盐生植物角果碱蓬种子二型性对环境的适应策略

角果碱蓬(Suaeda corniculata)是藜科一年生盐生植物, 在我国分布于北方盐碱滩涂和盐碱荒漠地区。角果碱蓬具有棕色和黑色两种异型体种子(简称棕色和黑色种子)。对采自内蒙古鄂托克前旗盐渍化生境的角果碱蓬二型种子的形态、休眠和萌发特性开展对比研究, 测定了二型种子休眠和萌发行为对温度、光照和盐分(NaCl)的响应, 以揭示盐生植物异型种子对温带盐漠生境的适应对策。结果表明: (1)二型性种子在大小、种皮特性和结实比例方面有显著差异。与黑色种子相比, 棕色种子个体较大, 种皮透水性强。黑色种子与棕色种子的结实比例约为5.6 : 1。(2)新成熟的棕色种子的萌发对各温度梯度和光照条件不敏感, 萌发率较高(84%-100%); 而新成熟的黑色种子萌发率较低(8%-78%), 萌发对光照敏感。(3)黑色种子具有浅度生理休眠, 种皮划破、赤霉素处理和低温层积均可有效地提高种子的萌发率。(4)二型种子萌发对土壤盐分的胁迫具有不同的响应。与黑色种子相比, 棕色种子对盐分胁迫不敏感, 在较高的盐分浓度下仍有较高的萌发率, 低温层积处理能够降低黑色种子对盐胁迫的敏感性, 有效地提高种子的初始萌发率、萌发恢复率和最终萌发率。角果碱蓬二型种子不同的形态、休眠和萌发特性, 提高了该物种在高度异质性生境中的适合度, 对种群成功地适应温带盐漠环境具有重要的意义。     

异子蓬二型性种子的种皮结构及离子含量差异

异子蓬(Borszczowia aralocaspica)是中亚荒漠区系特有的一年生盐生植物,其种子具有二型性。通过检测异子蓬二型性种子中的生理生化物质以及观察种皮的结构,比较异子蓬二型性种子中营养物质、养分全量以及种皮结构的差异,结果表明:(1)异子蓬的棕色种子只有一层薄种皮,而黑色种子不但具有一层薄的内种皮还有一层坚硬致密的外种皮;(2)棕色种子的质量大、质量频数分布较为集中,并且吸水迅速,在吸水率较低时就能够大量萌发;(3)棕色种子的可溶性糖、可溶性蛋白质、全氮、全磷以及K+、Na+、K+/Na+和Mg2+/Na+都显著高于黑色种子。说明在繁殖子代、产生二型性种子时,异子蓬对棕色种子和黑色种子之间的繁殖投入存在着巨大的差异,这可能是导致异子蓬二型性种子产生差异性萌发机制的重要原因。     

不同生境盐地碱蓬出苗及幼苗抗盐性比较

研究了盐胁迫对不同生境盐地碱蓬出苗、幼苗生长、离子积累和荧光参数等的影响.盐地碱蓬种子具有二型性,即外种皮柔软而半透明的棕色种子和外种皮坚硬的黑色种子.两种生境盐地碱蓬棕色种子的出苗率均明显高于黑色种子.与黑色种子相比,潮间带生境盐地碱蓬棕色种子在高盐环境下的出苗速率和出苗率高于盐碱地生境盐地碱蓬.各处理盐分浓度下,潮间带生境盐地碱蓬叶片的最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率(ΦPSⅡ)和地上部分生物量均低于盐碱地生境盐地碱蓬.高盐浓度下,潮间带生境盐地碱蓬叶片Na+和Cl-含量低于盐碱地生境盐地碱蓬.这些特征可能是盐地碱蓬长期适应不同生境的结果.     

