Stock Identification of Gag, Mycteroperca microlepis, Along the Southeast Coast of the United States

The gag grouper Mycteroperca microlepis is an important component of commercial and recreational fisheries along the South Atlantic coast of the United States and in the Gulf of Mexico. Over the past two decades, this species has experienced significant declines in abundance and an increasing skew in sex ratios. Analysis of microsatellite DNA variation in this species shows mosaic patterns of population subdivision and significant departures from Hardy-Weinberg equilibrium in all sampling locations. Given the length of the pelagic stage (egg and larvae), the prevailing current patterns, and the migratory capabilities of the adults, it is unlikely that these observations are the result of restricted gene flow among genetically differentiated populations. The apparent structure of gag populations most likely reflects inbreeding in size-limited populations. Population declines, skewed sex ratios, and perhaps variance in female fecundity appear to have acted in concert to limited the number of individuals that contribute to a given year class. These data are reinforced by studies of other fish stocks that have experienced precipitous declines over the past two decades. Received April 13, 1998; accepted September 30, 1998.     

Active female courtship behavior and male nutritional contribution to female fecundity in Bruchidius dorsalis (Fahraeus) (Coleoptera: Bruchidae)

Mating behavior and the male's contribution to female fecundity were studied in the bean weevil Bruchidius dorsalis (Fahraeus) (Coleoptera: Bruchidae) in comparison with two other species, Callosobruchus chinensis (which infests stored beans) and Kytorhinus sharpianus (which feeds on wild legumes). Only females of B. dorsalis showed multiple mating and characteristic precopulatory behavior that appeared to solicit the male's nutritious secretion. In contrast, all females of the other two species did not copulate multiply and did not show such precopulatory behavior. In B. dorsalis, the decrement of male body weight just after copulation indicated that seminal fluid weighing as much as approximately 7% of the male's body weight was transferred to the female. Fecundity was more than eight times higher in females that had copulated ten times than in females that had copulated only once, indicating that males paid most of the nutritional cost of egg production. These facts suggest that the sex role is reversed in B. dorsalis. Received: May 22, 1998 / Accepted: July 19, 1999     

Abnormality in Male Organ Development and Fertility of Photoperiod sensitive Genic Male Sterile Rice Plants Under Short Day Condition

Ten photoperiod-sensitive genic male sterile rice (PGMSR) lines were studied to observe the development of male organs of their short day (SD) plants. The results were shown as follows: 1 ) The self seed-setting rate and the percentage of fertile pollen of these PGMSR lines were much lower than those of the controls. 2) All the male sterile line plants had variant barriers in anther dehiscing and pollen scattering. In addition, some of their stigmas were devoid of pollen, and some self pollen grains on their stignas germinated weakly. 3) Female fertility of those plants was believed to be normal through observation in their embryo sac development and cross seed-setting rate. The authors deduced that the male sterile gene expression becomes the major factor for low rate of self seed-setting of PGMSR plants under SD condition.     

Studies on the Development of Gametophytes in Cornus officinalis (Cornaceae)

The floral bud of Cornus officinalis Sieb. et Zucc. began to differentiate at the end of April. In the beginning of November, female and male gametophytes reached their maturation. The flowers fell off in the following March. The wall of the microsporangium comprised epidermis, endothecium, two or three middle layers and a single layer of amoeboid tapetum with two nuclei. The extra-tapetal membrane was formed during the later stage of the development of anther. Meiosis of microspore mother-cell was normal and cytokinesis was of the simultaneous type. The tetrad was tetrahedral in shape. The mature pollen grains were 2-celled and 3-colporate. The ovule was unitegminous and tenuinucellate. During the development of the ovule, some special structures were formed, e. g. hypostase and obturator which originated from the integument. A single archesporium differentiated immediately below the nucellar epidermis. It functioned directly as the megaspore mother-celL This cell under went meiosis to form a linear tetrad. The chalazal megaspore was functional. The development of the embryo sac was conformed as the polygonum type. Two polar nuclei fused into the secondary nucleus and 'three antipodal cells degenerated soon after the embryo sac reached its maturation, at that time the female gametophyte had become an embryo sac which consisted of only four cells each with a nucleus just before two months of blooming. The nuclei of some synergids located in the chalazal part of the cells. Contrarily, the micropylar past of the synergids were occupied by a large vacuole. The secondary nucleus was usually located in the chalazal part of the embryo sac.     

Effects of Introducing the Chimaeric Gene TA29 Barnase on the Tapetum and Pollen Development in Tobacco

The development of tapetum and pollen in transgenic tobacco (Nicotiana tabacum L. ) harboring a chimaeric gene TA29-Barnase was compared with that of the wild-type plant. The specific expression of the exogenous genes in anther led to premature tapetal degradation, which started at the early stage of meiosis and terminated at the tetrad stage. In the wild-type anthers, tapetal degradation started at the early stage of bicellular microgametophyte and ended at the later stage of pollen development. The cytological changes of tapetal degradation in the transgenic plants were characterized by vacuolization of the tapetal cells, then nuclear condensation, and consequent massive degradation of tapetal cells. Meanwhile, the pollen mother cells gradually degraded and became destroyed along with the progress of meiosis, leaving only a few which could successfully complete their meiosis to form microspores. This observation also indicated that the TA29-Barnase gene in anther was not uniformly expressed. In addition, the structural difference between the male sterility induced by exogenous gene and the natural sterile was also discussed.     

