序的23个发育性状.阐明盂仁草花序的本质是二级长侧枝包围平截的主轴构成指形花序.该类型花序仅见于单子叶植物和少数高度特化的双子叶植物.涉及花序分枝的分子遗传机制研究亟待开展.     

禾本科虎尾草亚科细胞学研究分析

总结了虎尾草亚科72属601个分类单位的细胞学资料。虎尾草亚科的染色体基数是10和9,来源于原始染色体基数6经非整倍性减少为5,再经多倍化及非整倍性减少而来。细胞学性状对虎尾草亚科属上类群的分类具有相当重要的价值。推测染色体基数演化的趋势为:x=6→x=5→x=10→x=9。据认为,虎尾草亚科的原始染色体基数为5的二倍体类群在演化早期就灭绝了。     

A molecular phylogeny and classification of Leptochloa (Poaceae: Chloridoideae: Chlorideae) sensu lato and related genera

Background and Aims

Leptochloa (including Diplachne) sensu lato (s.l.) comprises a diverse assemblage of C₄ (NAD-ME and PCK) grasses with approx. 32 annual or perennial species. Evolutionary relationships and a modern classification of Leptochloa spp. based on the study of molecular characters have only been superficially investigated in four species. The goals of this study were to reconstruct the evolutionary history of Leptochloa s.l. with molecular data and broad taxon sampling.

Methods

A phylogenetic analysis was conducted of 130 species (mostly Chloridoideae), of which 22 are placed in Leptochloa, using five plastid (rpL32-trn-L, ndhA intron, rps16 intron, rps16-trnK and ccsA) and the nuclear ITS 1 and 2 (ribosomal internal transcribed spacer regions) to infer evolutionary relationships and revise the classification.

Key results

Leptochloa s.l. is polyphyletic and strong support was found for five lineages. Embedded within the Leptochloa sensu stricto (s.s.) clade are two Trichloris spp. and embedded in Dinebra are Drake-brockmania and 19 Leptochloa spp.

Conclusions

The molecular results support the dissolution of Leptochloa s.l. into the following five genera: Dinebra with 23 species, Diplachne with two species, Disakisperma with three species, Leptochloa s.s. with five species and a new genus, Trigonochloa, with two species.     

A biogeographical analysis of Muhlenbergia (Poaceae: Chloridoideae: Cynodonteae: Muhlenbergiinae)

A phylogeny based on the analysis of six DNA sequence markers (ITS, ndhA intron, rpl32-trnL, rps3, rps16 intron, and rps16-trnK) is used to infer ancestral areas and divergence times, and reconstruct the biogeographical history and evolution of 150 of the 183 (82%) species of Muhlenbergia. Our results suggest that the genus originated 9.3 mya in the Sierra Madre (Occidental and Oriental) in Mexico, splitting into six lineages: M. ramulosa diverging 8.2 mya, M. subg. Muhlenbergia at 5.9 mya, M. subg. Pseudosporobolus at 5.9 mya, M. subg. Clomena at 5.4 mya, M. subg. Bealia at 4.3 mya, and M. subg. Trichochloa at 1 mya, each of these with a high probability of Sierra Madrean origin. Our results further suggest that founder-event speciation from Sierra Madre to South America occurred independently multiple times in all five subgenera during the Pleistocene and late Pliocene. One long-distance dispersal event most likely originating from Central or Eastern North America to East and Central Asia occurred 1.6–1 mya in M. subg. Muhlenbergia. In our cladogram, members of M. subg. Trichochloa show little genetic resolution, suggesting very low levels of divergence among the species, and this may be a consequence of rapid radiation.     

E/Z-Thesinine-O-4'-alpha-rhamnoside, pyrrolizidine conjugates produced by grasses (Poaceae)

Based on direct infusion mass spectrometry we identified a novel alkaloid as a major component of perennial ryegrass (Lolium perenne). Initial mass spectral data suggested it to be a pyrrolizidine conjugate. As this class of alkaloids has not been described before from grasses, we isolated it to elucidate its structure. The isolated alkaloid proved to be a mixture of two stereoisomers. The structures of the two compounds as determined by 1D and 2D NMR spectroscopy, were E-thesinine-O-4'-alpha-rhamnoside (1) and Z-thesinine-O-4'-alpha-rhamnoside (2). These identifications were supported by the characterisation by GC-MS and optical rotation of (+)-isoretronecanol as the necine base released on alkaline hydrolysis of these alkaloids. 1 and 2 together with the aglycone and a hexoside were also detected in tall fescue (Festuca arundinacea). This is the first report of pyrrolizidine alkaloids produced by grasses (Poaceae).     

