甘蓝型油菜（Brassica napus L.）花粉和柱头的发育及其与自交不亲和性的关系

作者用扫描电镜、透射电镜和组织化学方法研究了甘蓝型油菜(Brassica napus L．)花粉和柱头的发育及相互作用,得到了如下结果： 一．甘蓝型油菜具有典型的同型孢子体自交不亲和性(Homomorphic and sporophytic self-incompatibility)。自花授粉后，部分花粉粘住在乳突细胞表面，随后萌发出花粉管，花粉管生长受阻于乳突细胞，花粉管表现出各种异常形态，缠绕卷曲(Coiled pattern),顶端膨大成基足状(pad-Like swelling),花粉管二叉分枝（dichotomous branching Pollen tubes），花粉管相互连接(connections of pollen tubes），有的花粉粒还形成两个花粉管。 二．不同时期的乳突细胞的扫描电镜观察表明： 开花前6—7天 乳突细胞壁内陷，柱头中央有一沟槽; 开花前4—5天 乳突细胞被有孔的块状物覆盖; 开花前2—3天 覆盖物消失，壁表面只剩下波状纹或小凹; 开花前l - 2天 乳突细胞充分吸水膨胀，呈指状，排列疏松，细胞壁上有一些小颗粒。此时的乳突细胞已发育成熟。 三.不亲和授粉时，花粉和乳突细胞均有强烈的胼胝质荧光。 四.乳突细胞的组织化学特点：缺乏淀粉积累，细胞壁和细胞质中有过氧化物酶活性。 五.乳突细胞的超微结构特点：细胞壁分为三层，蜡质层、角质层和纤维素层。粗面内质网成群分布在细胞壁附近，并以及泡形式向细胞壁分泌物质。缺乏质体，细胞核位于乳突细胞基部，细胞中央为大液泡占据。 六.花粉的超微结构发育特点：单核花粉已发育出内壁和外壁，外壁内层不明显。细胞核位于中央。细胞质浓厚，缺乏层膜结构而积累大量淀粉粒的质体存在于细胞质中。其他细胞器不发达。两细胞花粉时期，花粉壁接受乌氏体转运的孢粉素和含油体转运的脂类物质。生殖细胞没有壁，悬浮在营养细胞的细胞质中。细胞核大，细胞质稀薄，只有一些嵴不明显的线粒体。营养细胞的核显著，细胞质浓厚，线粒体发达，质体内部的淀粉消失，转变成嗜饿小体。内质网短而粗，遍布于细胞质中，高尔基体缺乏。 七.绒毡层积极参与了花粉外壁的建成。首先，它通过分泌作用把物质（可能是蛋白质）转移到单核花粉的腔隙中或在它后期滚解后，由分布在二细胞花粉间的粗面内质网合成蛋白质，转移到花粉壁内。其次，绒毡层细胞的质体层膜形成许多造油小体，至二胞花粉时，造油小体进入壁的柱状层，参与花粉鞘形成。第三，绒毡层细胞形成许多乌氏体，花粉发育后期，乌氏体与花粉外壁接触，将孢粉素转移到花粉外壁上。

Ecballocystopsis dichotomus sp. nov. (Chlorococcales, Chlorophyceae) from China

Ecballocystopsis dichotomus sp. nov. is the third described species of Ecballocystopsis that grows on rock under water and epiphytically on the filaments of Cladophora and Mougeotia (green algae) collected in a small irrigation ditch in Chong-yang county, Hubei Province (East longitude 29 degrees 30', North latitude 114 degrees 10') and in Zhu-xi county, Hubei Province (East longitude 32 degrees 20', North latitude 109 degrees 45'). The new species differs from E. indica IYENGAR (1933) in having dichotomous branching and its smaller sized thallus; it differs from the second species, E. desikacharyi PRASAD (1985), in having looped filaments, dichotomous branching and smaller cells. Three patterns of cell divisions were observed in E. dichotomus sp. nov. (transverse, longitudinal and oblique). It may be that the new species is evolutionary a more advanced species based upon the structure of its thallus and the manner of spore formation. The systematic position of the genus, based on the comparative studies of the genus Ecballocystis BOHLIN with Cylindrocapsopsis IYENGAR, is discussed.

Genome-wide computational identification of microRNAs and their targets in the deep-branching eukaryote Giardia lamblia

Using a combined computational program. we identified 50 potential microRNAs (miRNAs) in Giardia lamblia. one of the most primitive unicellular eukaryotes. These miRNAs are unique to G. lamblia and no homologues have been found in other organisms; miRNAs.

