In vitro attempts to overcome the cross-incompatibility between Vaccinium corymbosum L. and V. elliottii Chapm.

Summary Seed was readily obtained from V. corymbosum zygotes using embryo rescue techniques, even when embryos were cultured at proembryonic stages. Best in vitro seed development was obtained when ovules were cultured attached to placental tissues. Successful fruit and seed development in culture occurred only when the fruit was cut longitudinally or when the basal portion of the fruit was removed previous to plating. Addition of various vitamins, amino acids, and growth regulators to the nutrient medium did not increase seed production. Attempts to rescue hybrid embryos from V. croymbosum (tetraploid) x V. elliottii (diploid) crosses by in ovulo and in ovary culture gave a few presumably hybrid seed, but at a rate no greater than when normal crossing procedures are used.Florida Agricultural Experiment Station Journal Series No. 5748     

The Effects of Inflorescence Size and Flower Position on Biomass and Temporal Sex Allocation in <Emphasis Type="Italic">Lobelia sessiliflora</Emphasis>

To test the prediction of sex allocation theory that plants or flowers high in resource status emphasize the female function, we explored the variation in both biomass (the number of pollen grains and ovules) and temporal (male and female durations) sex allocation among and within plants of protandrous Lobelia sessilifolia in relation to plant size and flower position within plants. Among plants, the mean number of pollen grains and ovules per flower of a plant increased with plant size, whereas the mean P/O ratio (number of pollen grains/number of ovules ratio) decreased with plant size. The mean male duration, the mean female duration, and the mean ratio of male duration/flower longevity per flower of a plant were not correlated with plant size. Thus, large plants emphasized female function in terms of biomass sex allocation, which is consistent with the prediction of size-dependent sex allocation theory. The results for temporal sex allocation, however were inconsistent with the theory. Within plants, the mean number of pollen grains and ovules per flower at each position decreased from lower to upper flowers (early to late blooming flowers) and that of the P/O ratio increased from lower to upper flowers. The mean male duration and the mean female duration per flower decreased from lower to upper flowers, whereas the mean ratio of male duration/flower longevity increased from lower to upper flowers. The population sex ratio changed from male-biased to female-biased. Thus, later blooming flowers emphasized the male function in terms of both biomass and temporal sex allocation, consistent with the sex allocation theory, regarding the change in the population sex ratio.     

Empirical assessment of the reproductive fitness components of the hybrid pine Pinus densata on the Tibetan Plateau

Pinus densata is distributed on the Tibetan Plateau, where it forms extensive forests at high elevations. Genetic studies have provided evidence that P. densata originated through hybridization between P. yunnanensis and P. tabuliformis. To clarify the relationships among these pines, and assess their reproductive fitness in their respective habitats, we conducted a comparative analysis of eight cone and seed morphometric traits and six reproductive traits in them. Among the eight morphometric traits examined, six appeared to be intermediate in P. densata between those of P. yunnanensis and P. tabuliformis. There were significant differences among the three pines in all of the morphometric traits, and P. densata showed greater variability in these traits than the other two pines. In contrast to the morphometric traits, the reproductive traits (including the proportions of filled and empty seeds, ovule abortion rate, seed efficiency, meiotic abnormalities during microsporogenesis and pollen viability) differed little among the three pines, indicating that they have similar overall rates of effective pollination and fertilization in their respective natural environments. Despite their location on the high plateau, natural populations of P. densata appeared to have normal levels of reproductive success, comparable to those of the two parental species in their natural habitats. This study provides empirical data characterizing the reproductive success and adaptation of a stabilized homoploid hybrid in a novel habitat that is ecologically and spatially inaccessible to its parental species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Development of Ovules and Embryo sacs in Ostrya virginiana (Betulaceae) and Its Systematic Significance

The development of ovules and embryo sacs in Ostrya virginiana was studied for the first time. Most ovaries had two ovules which were anatropous, unitegmic and crassinucellate. The ovule usually possessed several archesporial ceils which divided periclinally into the upper parietal cell and the lower sporogenous cell. The sporogenous cell functioned directly as megaspore mother cell. The tetrad of megaspores was linear in arrangement, and every megaspore might be functional. One ovule often contained 2- 6 embryo sacs and the embryo sac belongs to Polygonum type. It can be concluded from the present data that all ovules among the genera of the Betulaceae are unitegrnic. There are more groups with the phenomenon of multiple embryo sacs in anemophic plants such as Betulaceae, Casuarinaceae, Graminae, Jnglandaceae, Myricaceae, Simaroubaceae, Ulmaceae, than in entomophilous plants. Multiple embryo sacs also occur among some parasitic plants and saprophytes, e.g. Orobanchaceae, Cassytha in Lauraceae, Cuscuta in Convolvulaceae and Utricularia in Lentibulariaceae. It may be inferred that the characteristic of multiple embryo sacs be an evolutionary adaptation of those plants with lower pollination rate to increase the rate of fertilization. Finally, a comparison of embryological characters among the genera of the Betulaceae shows that the family is of a number of common embryological characters, such as multicellular archesporium, multiple embryo sacs in one ovule, and a long interval between pollination and fertilization. The diversity and systematic significance of several embryological characters among the “higher” hamamelid families are also discussed. It is still hard to explain the phy-logenetic relationships among those families clearly only with.     