Inflorescence structure in species of Spartina Schreb. (Poaceae: Chloridoideae: Cynodonteae)

The typology developed by Troll was followed to describe inflorescence structures for 15 species of Spartina. In all species here studied, truncation of the terminal spikelet of the main axis and primary paracladium was observed. The truncation can also involve the short paracladia subzone so that the inflorescence is confined to just the long paracladia subzone. A great homogenization of paracladia and maximum ramification degree limited generally to the second order of branching are distinctive characteristics of the genus. Proximal paracladia with third-order branching were found in only three specimens, and in these exceptional cases, the homogenization is partial. Sometimes, in some species, a subzone of long and short paracladia can be distinguished. The absence of trophotagma paracladia in all the species studied was verified. The variation in the structure of the inflorescence among species is due to the differences in the number of short paracladia, long paracladia, total number of primary paracladia and also in the angle of divergence of the long paracladia from the main axis. The latter, in addition to variations in the intercalary growth of the internodes produces modifications in the general appearance of the inflorescences. The systematic and taxonomic value of the inflorescences in Spartina is discussed.     

Allotetraploid origin and divergence in Eleusine (Chloridoideae, Poaceae): evidence from low-copy nuclear gene phylogenies and a plastid gene chronogram

Background and Aims Eleusine

(Poaceae) is a small genus of the subfamily Chloridoideae exhibiting considerable morphological and ecological diversity in East Africa and the Americas. The interspecific phylogenetic relationships of Eleusine are investigated in order to identify its allotetraploid origin, and a chronogram is estimated to infer temporal relationships between palaeoenvironment changes and divergence of Eleusine in East Africa.

Methods

Two low-copy nuclear (LCN) markers, Pepc4 and EF-1α, were analysed using parsimony, likelihood and Bayesian approaches. A chronogram of Eleusine was inferred from a combined data set of six plastid DNA markers (ndhA intron, ndhF, rps16-trnK, rps16 intron, rps3, and rpl32-trnL) using the Bayesian dating method.

Key Results

The monophyly of Eleusine is strongly supported by sequence data from two LCN markers. In the cpDNA phylogeny, three tetraploid species (E. africana, E. coracana and E. kigeziensis) share a common ancestor with the E. indica–E. tristachya clade, which is considered a source of maternal parents for allotetraploids. Two homoeologous loci are isolated from three tetraploid species in the Pepc4 phylogeny, and the maternal parents receive further support. The A-type EF-1α sequences possess three characters, i.e. a large number of variations of intron 2; clade E-A distantly diverged from clade E-B and other diploid species; and seven deletions in intron 2, implying a possible derivation through a gene duplication event. The crown age of Eleusine and the allotetraploid lineage are 3·89 million years ago (mya) and 1·40 mya, respectively.

Conclusions

The molecular data support independent allotetraploid origins for E. kigeziensis and the E. africana–E. coracana clade. Both events may have involved diploids E. indica and E. tristachya as the maternal parents, but the paternal parents remain unidentified. The habitat-specific hypothesis is proposed to explain the divergence of Eleusine and its allotetraploid lineage.     

Lemma micromorphological characters in the Chloridoideae (Poaceae) optimized on a molecular phylogeny

Eight lemma micromorphological characters of 83 taxa representing 61 genera in the Chloridoideae have been investigated using Scanning Electron Microscopy, including long cells, cork cells, stomata, bicellular microhairs, papillae, silica cells, microprickles, and macrohairs. Five new types of lemma micromorphological characters were reported here. Data for 27 taxa representing 19 genera from previous publications were also supplied to access the homology of lemma micromorphological characters for different groups through optimization onto a molecular cladogram. Given the optimization, five characters including long cells, cork cells, stomata, papillae, microprickles are of phylogenetic significance for supra-generic groups. Seven characters including straight outline long cells, crescent-shaped cork cells, absent stomata, absent papillae, dumb-bell-shaped silica cells, c-type microprickles, and papillate-base macrohairs may not be homologous, however, the enneapogonoid-type bicellular microhairs appeared as a synapomorphy for the Chloridoideae.     