Branching Ratios of alpha Decay for Nuclei near Deformed Shell Closures

The generalized liquid drop model (GLDM) is extended to the region around deformed shell closure (270)Hs by taking into account the excitation energy EI+ of the residual daughter nucleus and the centrifugal potential energy V-cen(r). The branching ratios of alpha decays from the ground state of a parent nucleus to the ground state 0(+) of its deformed daughter nucleus and to the first excited state 2(+) are calculated in the framework of the GLDM. The results support the proposal that a measurement of alpha spectroscopy is a feasible method to extract information on nuclear deformation of superheavy nuclei around the deformed nucleus (270)Hs.

Understanding the branching ratios of chi(c1) -> phi phi,omega omega,omega phi observed at BES-III

In this work, we discuss the contribution of the mesonic loops to the decay rates of chi(c1) -> phi phi, omega omega, which are suppressed by the helicity selection rules and chi(c1) -> phi omega, which is a double- Okubo- ZweigIizuka forbidden process. We find that the mesonic loop effects naturally explain the clear signals of chi(c1) -> phi phi, omega omega decay modes observed by the BES Collaboration. Moreover, we investigate the effects of the omega - phi mixing, which may result in the order of magnitude of the branching ratio BR(chi(c1) -> omega phi) being 10(-7). Thus, we are waiting for the accurate measurements of the BR(chi(c1) -> omega omega), BR(chi(c1) -> phi phi) and BR(chi(c1) -> omega phi) which may be very helpful for testing the long- distant contribution and the omega - phi mixing in chi(c1) -> phi phi, omega omega, omega phi decays.

Self-Assembly of Rod-Terminally Tethered Three-Armed Star-Shaped Coil Block Copolymer: Investigation of the Presence of the Branching in the Coil to the Self-Assembled Behavior

Self-assembled behavior of rod-terminally tethered three-armed star-shaped coil block copolymer melts was studied by applying self-consistent-field lattice techniques in three-dimensional (3D) space. Similar to rod-coil diblock copolymers, five morphologies were observed, i.e., lamellar, perforated lamellar, gyroidlike, cylindrical and sphericallike structures, while the distribution of the morphologies in the phase diagram was dramatically changed with respect to that Of rod-coil diblock copolymers.

MEASUREMENT AND CALCULATION OF SPONTANEOUS EMISSION BRANCHING RATIOS, RELATIVE OSCILLATOR-STRENGTHS, TRANSITION-PROBABILITIES AND LEVEL LIFETIMES FOR ATOMIC URANIUM

We propose a laser induced sensitized fluorescence spectrometry for measuring the spontaneous emission branching ratios o?the transitions from the ten levels 5f36d7s7p-7M7, 5f36d7s7p-7L6, 5f37s27p-5K6, 5f26d27s2 - 5L7, 5f46d7s - 7L6, (17,070cm-1)-5L6, 5f26d27s2-5K6, 6d7s7p-7L5, 5f36d7s7p-7K5 and 5f26d27s2-5I5 to the ground state of atomic uranium (UI) for the first time. Their relative oscillator strengths have been measured by means of hollow cathode discharge (HCD) emission spectrometry. The radiative...

MEASUREMENT OF SPONTANEOUS EMISSION BRANCHING RATIOS IN MO(I) TRANSITIONS BY LASER-INDUCED SENSITIZED FLUORESCENCE

I. TNTRODUCTIONThe emission spectroscopic method is usually used to measure spontaneous emission branching ratios. As emission spectra cannot be detected in atomic beams, the laser-induced fluorescence or ion detection method is often used. When the fluorescence method is used to measure branching ratios, it is usually necessary to detect

Early expressed genes showing a dichotomous developing pattern in the lancelet embryo

Lancelets (amphioxus), although showing the most similar anatomical features to vertebrates, never develop a vertebrate-like head but rather several structures specific to this animal. The lancelet anatomical specificity seems to be traceable to early developmental stages, such as the vertebrate dorsal and anterior-posterior determinations. The BMP and Wnt proteins play important roles in establishing the early basis of the dorsal structures and the head in vertebrates. The early behavior of BMP and Wnt may be also related to the specific body structures of lancelets. The expression patterns of a dpp-related gene, Bbbmp2/4, and two wnt-related genes, Bbwnt7 and Bbwnt8, have been studied in comparison with those of brachyury and Hnf-3 beta class genes The temporal expression patterns of these genes are similar to those of vertebrates; Bbbmp2/4 and Bbwnt8 are first expressed in the invaginating primitive gut and the equatorial region. respectively, at the initial gastrula stage. However, spatial expression pattern of Bbbmp2/4 differs significantly from the vertebrate cognates. It is expressed in the mid-dorsal inner layer of gastrulae and widely in the anterior region, in which vertebrates block BMP signaling, The present study suggests that the lancelet embryo may have two distinct developmental domains from the gastrula stage, the domains of which coincide later with the lateral diverticular and the somitocoelomic regions. The embryonic origin of the anterior-specific structures in lancelets corresponds to the anterior domain where Bbbmp2/4 is continuously expressed.