Acetylated tubulin is found in all microtubule arrays of two species of pine

Summary The distribution of acetylated tubulin in microtubule arrays of conifer cells was investigated by immunofluorescence techniques with 6-11B-1, a monoclonal antibody specific for posttranslationally acetylated -tubulins. In methacrylate sections ofPinus radiata andPinus conforta root tip cells, acetylated tubulin was detected in mitotic spindles, phragmoplasts, and cortical microtubules. Furthermore, staining of isolated, intact cells ofP. radiata andP. contorta indicated that all microtubule structures, including preprophase bands, prophase, metaphase and anaphase spindles, and phragmoplasts, contained some acetylated tubulin, and that the intensity of staining with 6-11B-1 was variable. For example, preprophase bands were lightly labelled, kinetochore fibres of anaphase spindles and phragmoplasts were heavily stained, and metaphase spindles had a granular appearance suggesting discontinuous acetylation of their constituent microtubules. This first report of the presence of acetylated tubulin in conifer cells is in contrast to our results with two species of angiosperms where no acetylated tubulin was detected. The significance of this and the variability of the intensity of staining in conifer arrays is discussed in terms of microtubule dynamics.     

Prepollination degeneration in mature synergids of pearl millet: an examination using antimonate fixation to localize calcium

Summary The pattern of degeneration in mature synergids of pearl millet prior to pollination was examined by transmission electron microscopy after conventional and antimonate fixation to precipitate loosely sequestered calcium (Ca). The extent of degeneration and the distribution of Ca in a synergid varied among samples, and also between some sister synergids. However, there seemed to be no difference between sister synergids in the total amount of precipitates present in each cell. Characteristic signs of degeneration in the antimonatefixed synergids were: a gap above the filiform apparatus with fibrillar material, precipitates, and fusing or disintegrating membranes; increased precipitates in the nucleus, nucleolus, and endoplasmic reticulum; fusion or collapse of a few vacuoles in the chalazal core with precipitates and flocculent material deposited nearby. The numerous mitochondria and proplastids in the micropylar portion of the synergid remained intact and mostly free of precipitates. The shape and content of the chalazal vacuoles appeared to be disparate and dependent on the fixation procedure as well as the extent of degeneration within a synergid. The results suggest that the sister synergids of pearl millet undergo autonomous degeneration apparently in two independent sequences that may be spatially and temporally separated. The vacuoles appear to be dynamic organelles that store Ca in association with some other material. A high concentration of Ca may be localized along or between the common wall of the two filiform apparatuses.On specific Cooperative Agreement 58-6612-8-002 with the Department of Biochemistry, University of Georgia, Athens, GA 30602, USA     

Towards a species level tree of the globally diverse genus Chenopodium (Chenopodiaceae)

Chenopodium is a large and morphologically variable genus of annual and perennial herbs with an almost global distribution. All subgenera and most sections of Chenopodium were sampled along with other genera of Chenopodieae, Atripliceae and Axyrideae across the subfamily Chenopodioideae (Chenopodiaceae), totalling to 140 taxa. Using Maximum parsimony and Bayesian analyses of the non-coding trnL-F (cpDNA) and nuclear ITS regions, we provide a comprehensive picture of relationships of Chenopodium sensu lato. The genus as broadly classified is highly paraphyletic within Chenopodioideae, consisting of five major clades. Compared to previous studies, the tribe Dysphanieae with three genera Dysphania, Teloxys and Suckleya (comprising the aromatic species of Chenopodium s.l.) is now shown to form one of the early branches in the tree of Chenopodioideae. We further recognize the tribe Spinacieae to include Spinacia, several species of Chenopodium, and the genera Monolepis and Scleroblitum. The Chenopodium rubrum and the Ch. murale-clades were newly discovered as distinct major lineages but their relationships within Chenopodioideae will need further evaluation. Based on our results, we suggest the delimitation of Chenopodium to include Einadia and Rhagodia because these are part of the crown group composed of species of subg. Chenopodium that appear sister to the Atripliceae. The tetraploid crops such as Ch. berlandieri subsp. nuttalliae and Ch. quinoa also belong to Chenopodium sensu stricto. Trees derived from trnL-F and ITS were incongruent within this shallow crown group clade. Possible biological causes are discussed, including allopolyploidization.     