中国禾本科植物新资料(I)

报道了2种禾本科植物,曲序黄花茅[Anthoxanthum flexuosum（Hook.f.）Veldkamp]在西藏的新分布,外来物种弗吉尼亚须芒草（Andropogon virginicus L.）在江西的归化,并提供了它们详细的形态学描述、图版、分布及生境等信息。此外,还讨论了弗吉尼亚须芒草的潜在入侵危险。     

Phylogenetic relationships among Southeast Asian climbing bamboos (Poaceae: Bambusoideae) and the Bambusa complex

A phylogenetic analysis of Bambusa and allies based on the plastid DNA non-coding regions rps16-trnQ, trnC-rpoB, trnH-psbA and trnD-T, and a partial nuclear GBSSI gene, was carried out. This included representatives from all four Bambusa subgenera (including type species), a group of segregate Southeast Asian genera distinctive by their climbing–scrambling culms (Dinochloa, Holttumochloa, Kinabaluchloa, Maclurochloa, Soejatmia, Sphaerobambos), and two other Bambusinae genera (Dendrocalamus, Gigantochloa). The results do not support the present subgeneric classification of Bambusa. The climbing Southeast Asian genera, all of which include species previously placed in Bambusa, are distinct from the “core Bambusa group” (type species and alliance) and the Bambusa complex generally.     

广东省五节芒遗传多样性的ISSR分析

采用ISSR分子标记技术,对广东省内分布的能源植物五节芒(Miscanthus floridulus)13个野生居群共215个个体的遗传多样性进行了研究.9个ISSR引物共扩增到了81个位点,其中76个是多态性位点.结果表明,广东五节芒的遗传多样性水平很高,物种水平上,多态位点百分率(PPB)为93.83％,Nei's...     

Organogenesis of Fascicled ear mutant inflorescences in maize (Poaceae)

The ontogeny of staminate tassels and pistillate ears in the maize mutant Fascicled ear was examined using scanning electron microscopy. The normal pattern of inflorescence development is perturbed by the Fascicled ear mutation at the transition stage. The Fascicled ear mutation promotes the development of an abnormal transition stage axis that is both shorter and broader than the wild type. The inflorescence apical meristem then undergoes a bifurcation, and two inflorescence axes arise in place of a single axis. Each derived inflorescence apical meristem may undergo a similar perturbation sequence. This expression of the Fascicled ear mutation may be repeated one to several times, which leads to the development of a fascicled pistillate inflorescence and a fascicled central spike in the staminate inflorescence. The apical meristems of some tassel branches are also bifurcated. Subsequent organogenesis during paired-spikelet and floral development in Fascicled ear plants follows the pattern of normal maize. However, triplet spikelets are occasionally observed. The organogenic disruption by the Fascicled ear mutation that we describe will aid genetic and molecular analysis on the regulation of inflorescence development in maize and other members of the genus Zea.     

Atypical foliar anatomy related to Kranz syndrome in Paspalum inaequivalve and Paspalum microstachyum (Poaceae: Panicoideae: Paniceae)