盐地碱蓬二型性种子及其幼苗对盐渍环境的适应性

研究了盐地碱蓬二型性种子中离子含量与刚萌发幼苗耐盐性之间的关系,以及盐分对砂培盐地碱蓬二型性种子的幼苗生长、离子含量及光合特性的影响.棕色种子中离子含量显著高于黑色种子.与对照相比,100和400 mmol/L NaCl对棕色种子幼苗伸长没有抑制作用,却显著抑制黑色种子幼苗的伸长.NaCl处理下棕色种子的幼苗地上部分干重和主茎一级分枝数比黑色种子幼苗高,但二型性种子的幼苗叶片中离子含量、叶绿素含量及光合放氧速率却没有明显差异.上述结果说明盐地碱蓬棕色种子较高的离子含量可能是棕色种子刚萌发幼苗耐盐性较强的重要原因.棕色种子幼苗较高的生物量可能与其较多的分枝数有关.二型种子的这些特征可能决定了其在群落建成中所起到的不同作用.     

盐分、变温和激素处理对盐生植物异子蓬异型性种子萌发及成苗的影响

利用培养皿种子萌发及土壤盆栽方法对新疆特有藜科1年生盐生植物异子蓬(Suaeda aralocaspica)在不同盐分(NaCl和Na2SO4)、变温(4～30℃)和激素(GA3)处理下的种子萌发及成苗行为进行了研究.结果表明:异子蓬2种种子在NaCl和Na2SO42种盐胁迫下的萌发和休眠特性表现出明显差异,其中黑色种子的萌发率比褐色种子低;黑色种子属于非深度生理休眠,可分别通过15/30℃变温处理、4℃低温层积30 d及用800mg·L-1赤霉素处理促进其萌发;盐处理及温度变化对褐色种子的出苗率和成苗率影响显著,对黑色种子则不明显,说明黑色种子萌发存在着持续性的缓萌机制,有利于其形成持久种子库,以上特性均显示出其对初春盐生环境的适应性.     

新疆干旱区植物藜的种子异型性及其萌发机理

新疆干旱区分布的植物藜(Chenopodium album)的种子有黑色和褐色两种类型。对藜的异型性种子从形态结构、不同环境因素及激素或化学物质对萌发的影响以及同工酶谱等方面进行了研究,并对其萌发及适应异质环境的机理进行了讨论。结果表明:(1)藜的异型性种子在形态结构、萌发休眠特性等方面都存在明显差异:黑色种子种皮厚且硬,休眠,萌发慢,萌发率低;褐色种子种皮薄而软,不休眠,萌发快且萌发率高;(2)黑色种子的休眠可通过切除胚根外缘种皮得以完全解除;(3)赤霉素、乙烯利对黑色种子的萌发无明显促进作用;KNO3可较显著促进黑色种子的萌发;协同使用乙烯利和KNO3时,可显著提高黑种子萌发率,完全打破休眠;(4)黑色种子和褐色种子的酯酶、过氧化物酶及过氧化氢酶同工酶谱带存在差异;(5)黑色种子的萌发需要光照,而褐色种子则对光不敏感;低温贮藏对二者的萌发均无显著影响,尽管黑色种子的萌发率有波动。研究结果初步显示黑色种子的休眠是内源(胚)和外源(种皮)因素共同所致。藜的种子异型性及其萌发机理的形成是其对新疆干旱区异质化环境的高度适应。     

毛叶山桐子种子休眠与萌发特性的研究

目的：探究毛叶山桐子种子(Idesia polycarpa Maxim. var. vestita Diels)的休眠类型和解除休眠的最适方法，为生产实践中的种苗繁育提供一种能有效解除毛叶山桐子种子休眠和提高萌发率的方法。方法：以成熟的毛叶山桐子种子为材料，研究种子的水分透性及温度、光照、去垢剂、后熟、层积和植物激素对种子休眠与萌发的影响。结果：(1)种子具有发育成熟的胚，种皮被有蜡质层但具有透水性；(2)在10～35℃和交替光照(12 h光照/12 h黑暗，光强度为144μmol·m^-2·s^-1)下萌发30 d，种子的萌发率低于30%，具有休眠特性；(3)种子在完全黑暗条件下几乎不萌发，是一种需光性种子；(4)4℃和10℃层积30 d显著地增加种子的萌发速率和萌发率，后熟90 d则对种子萌发没有影响；(5)GA3能部分解除种子的休眠和促进萌发，将萌发率提高至56.7%，氟啶酮则没有作用。结论：毛叶山桐子种子的休眠类型为非深度生理休眠，解除休眠和促进萌发的最适方法是将种子在4℃或者10℃中层积30 d，然后在25℃和交替光照中萌发。     

