Research on Pollen Grains of Tetraploid Lines and Diploid Control Line of Chrysanthemum cinerariifolium (Trev.) Vis.

[Objective] The aim was to study characters of pollen grains of tetraploid lines and diploid control line of Chrysanthemum cinerariifolium (Trev.) Vis.,morphological characters,fertility of pollen grain and germination percentage of seeds. [Method] Pollen grains were prepared by sulphuric acid-acetyl oxide decomposition method. The lengths of polar axis and equatorial axis of pollen grains were determined with general optical microscope. The morphology of pollen grains was observed with SEM (scanning electron microscope) and the typical visual fields of 2 500× (or 2 000×),7 000× were taken pictures. [Result] Comparing with the diploid control line,the pollen grains of five tetraploid lines which were tested were different from the diploid line in morphology,sculpture,etc.. 4 of the 5 tested samples were significant larger than the diploid line in size and one was similar to the diploid line. [Conclusion] This research provided references for breeding tetraploid improved varieties of Chrysanthemum cinerariifolium (Trev.) Vis. with good fertility and high germination percentage.

Airborne Pollen Grains Of Afyon, Turkey

The airborne pollen grains of Afyon have been studied for a two_year period (1999-2000) with a Durham sampler. A total of 14 367 pollen grains belonging to 40 taxa have been identified and recorded with some unidentified ones. Of them, 6 732 were identified in 1999 and 7 635 in 2000. Of the total pollen grains, 69.67% were arboreal, 26.64% non_arboreal and 3.68 % unidentified. The majority of the investigated pollen grains were from Pinus, Gramineae, Cupressaceae, Platanus , Chenopodiaceae/Amaranthaceae, Quercus, Ailanthus, Moraceae, Juglans , Salix, Cedrus and Rosaceae. The highest level of pollen grains was in May.

Plant Pollen Grains:A Move Towards Green Drug and Vaccine Delivery Systems

Pollen grains and plant spores have emerged as innovative biomaterials for various applications such as drug/vaccine delivery,catalyst support,and the removal of heavy metals.The natural microcapsules comprising spore shells and pollen grain are designed for protecting the genetic materials of plants from exterior impairments.Two layers make up the shell,the outer layer(exine)that comprised largely of sporopollenin,and the inner layer(intine)that built chiefly of cellulose.These microcapsule shells,namely hollow sporopollenin exine capsules have some salient features such as homogeneity in size,non-toxic nature,resilience to both alkalis and acids,and the potential to withstand at elevated temperatures;they have displayed promising potential for the microencapsulation and the controlled drug delivery/release.The important attribute of mucoadhesion to intestinal tissues can prolong the interaction of sporopollenin with the intestinal mucosa directing to an augmented effectiveness of nutraceutical or drug delivery.Here,current trends and prospects related to the application of plant pollen grains for the delivery of vaccines and drugs and vaccine are discussed.

Scanning Electron Microscope Observation of Three Species on Pollen Grain Morphology and Leaf Epiderm Shape in Gramineae Triticeae

The pollen grain morphology and leaf epiderm shape and microstructural of Rye（ Secale cereal ）, common wheat and Octoploid Trititrigia were observed with the scanning electron microscope（SEM）. The results revealed that there were great differences between pollen and leaf epiderm microcosmic morphology in three species. Such characteristics of Octoploid tnticalwere between those of common wheat and Rye. The morphology of pollen grain and leaf epiderm shape counld be used as an index for taxonomy for genera and species, and had somewhat scientif- ic references to identify new multiploid species created by chromosome engineering.

Pollen viability of Polygala paniculata L.(Polygalaceae)using different staining methods

Polygala paniculata L.is a medicinal plant that grows in the Brazilian Atlantic coast,known as‘barba-de-São-João’,‘barba-de-bode’,‘vassourinha branca’,and‘mimosa’.In this study,pollen viability was estimated by three different staining methods:2%acetic orcein,2%acetic carmine,and Alexander’s stain.The young inflorescences of twenty accessions were collected and fixed in a solution of ethanol:acetic acid(3:1)for 24 hours,then stored in ethanol 70%under refrigeration.Six slides per plant,two for each stain,were prepared by squashing,and 300 pollen grains per slide were analyzed.Pollen viability was high(>70%)for most accessions of P.paniculata using the Alexander’s stain,which proved the most adequate method to estimate pollen viability.