Paspalum L. is a large and complex genus, enclosing more than 300 species, whose boundaries and infrageneric classification are still being studied. Recent phylogenetic analyses suggest that Paspalum inaequivalve Raddi and Paspalum microstachyum J. Presl, from the Inaequivalvia informal group, should be excluded from Paspalum. Focused on the unclear taxonomic position of P. inaequivalve and P. microstachyum, their leaf anatomy was studied, and some atypical features related to C₄ photosynthesis were found. This atypical Kranz syndrome is the aim of this research. Transverse leaf blade sections from fresh and herbarium material of P. inaequivalve were studied by light, fluorescence, and transmission microscopy. Additionally, sheaths and culms of P. inaequivalve and leaf blades of P. microstachyum were observed by light microscopy. δ¹³C isotope discrimination was determinated for P. inaequivalve. We compared our results with available anatomical data from related taxa. As well as typical mesophyll cells (PCA) and mestome sheath cells (PCR), a third type of cells, here called ‘globose parenchymatous cells’, was observed in leaf blades of P. inaequivalve and P. microstachyum. These cells are placed externally to the mestome sheaths of the first and second vascular bundles, they have thin walls, with no developed suberine lamella, few chloroplasts with 1–2 starch grains, thylakoids not organized in grana, and a large central vacuole. The globose parenchymatous cells represent a novel trait in P. inaequivalve and P. microstachyum, further supporting the close relation between both species and their exclusion from the genus Paspalum. This atypical Kranz syndrome has not been described in Paspalum before, but the globose parenchymatous cells here described resemble the distinct cells considered as remnants of the outer parenchymatous sheath described for Anthaenantiopsis, some sections of Panicum L., and Chaetium Nees, providing possible taxonomic significance.     

Molecular evolution of the maize sex-determining gene TASSELSEED2 in Bouteloua (Poaceae)

The majority of angiosperms produce hermaphrodite flowers, while a lesser number (20–30%) produce unisexual flowers. Little is known about the molecular biology of sex-determination in angiosperms, however, a few sex-determining genes have been cloned from the model system Zea mays. One of these genes is Tasselseed2 (Ts2) which has been shown to be involved in the arrest of developing pistils in male flowers. In this study, we sequenced a putative homologue of Ts2 in species of Bouteloua, a genus in the grass subfamily Chloridoideae. We found significant genetic variation at Ts2 in Bouteloua relative to other developmental genes characterized in maize and other grass species. We also found that in Bouteluoua, Ts2 is evolving non-neutrally in the hermaphrodite-flowered Bouteloua hirsuta while no difference from neutral expectation was detected at Ts2 in the monoecious/dioecious Bouteloua dimorpha. The putatively neutral gene Alcohol Dehydrogenase1 (Adh1) was also examined for the same species of Bouteloua, and no departure from neutral expectation was detected. Our results suggest that purifying selection may be acting on Ts2 in the hermaphrodite-flowered B. hirsuta while no evidence of selection was detected at Ts2 in the monoecious/dioecious B. dimorpha.     

赖草属植物的分类现状及主要存在的问题

赖草属(Leymus Hochst.)为禾本科(Poaceae)小麦族(Triticeae)中的一个有重要经济价值的属,属内多数种类是优良牧草,有些种类具有耐寒、耐旱、耐碱等特性,是农业良种繁育、畜牧业牧草改良利用的重要基因资源。该属在分类学上是一个疑难属,在属的界限、属下组系的划分,以及类群间演化关系上问题较多。对赖草属分类学问题进行了综述,为赖草属植物资源的开发利用和保护提供资料。     

高粱属植物的地理分布

为探讨高粱属(Sorghum Moench)的系统发育关系,通过野外调查及查阅标本和文献资料,对高粱属植物的地理分布进行了整理和研究。高粱属植物约有29种,分布于全世界热带到温带地区,其中澳大利亚22种,亚洲15种,非洲9种,欧洲3种,地中海2种,美洲6种。中国有5种,分布在东北、西南到华南各省(区)。高粱属有5亚属,仅高粱亚属(subgen.Sorghum)延伸至新世界,其他亚属均分布在旧世界,高粱亚属覆盖非洲并扩散到全世界热带到温带地区;拟高粱亚属(subgen.Parasorghum)分布在非洲、亚洲、澳大利亚;有柄高粱亚属(subgen.Stiposorghum)主要分布在澳大利亚,个别种分布到亚洲;多毛高粱亚属(subgen.Chaetosorghum)分布在澳大利亚;异高粱亚属(subgen.Heterosorghum)分布在澳大利亚和亚洲。这表明澳大利亚东北部是高粱属的现代分布中心和多样化中心,非洲东北部和热带亚洲是否是高粱属的起源地尚需确证。