异子蓬二型种子的萌发与休眠特性及其生态适应

异子蓬为中亚荒漠的特有种,其果实为胞果,花被片在结果时宿存包被果实形成浆果状的散布单位.对异子蓬的散布单位、果实形态进行比较观察,并在5/15℃、5/25℃、15/25 ℃(暗/光=12h/12h)3个温变周期下进行种子萌发实验,结果表明:(1)异子蓬的散布单位绿色、浆果状,有大小两种形态;大小两种散布单位内包被的果实在形状、大小、颜色上存在着明显差异.(2)大的散布单位内包被的果实圆形,扁平,褐色,无光泽,直径(2.64±0.03) mm,重量(3.68±0.04) mg;小的散布单位内包被的果实双凸镜形,黑色,有光泽,直径(2.40±0.04) mm,重量(2.86±0.06) mg.(3)褐色种子在3个温变周期下的萌发率都在81%以上,萌发速度快,而黑色种子萌发率低,萌发慢,具有休眠现象.(4)划破种皮及低温层积处理可显著提高黑色种子在3个温变周期下的萌发率,延长储存时间也可有效地促进黑色种子的萌发,表明黑色种子处于非深度生理休眠状态.异子蓬产生的两种不同类型的种子及其在时间和空间上的萌发差异对荒漠异质环境具有重要的适应意义.     

胡杨种子萌发对温光条件和盐旱胁迫的响应特征

以胡杨(Populus euphratica)种子为材料,分别设置光照(连续光照、12h光照/12h黑暗、连续黑暗)温度(10/15℃、15/20℃、20/25℃、25/30℃、30/35℃和35/40℃)试验、PEG6000渗透胁迫(0、-0.1、-0.2、-0.4、-0.6、-0.8、-1.0、-1.2、-1.4和-1.6MPa)试验和NaCl胁迫(0、0.05、0.10、0.20、0.30、0.40、0.60和0.80mol/L)试验,考察室内种子萌发对温度、光照和盐旱胁迫的敏感性,揭示胡杨种子萌发阶段对生境资源的适应策略。结果显示:(1)胡杨种子在温度(10℃/15℃~35℃/40℃)与连续光照、连续黑暗和12h光照/12h黑暗组合处理条件下均能萌发,且最终种子萌发率均能达到77%以上;3种光照条件下,种子萌发的最适温度范围均为25℃/30℃~30℃/35℃,在该温度范围种子萌发表现出快速、集中的特点,且3种光照条件对种子萌发的影响无显著差异。(2)胡杨种子可以在-1.4~0 MPa渗透势溶液中萌发,而在-1.0~0 MPa间最终萌发率均达到90%以上,且相互之间无显著差异;但当渗透势低于-0.4 MPa时胡杨种子萌发进程和萌发速率受到显著影响,当溶液渗透势低于-1.2 MPa时种子萌发受到显著抑制。(3)胡杨种子可以在0~0.80mol/L NaCl溶液中萌发,而最终萌发率、萌发速率均随着NaCl溶液浓度的增高逐渐降低,但在0~0.20mol/L范围内无显著差异;当NaCl溶液浓度大于0.20mol/L时,种子最终萌发率、种子萌发进程和萌发速率均受到显著抑制,萌发高峰期逐渐向后推移。研究结果表明,胡杨种子萌发时温度比较宽泛,对光照无严格要求,适宜温度下萌发快速集中,且萌发时对盐旱胁迫具有一定程度的忍耐性。这些特性有助于胡杨种子充分利用有限的水分条件而快速完成萌发,是胡杨种子萌发对干旱荒漠地区干旱少雨环境的一种生态适应策略。     