Studies on Nucleic Acid and Protein Synthesis and D evelopment of Male Gametnphyte of Clivia nobilis Cultured in Vitro

A simple method for culture male gametophyte (MG) of Clivia nobilis in vitro was established and the process of their development was observed. After research on dynamic of nucleic acid and protein synthesis of MG in various developmental stages by using of inhibitors and autoradiography authors found that DNA synthesis fro mrelease of tetrad to sperm only takes place in nucleus of interphase. There is no 3H-tymidine incorporation into vegetative nucleus (Vn), generative nucleus (Gn) or nucleus of sperm in 96 hours before dehiscence of anthers (BDA). The dynamic of protein synthesis is similar to the same of RNA’s. Both of them have three peaks and two intermissions. The 1st peak is in 12–9 days BDA. The 2nd is in 7–5 days BDA and intermitted from 48 hours BDA. The 3rd begins from the 1st hour after culture (AC) decleases at 6th hour AC and stops before 20th hour AC. The kind of inhibitor, the time and quanlity of treatment are affected the morphogenesis, showing the relationship to synthesis among DNA, RNA and protein and to the same between biomacromolecular and morphological development of MG.     

小地老虎雄蛾中胚层生殖腺缢缩瓣膜结构和功能

该文通过光镜、电镜和生化分析等方法,详细观察了小地老虎雄蛾中胚层生殖腺缢缩的形态、数目、位置和细胞特化的瓣膜结构,并研究了缢缩的瓣膜结构和隔离中胚层生殖腺分泌物的功能。结果表明：缢缩是雄蛾中胚层生殖腺上显著收缩段,有7个,分别在雄性附腺—贮精囊、贮精囊—精包腺1段、精包腺1～5各段之间,精包腺5段—C形管;缢缩自内向外为4层,即瓣膜细胞、底膜、肌肉和围膜,肌肉层发达;缢缩瓣膜结构是细胞极度伸长特化形成的,其特点是：多数细胞伸长超过原长度的一倍以上,顶区膨大呈蘑菇突,纵横交错堵塞管腔,其顶段的微绒毛致密而细长,稠密的粗面内质网和稀疏的高尔基体环绕在核的四周,细胞间隙发达;缢缩瓣膜结构具有隔离相邻区段中胚层生殖腺分泌物的功能,致使各区段分泌物在蛋白质电泳谱带数和迁移率,以及经PAS染色后在腺腔横切面上的构象存在显著差异。     

Studies on Photoperiod-sensitive Genic Malesterile Rice in Terms of Developmental Biology

Investigations on the mechanism of fertility alternation and its regulation in photoperiodsensitive genic male-sterile rice (PGMR) have received considerable attention due to the important significance in both basic research of plant developmental biology and PGMR potential value in the development of two line hybrid rice seed programs. The present review described the major achivements of study on PGMR in terms of developmental biology: phytochrome was found to be the photoreceptor involved in photoperiod-modulated fertility alternation in PGMR; chloroplasts played a significant role in the photoperiodic signal transduction; gibberellins and auxin might be the chemical signals for fertility regulation; identifying of special proteins promoted the exploration of specially expressed genes related to fertility regulation in PGMR. The author hypothesized that four main steps of photoperiodic signal transduction were involved in the realization of male sterility-multistage magni-fied injury effects to normal function of PGMR induced by long-day stress. There was defect in the anther development of PGMR, and the resistance of anthers to environmental stress was weakened. The multifactor coaction model for photoperiod regulation in fertility alternation in PGMR was proposed and discussed.     

黄瓜茎端ABA/GA_4比值与花芽性别分化的关系(英文)

在同一环境条件下,单雌性株茎端ABA含量显著高于雌雄同株的,而GA_4水平却正好相反。 较高的ABA/GA_4比值有利于黄瓜雌性分化,反之则有利于雄性分化。促进黄瓜雄性分化的生长物质GA_3和AgNO_3会引起黄瓜茎端ABA/GA_4比值的下降,而促进其雌性分化的生长物质乙烯利(Ethrel)则会引起ABA/GA_4比值的上升。     

Ultrastructure of the labellar epidermis in selected Maxillaria species (Orchidaceae)

The ultrastructure of the labellar epidermis of 13 species of Maxillaria and one hybrid was examined using low-vacuum scanning electron microscopy (SEM). The labellum may be homogeneous and glabrous or papillose, comprising one type of cell only, or heterogeneous with papillae, uniseriate trichomes and/or glands in various combinations. The trichomes are unbranched and multicellular with pointed or truncated tips. Moreover, in some taxa, moniliform trichomes occur, and these are thought to fragment with the formation of pseudopollen. Homogeneous and heterogeneous labellar organization may represent separate evolutionary lines. Preliminary results suggest that labellar features may provide additional taxonomic characters allowing determination of intrageneric affinities.