Polyspermy barriers in plants: from preventing to promoting fertilization

Barriers to polyspermy (fertilization of a female gamete by more than one sperm) are essential to successful reproduction in a wide range of organisms including mammals, echinoderms, fish, molluscs, and algae. In animals and fucoid algae, polyspermy results in early death of the zygote due to transmission of extra centrioles from the sperm and consequent disruptions to the mitotic spindle. Accordingly, a variety of mechanisms have evolved to prevent penetration of an egg by more than one sperm, or more than one sperm nucleus from fusing with an egg nucleus. The evolution of internal fertilization has also provided an opportunity to limit the number of sperm that gain access to each egg, as occurs in the mammalian female reproductive tract. Polyspermy and polyspermy barriers in plants have received much less attention. Plants lack centrioles and therefore, polyspermy would not be expected to cause lethal aberrant spindle organization. However, we find evidence from cytological, genetic and in vitro fertilization studies for polyspermy barriers in plants. Angiosperms, like mammals, are internally fertilized, and exert a high level of control over the number of sperm that have access to each female gamete. In particular, regulation of pollen tube growth ensures that in general only two sperm enter each embryo sac, where one fertilizes the egg and the other the central cell. Despite this 1:1 ratio of sperm to gametes within the embryo sac, angiosperms still require a mechanism to ensure that each female gamete is fertilized by one and only one sperm. Here, we present evidence suggesting that a polyspermy block on the egg may be part of the mechanism that promotes faithful double fertilization.     

《中国植物志》和《中国被子植物科属综论》所涉及"科"界定之比较

对采用A .Engler (1936 )被子植物分类系统的《中国植物志》和根据吴征镒等(2 0 0 2 )被子植物分类系统的《中国被子植物科属综论》中科的界定进行了比较。这不仅有助于掌握吴征镒等系统的观点 ,也有益于理解被子植物系统学中当前划分“科”的新趋向。     

中国高等植物省级分布新记录(四)

报道了十字花科、海桐花科、牛栓藤科、柽柳科、堇菜科、旌节花科、安息香科、报春花科、山矾科和百合科共12种1变种植物在我国10个省区的分布新记录。其中吉林分布新记录的有北萱草(HemerocallisesculentaKoidz.),山西分布新记录的有具鳞水柏枝(MyricariasquamosaDesv.)、维西堇菜(ViolamonbergiiW.Beck.)和海乳草(GlauxmaritimaLinn.),陕西分布新记录的有海金子(PittosporumillicioidesMak.)和蒙古堇菜(Violamon-golicaFranch.),甘肃分布新记录的有西域旌节花(StachyurushimalaicusHook.f.&Thoms.exBenth.),江西分布新记录的有缝线海桐(PittosporumperryanumGowda),河南分布新记录的有唐古拉碎米荠(CardaminetangutorumO.E.Schulz),湖北分布新记录的有黄牛奶树(Symplocoscochinchinensis(Lour.)S.Moorevar.laurina(Retz.)Nooteboom),湖南分布新记录的有大花野茉莉(StyraxgrandiflorusGriff.),贵州分布新记录的有少花海桐(Pit-tosporumpauciflorumHook.&Arn.),广西分布新记录的有红叶藤(Roureaminor(Gaerth.)Leenh.)。     

云南腾冲新近纪两种被子植物化石的角质层构造及其古环境意义

重点描述云南腾冲晚第三纪两种被子植物化石Betula mioluminifera Hu et Chaney,Carpinus subcordata Nathorst的角质层构造,并分析它们的现存最近亲缘种B.luminifera Winkler和C.cordata B1.var.mollis Cheng et Chen的表皮特征。实验分析证明：化石叶片的气孔参数可以推测地质历史时期大气CO2的浓度,并进而分析古环境的变化。C．subcordata Nathorst叶片能作为大气CO2浓度的生物指标。     

四川被子植物区系特征的初步研究

四川地区被子植物区系188科1493属8711种及1252变种,全球50％以上的科都有代表,与毗邻地区及世界植物区系有着广泛而密切的联系。区系古老而原始,珍稀孑遗类群丰富;单型或少种的科属众多,含100种以上的大科和大属也十分繁荣;含5种以下的属占76.89%,但占总属数约22.64%的多种属和大属是区系的主体,包含区系总种数的63.28%。科的分布类型有明显热带性质,属、种的分布类型反映出典型的亚热带属性。优势现象明显,特有类群和表征类群丰富。该地区被子植物区系对中国乃至东亚都有代表性。     

Application of ITS sequences of nuclear rDNA in phylogenetic and evolutionary studies of angiosperms

Nuclear rRNA genes (rDNA) in angiosperms are arranged in long tandem repeat ing units, much like those of other higher eukaryotes. Owing to rapid concerted evolution, the repeat units have homogenized or nearly so in most species. The internal transcribed spacer (ITS) of nuclear rDNA is composed of ITS1 and ITS2, which are seperated by 5.8S rDNA. The two spacers, ITS1 (187～298 bp) and ITS2 (187～252 bp), can be readily amplified by PCR and sequenced using universal primers. The sequences contain many vari able sites and potential informative sites among related species, and have been proven to be a useful molecular marker in phylogenetic and evolutionary studies of many angiosperm taxa. It can be used not only in classification and phylogenetic inferences at the levels of family, subfamily, tribe, genus and section, but also in reconstruction of reticulate evolution and de tection of the speciation via hybridization and polyploidization. But this region may not be useful for resolving phylogenetic relationships among families or taxa of higher hierarchy ow- ing to the rapid variation of the ITS sequences.