NaCl胁迫对2种表型盐地碱蓬种子萌发的渗透效应和离子效应研究

采用高低2个浓度的NaCl、LiCl及等渗甘露醇溶液处理紫红色表型(紫色型)和绿色表型(绿色型)盐地碱蓬种子,通过测定它们的种子萌发率、吸胀速率和胚内离子含量,研究NaCl胁迫对2种表型种子萌发的离子效应和渗透效应.结果表明:(1)2种表型盐地碱蓬种子萌发率在高浓度(300 mmol/L)和低浓度(100 mmol/L)NaCl处理下均显著降低,紫色型种子萌发率在低浓度下显著低于绿色型,而在高浓度下却显著高于绿色型;绿色型种子萌发率在高浓度(30 mmol/L)和低浓度(10 mmol/L)LiCl处理下均未受到显著影响,但紫色型种子萌发率却均极显著降低;2种表型盐地碱蓬种子萌发率在低浓度等渗甘露醇处理下均极显著低于低浓度NaCl处理,而高浓度等渗甘露醇处理却均与高浓度NaCl处理无显著差异.(2)2表型种盐地碱蓬种子的吸胀速率在低浓度NaCl处理下没有受到显著影响,但高浓度NaCl处理及与之等渗的高浓度甘露醇处理下都显著降低,而且紫色型种子的吸胀速率在等渗甘露醇处理时显著高于绿色型.(3)2种表型盐地碱蓬种子胚中的Na 含量和Na /K 在对照和低浓度NaCl处理下无显著差异,但紫色型种子胚中的Na 、K 含量在高浓度NaCl处理时都显著高于对照,且K 含量增加的幅度远大于Na 含量,导致紫色型种子胚中的Na /K 显著低于绿色型.研究发现,盐地碱蓬种子萌发在低浓度NaCl胁迫下主要受离子效应抑制,而高浓度NaCl胁迫下则主要受渗透效应抑制,紫色型种子萌发率在高浓度NaCl胁迫下高于绿色型的原因之一是前者能维持更低的Na /K 比.     

Systematic significance of mature embryo of bamboos

The mature embryo of seven species belonging to five genera of Indian bamboos is described. In all these the basic pattern of embryo organisation is same: the scutellar and coleoptilar bundles are not separated by an internode, the epiblast is absent, the lower portion of the scutellum and the coleorhiza are separated by a cleft and the margins of embryonic leaves overlap. The features unique to fleshy fruited bamboos are: presence of a massive scutellum, the juxtaposition of plumule and radicle and the occurrence of a bud in the axil of the coleoptile. The fleshy fruit bearing bamboos should be classified into one group, the tribeMelocanneae. Evidence is provided to recognise additional groups in the subfamilyBambusoideae.     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Phylogeny of cardinalfishes (Teleostei: Gobiiformes: Apogonidae) and the evolution of visceral bioluminescence

The cardinalfishes (Apogonidae) are a diverse clade of small, mostly reef-dwelling fishes, for which a variety of morphological data have not yielded a consistent phylogeny. We use DNA sequence to hypothesize phylogenetic relationships within Apogonidae and among apogonids and other acanthomorph families, to examine patterns of evolution including the distribution of a visceral bioluminescence system. In conformance with previous studies, Apogonidae is placed in a clade with Pempheridae, Kurtidae, Leiognathidae, and Gobioidei. The apogonid genus Pseudamia is recovered outside the remainder of the family, not as sister to the superficially similar genus Gymnapogon. Species sampled from the Caribbean and Western Atlantic (Phaeoptyx, Astrapogon, and some Apogon species) form a clade, as do the larger-bodied Glossamia and Cheilodipterus. Incidence of visceral bioluminescence is found scattered throughout the phylogeny, independently for each group in which it is present. Examination of the fine structure of the visceral bioluminescence system through histology shows that light organs exhibit a range of morphologies, with some composed of complex masses of tubules (Siphamia, Pempheris, Parapriacanthus) and others lacking tubules but containing chambers formed by folds of the visceral epithelium (Acropoma, Archamia, Jaydia, and Rhabdamia). Light organs in Siphamia, Acropoma, Pempheris and Parapriacanthus are distinct from but connected to the gut; those in Archamia, Jaydia, and Rhabdamia are simply portions of the intestinal tract, and are little differentiated from the surrounding tissues. The presence or absence of symbiotic luminescent bacteria does not correlate with light organ structure; the tubular light organs of Siphamia and chambered tubes of Acropoma house bacteria, those in Pempheridae and the other Apogonidae do not.     