The Effect of Air Pollution on Chenopodium album L. Pollen Structure

Air pollution is harm and discomfort to human or other living organisms, it also causes damage to the environment. The aim of this project was to study the effect of air pollutions on structure and pollen grains development in Chenopodium album. Anthers of Chenopodium album L. were collected at different stages of development from control （less polluted） and polluted areas （mainly SO2, NO2, CO and APM）. Structure and development of pollen grains were studied and compared. The effects of pollution on pollen structure was investigated under Light and Scanning electron microscopy and the results showed that when pollen grains were exposed to polluted air they became abnormality in form and covered with large amounts of pollutants compared to control ones. Pollen abnormalities were seen as irregularity, shrinkage, thinning and breakage of the exine. Cellular material release was induced also. The data presented suggest that prolonged exposures of plants to air pollution may cause different biological effects at the cellular tissue and organ levels.

Magnesium transporter AtMGT9 is essential for pollen development in Arabidopsis

Magnesium （Mg^2＋） is abundant in plant cells and plays a critical role in many physiological processes. A 10-member gene family AtMGT （also known as AtMRS2） was identified in Arabidopsis, which belongs to a eukaryote subset of the CorA superfamily, functioning as Mg^2＋ transporters. Some family members （AtMGT1 and AtMGT10） function as high-affinity Mg^2＋ transporter and could complement bacterial mutant or yeast mutant lacking Mg^2＋ transport capability. Here we report an AtMGT family member, AtMGT9, that functions as a low-affinity Mg^2＋ transporter, and is essential for pollen development. The functional complementation assay in Salmonella mutant strain MM281 showed that AtMGT9 is capable of mediating Mg^2＋ uptake in the sub-millimolar range of Mg^2＋. The AtMGT9 gene was expressed most strongly in mature anthers and was also detectable in vascular tissues of the leaves, and in young roots. Disruption of AtMGT9 gene expression resulted in abortion of half of the mature pollen grains in heterozygous mutant ＋/mgt9, and no homozygous mutant plant was obtained in the progeny of selfed ＋/mgt9 plants. Transgenic plants expressing AtMGT9 in these heterozygous plants can recover the pollen phenotype to the wild type. In addition, At- MGT9 RNAi transgenic plants also showed similar abortive pollen phenotype to mutant ＋/mgt9. Together, our results demonstrate that AtMGT9 functions as a low-affinity Mg^2＋ transporter that plays a crucial role in male gametophyte development and male fertility.

Pollen Grain Germination and Pollen Tube Growth in Pistil of Rice

The germination of pollen grain in vitro and the growth of pollen tube in the pistil of rice were observed with a microscope. The stigma was removed at different time points after pollination to study its effect on seed setting rate. The rice pollen grain started to germinate at 2 min after pollination and the pollen tube penetrated stigma into style in 5-10 min, 30 min later the end of pollen tube reached the bottom of ovary, and only some pollen tubes arrived at embryo sac at 40 min after pollination. Meanwhile, a small amount of callose began to deposit in the pollen tubes, a great deal of callose was observed at 50 min after pollination, whereas the pollen grain began to shrink. The growing rates of pollen tube in the rice stigma, style and ovary were 1500, 5000, and 5400 μm/h, respectively. The seed setting rate was quite low when the stigma was removed at about 10-15 min after pollination, gradually increased when it removed at 20 min to 50 min after pollination, and over 60% when it removed at 50 min after pollination and finally tended to be stable.

Effect of the Expression of HSP 70 Gene on the Fertility of Sorghum 1

It was found that the Cytoplasmic Male Sterility (CMS) line of sorghum 3197A (3A) can be induced to become fertile by heat shock treatment, whereas the maintainer line 3197B (3B) is fertile, whether it is heat shocked or not. During the pollen mother cell (PMC) stage, with heat shock treatment, the 3A line changed into fertile from sterile, and five protein bands: 70kD (HSP 70 ), 31kD, 24kD, 18kD and 16kD were found. And identical bands were also appeared in 3B line with similar treatment. By comparing the amount of protein in mitochondria during ear stage of 3A sorghum, the amount of protein increased by 2.7 times, and was almost as much as that in 3B. A comparison of the heat shock proteins (HSPs) of mitochondria in 3A and 3B lines revealed that HSPs were encoded by the nuclear DNA and transported to the mitochondria. Moreover, HSPs were more heat stable in 3B than in 3A line, and this may be related to the stability of fertility in 3B line. To demonstrate the correlation between fertility and HSPs, DNA complementary to HSP 70 was injected into ears of 3A and 3B line. It is found that under normal conditions, there was no HSP 70 mRNA in 3A line, whereas after heat shock this mRNA appeared, and the antisense cDNA could combine with the target RNA of 3B either dealt with normal temperature or heat shocked. These results are discussed within the frame of fertility versus sterility in sorghum.