The Ultracytochemical Localization of ATPase Activity in the Ovules of Sunflower

The ultracytochemical localization of ATPase activity was determined employing the method of lead precipitation in the ovules of sunflower (Helianthus annuus L.). No ATPase activity is observed in the egg and synergids except some at the filiform apparatus. Much ATPase activity is localized on the plasma membrane and wall of the central cell. In the antipodal cells, ATPase activity is also found on the plasma membranes, but only a little in their walls. In the integumentary tapetum, besides the plasma membranes, most of the nuclei are rich in ATPase. Between the integumentary tapetum and uncontinuous cuticle surrounding the embryo sac, there is a gap where a lot of ATPase are found. These ATPases are continuously linked with those in the central cell wall throuth the intervals of the cuticle. At the sites of the wall ingrowths of the central celT, abundant vesicles and other structures with high ATPase activity aggregate noticeably in the gap region. According to the ATPase distribution in the ovules, we propose that the whole surface of embryo sac functions in absorbing nutrients directly from the apoplast outside the cuticle, especially via the wall-membrane apparatus of 'he central cell.     

Regulation of In Vitro Parthenogenesis and Somatic Proliferation in Sunflower by Several Factors

Culture of unfertilized ovules in sunflower (Helianthus annuus L.) could be induced to form parthenogenetic embryoids, endothelial embryoids and integumentary calli. Various factors exerted regulatory influences on the production of these structures. The key factors were exogenous hormone, sucrose concentration and cold-pretreatment. In hormone-free condition, parthenogenesis was promoted without any occurence of somatic embryoids or calli. Addition of exogenous hormone MCPA induced proliferation of sporophytic tissue and meanwhile, reduced the induction frequency of parthenogenesis. Relatively high sucrose level favored the Froduction of parthenogenetic embryoids. Reducing sucrose concentration favored the integumentary calli. The optimal sucrose concentration for endothelial embryoids was intermediate between them. Cold-pretreatment also played an effective role in promoting parthenogenesis and inhibiting integumentary calli. By combining these three factors, we were able to. work out a culture technique which significantly enhanced the inductionfrequency and growth. of parthenogenetic embryoids and completely eliminated somatic embryoids and calli.     

Production of Virus-tree Nucellar Plantlets from Unfertilized Ovules of Citrus in vitro

On a series of Murashige and Tucker (MT) media supplemented with different growth regulators, the 8-week-old unfertilized ovules of Washington navel orange (Citrus sinensis) were able to regenerate perfect plantlets via somatic embryogenesis or organogenesis. The sorts and combinations of exogenous hormones had remarkable effects on the induction, growth and differentiation of its callus. It was found that the most suitable induction medium was MT medium supplemented with 1.0 mg/l BA and 0.5mg/l 1AA. The most suitable differentiation medium was MT medium supplemented with 1.0 mg/l IBA. It was proved by indicator plant examination that the nucellar plantlets free of citrus exocortis virus (CEV) and citrus tristeza virus (CTV) had been obtained from infected trees.     

The Studies on Embryology in Fritillaria ussuriensis Maxim

The development of the anther wall follows Basic-type. The cytokinesis at the time of pollen mother cell meiosis conforms to successive type. The arrangement of the microspores in the tetrad is referred to isobilateral. The primary wall between the generative cell and the vegetative cell is callose. The callose wall is easily detected under the fluorescence microscope. The mature pollen grain is 2-celled type. The ovule is bitegminous, tenui-nucellar and anatropous. The development of the female gametophyte follows Fritillaria-type. The mature embryo sac. consists of the six cells including the seven nuclei. The fertilization is referred to the premitotic syngamy type. The fusion of the female and male nucleoli is not observed at the end of the fertilization. The division of the primary endosperm nucleus is earlier than that of the zygote. The development of the endosperm is referred to nuclear type. The division of the zygote is transverse of longitudinal, the development of the embryo conforms to Onagradtype. When the seed is mature, the embryo is at the proembryo stage without differentiation and the endosperm cells are not absorbed.     

低温对蝴蝶兰胚珠发育的影响

低温(12-18℃)处理的蝴蝶兰,授粉50 d开始分化胚珠原基、60 d胚囊处于大孢子母细胞时期,比常温(20-25℃)下的推迟10-15 d;授粉70 d,常温下的蝴蝶兰植株已完成雌配子体发育和双受精,而低温处理的蝴蝶兰仍未完成大孢子的发生过程.低温处理的蝴蝶兰,胚囊发育过程中珠心细胞提前退化,在大孢子母细胞外围形成较厚的胚囊壁.胚囊只发育到单核胚囊阶段,没有形成成熟胚囊.     

Embryo sac development is affected in Petunia inflata plants transformed with an antisense gene encoding the extracellular domain of receptor kinase PRK1

 In a previous study of the function of a pollen-expressed receptor kinase of Petunia inflata, PRK1, it was found that transgenic plants carrying an antisense-PRK1 gene were unable to transmit the transgene through either the male or, unexpectedly, the female. In this report, the nature of this female phenotype was studied using one of the transgenic plants, ASRK-13. Electron and light microscopic examination of the embryo sac and seed development of ASRK-13 and a wild-type plant revealed that embryo sac development of approximately half of the ovules of ASRK-13 was abnormal. The development of the affected embryo sacs was arrested at the late stages of megagametogenesis. The majority of the affected embryo sacs completed three rounds of mitosis normally, but failed to progress through the maturation stages when cell expansion, nuclear migration, and differentiation take place. The remaining small number of abnormal embryo sacs were arrested at either the four- or eight-nucleate stages. The ovules containing the defective embryo sacs apparently failed to be fertilized, resulting in degeneration of half of the seeds produced by ASRK-13. RNA gel blot analysis suggests that the PRK1 gene is expressed in the ovary, albeit at a much lower level than in the anther. The possibility that the antisense PRK1 gene is responsible for the abnormal embryo sac development is discussed. Received: 25 April 1997 / Revision accepted: 25 June 1997