Host plants of someRhinanthoideae (Scrophulariaceae) of eastern North America

Twenty three species in 11 genera were examined in the field to determine hosts. OnlyStriga asiatica andSeymeria cassioides have a narrow host range being restricted to grasses and pines, respectively. These are the only species which cause pronounced and sometimes serious host damage. The other species attach to a great diversity of hosts.     

Apoptotic Regulation of Caspase Activity

Intracellular cysteine aspartate-specific proteases (caspases) play both signaling and effector roles in realizing the program of cell death. Caspases function as proteolytic cascades unique for each cell type and signal triggering apoptosis. All parts of the proteolytic cascades are duplicated and controlled by feedback signals. Amplification cycles between pairs of caspases (the third and the sixth, the ninth and the third, the twelfth and the sixth, and others) help multiply the initial apoptotic signal. The presence of physiological inhibitors of apoptosis that directly interact with caspases creates a multilevel regulatory network of apoptosis in cell. The caspase proteolytic cascades are also regulated by sphingolipid secondary messengers, among them ceramide, sphingosine, and their phosphates. Moreover, an association of the caspase signaling with ubiquitin-dependent proteolysis is shown in cells. In particular, the use of extracellular activators and inhibitors of caspases allows irreversible activation of apoptosis in tumor cells or the prevention of apoptosis in cortical neurons under neurodegenerative diseases.     

Analysis of twin of eyeless regulation during early embryogenesis in Drosophila melanogaster

The Drosophila Pax6 homolog twin of eyeless (toy) is so far the first zygotically expressed gene involved in eye morphogenesis in Drosophila. The study of its expression during embryogenesis is therefore informative of the initial events of eye development in Drosophila. We have analyzed how the initial expression domain of toy at cellular blastoderm is regulated. We show that the three maternal patterning systems active in the cephalic region (the anterior, terminal and dorsal-ventral systems) cooperate with zygotically activated gap genes to shape the initial expression domain of toy. Whereas Bicoid, Dorsal and Torso signaling synergistically act as activators, Hunchback, Knirps and Decapentaplegic act as repressors.     

A molecular phylogeny of Hebeloma species from Europe

In order to widen the scope of existing phylogenies of the ectomycorrhizal agaric genus Hebeloma a total of 53 new rDNA ITS sequences from that genus was generated, augmented by sequences retrieved from GenBank, and analysed using Bayesian, strict consensus and neighbour joining methods. The lignicolous Hebelomina neerlandica, Gymnopilus penetrans, and two species of Galerina served as outgroup taxa. Anamika indica, as well as representatives of the genera Hymenogaster and Naucoria, were included to test the monophyly of Hebeloma, which is confirmed by the results. Hebeloma, Naucoria, Hymenogaster and Anamika indica cluster in a strongly supported monophyletic hebelomatoid clade. All trees largely reflect the current infrageneric classification within Hebeloma, and divide the genus into mostly well-supported monophyletic groups surrounding H. crustuliniforme, H. velutipes, H. sacchariolens, H. sinapizans, and H. radicosum, with H. sarcophyllum being shown at an independent position; however this is not well supported. The section Indusiata divides with strong support into three groups, the position of the pleurocystidiate Hebeloma cistophilum suggests the possible existence of a third subsection within sect. Indusiata. Subsection Sacchariolentia is raised to the rank of section.     

New species of Peruvian Orchidaceae III

Sixteen new species are proposed in the generaAckermania, Dressleria, Epidendrum, Maxillaria, Oncidium, Rodriguezia, Sigmatostalix, andTrigonidium. All new species are illustrated.Maxillaria vittariifolia L. O. Williams is newly recorded for Peru. A key is provided forTrigonidium of Peru.Trigonidium loretoense Schltr. andT. peruvianum Schltr. are lectotypified.     

Interaction of Synthetic Analogues of Natural Chalcones and Flavones with Guanidine

The reaction of chalcones and flavones with guanidine in ethanol results in 2-(2-aminopyrimidinyl-4)-phenols.