An Ethylene Over-Producing Mutant of Tomato (<i>Solanum lycopersicum</i>), Epinastic, Exhibits Tolerance to High Temperature Conditions

Above-optimal temperatures reduce yield in many crops, including tomato, largely because of the heat-sensitivity of their reproduction process. A full understanding of heat-stress (HS) response and thermotolerance of tomato reproduction is still lacking. Recently, using external application of the plant hormone ethylene, it was demonstrated that ethylene plays a role in heat-tolerance of tomato pollen (the male reproductive cells). In order to expand our understanding on involvement of ethylene in tomato pollen thermotolerance, we analyzed the response of wild type and ethylene-related tomato mutant plants to HS, at physiological and molecular levels. We report that mild chronic HS conditions highly reduce the number of viable and germinating pollen grains as well as the production of seeded fruits in wild type tomato plants, while no significant reduction was detected/observed in pollen quality, number of seeded fruits and seeds per fruit in plants of the ethylene over-producer mutant epinastic. Our findings suggest that ethylene is involved in thermotolerance of tomato reproduction, pointing to an effect on pollen viability and germination potential, highlighting candidate genes involved in pollen response to HS (like SlHSP17, SlHSP101, SlMBF1) and suggesting directions for further studies.

In vitro anther culture and Agrobacterium-mediated transformation of the AP1 gene from Salix integra Linn. in haploid poplar(Populus simonii × P. nigra)

A reliable,efficient anther culture system,the dominant technique for generating haploid plants in breeding programs,that can be used for generating transgenic poplar plants has been needed.In the present study,therefore,an anther culture system was developed using isolated mid-and late-uninucleate anthers of poplar(Populus simonii x P.nigra).From a combination of SSR and ploidy analyses,six double haploid and two haploid lines were characterized from 86 plants grown from 16 regenerated anther cultured lines.After 48 months of development,two plant lines from the regenerated plants maintained their haploid level in vitro for over 2 years.A number of haploid plants from the different lines weretransferred to soil.The leaves of these transplants were then used as explants for transformation with the APETALA1(AP1) gene using Agrobacterium tumefaciens.Overexpression of AP1 in haploid poplar induced early flowering with obvious petals when ectopically expressed.To our knowledge,this is the first report on changes in flowering time in AP1-trangenic poplar,which is important for elucidating the regulatory mechanism of tree flower development.

Cell Biological Characterization of Male Meiosis and Pollen Development in Rice

Abstract: Little systematic analysis has been undertaken in rice (Oryza sativa L.) on the stages of male meiosis from leptotene to telophase II or of pollen development from microspores to mature pollen grains. The present study describes multiple stages in detail from analysis of rice chromosome spreading with staining of 4′,6-diamidino-2-phenylindole. The description of normal wild-type male meiosis provides an important morphological reference for analyses of meiotic mutants. Meiosis in rice is largely similar to those of the well characterizing model plants Arabidopsis thaliana L. and Zea mays L. However, rice meiosis differs from that in Arabidopsis in that rice meiosis I is followed by the formation of a cell plate, instead of an organelle band that forms between the two nuclei and persist through meiosis II. This suggests a difference in the control of organelle biogenesis and distribution and cytokinesis. Our results should facilitate studies of rice meiosis and pollen development using molecular genetic and cell biological approaches.

Pollen size strongly correlates with stigma depth among Pedicularis species

Summary Darwin proposed that pollen size should be positively correlated with stigma depth rather than style length among species given that pollen tubes first enter the stigma autotrophically, then grow through the style heterotrophically. However, studies often show a posi-tive relationship between pollen size and style length. Five floral traits were observed to be correlated among 42 bumblebee-pollinated Pedicularis species （Orobancha- ceae） in which stigmas are distinct from styles. The phylogenetic independent contrast analysis revealed that pollen grain volume was more strongly correlated with stigma depth than with style length, consistent with Darwin＇s functional hypothesis between pollen size and stigma depth.

High-throughput Procedure for Single Pollen Grain Collection and Polymerase Chain Reaction in Plants

Single pollen grain polymerase chain reaction （PCR） has succeeded in several species, however only limited numbers of pollen grains were involved due to difficulties in pollen isolation and lysis. This has limited its application in genetic analysis and mapping studies in plants. A high-throughput （HT） procedure for collecting and detecting genetic variation in a large number of individual pollen grains by PCR is reported. The HT procedure involved the collection of individual pollen grains by a pair of special forceps and the lysis of pollen grains in a heated alkali/detergent solution followed by neutralization with a tris-ethylenediamine tetraacetic acid （TE） buffer. These resulting template solutions yielded PCR reactions involving the 5S ribosomal RNA intergenic spacers, randomly amplified polymorphic DNA, and simple sequence repeats markers. Using this procedure, one person with experience could collect and process up to 288 single pollen grain PCR reactions per day. The method worked well on sugarcane, corn, Miscanthus spp., snap bean, sorghum, and tomato. The ability to collect and conduct PCR on individual pollen grains on a large scale offers a new approach to genetic analyses and mapping studies in an easily controllable environment with a considerable cost reduction. The method will also significantly benefit studies in species that are difficult subjects for classical genetic research.

Palynomorph assemblage biozonation of Paleogene strata in Bende–Umuahia Area,Niger Delta Basin, southeastern Nigeria

Cenozoic sediments form extensive outcrops in the Niger Delta Basin. Detailed palynostratigraphic study was undertaken across Paleogene sequences exposed in Bende–Umuahia Area in up-dip sectors of the Niger Delta Basin, southeastern Nigeria, to establish different palynomorphs assemblage zones, with their corresponding ages.Palynological analysis was carried out on 27 selected outcrop samples, using the conventional maceration technique for recovering acid-insoluble organic-walled microfossils from sediments. Three Cenozoic lithostratigraphic units, including Imo Formation, Ameki Formation, and Ogwashi Formation, are exposed in the study area. Lithologies are sandstone, carbonaceous shale, mudstone, limestone, and the lignite. A total of 65 species of sporomorphs and 51 dinoflagellate cysts were identified. The recovered spores and pollen grains were used to establish six informal palynomorph assemblage zones, labeled as zone A – zone F, based on the first and the last occurrences of two or more species. These palynomorph assemblage zones include:(1) zone A — middle Paleocene Scabratriporites simpliformis–Bombacidites annae zone;(2) zone B — late Paleocene Foveotricolporites crassiexinus–Mauritidiites crassiexinus zone;(3) zone C — early Eocene Striatopollis catatumbus–Momipites africanus zone;(4) zone D — middle Eocene Margocolporites umuahiaensis–Gemmastephanocolporites brevicolpites zone;(5)zone E — late Eocene Cicatricosisporites dorogensis–Perfotricolpites nigerianus zone;and,(6) zone F — Oligocene–early Miocene Verrucatosporites usmensis–Magnastriatites howardii zone. The erected palynozones were correlated and compared with existing biozones in subsurface, down-dip sectors of the Niger Delta Basin, with pantropical palynological zones in tropical areas of Africa, and with palynofloral provinces of northern South America. A comparison of palynozones studied in southeastern Nigeria with other international palynozones, in this study, will assist in establishing the correlation of sediments for these areas.

ABORTED GAMETOPHYTE 1 is required for gametogenesis in Arabidopsis

In flowering plants, the male and female gameto- genesis is a crucial step of sexual reproduction. Although many genes have been identified as being involved in the gametogenesis process, the genetic mechanisms underlying gametogenesis remains poorly understood. We reported here characterization of the gene, ABORTED GAMETOPHYTE 1 （AOGI） that is newly identified as essential for gametogenesis in Arabidopsis thaliana. AOG1 is expressed predominantly in reproductive tissues including the developing pollen grains and ovules. The AOG1 protein shares no significant amino acid sequence similarity with other documented proteins and is located mainly in nuclei of the cells. Mutation in AOG~ caused degeneration of pollen at the uninucleate microspore stage and severe defect in embryo sacs, leading to a significant reduction in male and female fertility.Furthermore, the molecular analyses showed that the aogl mutant significantly affected the expression of several genes, which are required for gametogenesis. Our results suggest that AOG1 plays important roles in gameto- genesis at the stage prior to pollen mitosis 1 （PMI） in Arabidopsis, possibly through collaboration with other genes.