Histological and Morphological Studies of Pollen Grains from Elongata, Reduced Elongata and Staminate Flowers in Carica papaya L.

The quality and quantity of pollen from three types of flowers; elongata, reduced elongata and staminate from the commercialized Thai papaya cultivar ‘Khak Nual’ were determined using pollen morphology, pollen physical characters and pollen development processes. Pollen development progressed at the same pace in the three types of pollen-producing flowers and was consistent with pollen development in many angiosperms. Pollen morphology showed that papaya pollen grains are tricolporate, with three apertures, and there is no significant difference in diameter (25.18–25.72 μm) and weight (11.76–15.45 ng) among pollen sources. The staminate flower shows the lowest amount of pollen, with 12,368 pollen per anther, but higher viability and germination rates of 95.53 % and 53.64 %, respectively. In contrast, the elongata type shows the highest amount of pollen grains with 14,884 pollen per anther and the lowest viability and germination rates, 93.06 % and 46.33 % respectively. The physical characteristics of pollen grains from reduced elongate and elongate flowers are similar. Reduced elongate flower type can donate pollen without self-pollinating.     

Overexpression of a human α3/4-fucosyltransferase alters pollen development in transgenic tobacco plants

. In plants, the function of Ŏ-fucosylation remains largely unknown. To gain insight into the role of Ŏ-fucosylation during plant development, we generated transgenic tobacco plants overexpressing the human ō/4-fucosyltransferase (hFuc-TIII). Overexpressors clearly contained high amounts of hFuc-TIII and revealed a strong increase in !(1,4)fucosyltransferase activity in plant sexual organs. As a consequence, a more significant staining of Lewis^a motifs, the product of !(1,4)fucosyltransferase activity, was observed in transgenic pollen grains compared to those of controls. Here, we show that pollen grain development was altered in transgenic plants. The average size (polar and equatorial diameters) of mature pollen grains overexpressing hFuc-TIII was smaller than control pollen grains. Furthermore, whereas a reticulate cell wall surface was always observed on control pollen grains, a punctate and disorganized cell wall surface was observed on hFuc-TIII overexpressor pollen grains. In addition, transgenic pollen tube elongation was delayed compared to control pollen tube growth. This latter phenotype could at least explain the 35% reduction of seed production determined for the hFuc-TIII-overexpressing plants.     

The Formation of Pollen Dimorphism in Paris axialis in Vivo

It is obsreved that the dimorphic populations of pollen are producedin Paris axialis H. Li In vivo. The normal pollen grains and abnormal pollen grainsare 77.1% and 22.9% respectively; more than 70% of abnormal pollen grains conformto the equal nucleus type. The abnormal pollen grains show no delayed development,and thay are stained as dark as the normal ones. During the first mitotic division of microspore, most of the spindles are anticlinal(perpendicular to the intine), the cytokinesis is generally asymmetric, and a completewall is formed. However, a few mitotic spindles of mitotic microspores are periclinal,and the cytokinesis are symmetric. Sometimes a partial wall is observed between twodaughter nuclei, which are produced by the abnormal pollen grains. We believe thatthese phenomena are related to differentiation of the dimorphic pollen.     

Pollen Dimorphism and Its Relation to the Formation of Pollen Embryos in Anther Culture of Wheat (Triticum aestivum)

The anomalous pollen grains in vivo at the frequencies of 2.61% and 6.81% respectively were found in anthers of two hybrid materials of wheat from which we had obtained the higher frequencies of induction of pollen embryos in anther culture in the past few years. This indicated that the pollen dimorphism also presented itself in the anthers on wheat plants. A comparative cytological study of development of anomalous pollen grains in vivo and of the early stages of the formation of pollen embryos in vitro was carried out and the results suggest that in cytological details there is an obvious similarity between them. This reveals the possibility that the pollen embryos night derive itself from the anomalous pollen grains in wheat as in the other plants. Therefore, it was considered that the appearance and frequency of the anomalous pollen grains could show the senibility of the development of microspores to the changes of various internal and external factors. The significance of the sensibility for the formation of pollen embryos in anther culture of wheat is discussed.     

Anther culture and cold treatment of floral buds increased symmetrical and extra nuclei frequencies in soybean pollen grains

Androgenic response is characterized by a multinucleate or multicellular stage of pollen development. Histological sections stained with toluidine blue and squashes in propionic-carmine and in 4-6-diamidino-2-phenylindole (DAPI) were used for serial observations (0, 14 and 28 days) in soybean pollen grains from cultured anthers and floral buds submitted to cold treatment at 4 °C. In a total of 62,536 pollen grains, it were observed general averages of 2.06% of pollen grains with two symmetrical nuclei and of 1.41% pollen grains with typical extra nuclei (i.e. additional nuclei with typical morphology). Symmetrical and extra nuclei frequencies increased in both treatments but only the number of pollen grains with typical extra nuclei increased significantly with time of exposure to treatments. In addition, 8.59% of multinucleate pollen grains were recorded with atypical nuclei, smaller than vegetative or generative-types and with a fragmented shape. The frequency of these grains increased significantly with time of exposure to treatments. Thus, soybean multinucleate grains occurrence was not an exclusive response to culture. These preliminary results point to the need of further studies to clarify the relationship between typical and fragmented extra nuclei with both androgenesis and programmed cell death.     

Pollen Dimorphism and Androgenesis of Paeonia in Vivo

It was observed that anthers of Paeonia lactiflora cultivar “Da-Fu-Gui” produced dimorphic pollen grains, i.e. the normal pollen garins and anomalous pollen grains, frequencies of which were 75.8% and 24.2% respectively. Some of the anomalous pollen grains carried out extra divisions (in vivo) and so the multinueleat or multicellular pollen grains were formed. It seem to indicate that there are several different pathways including asymmetric and symmetric divisions and fusion of the nuclei in the androgenesis.     

Sub-haploid pollen inPaphiopedilum insigne (Orchidaceae)

Sub-haploid pollen grains with chromosome numbers ranging from n = 5-12 were seen in the cultivar ‘Maulei’ ofPaphiopedilum insigne Pfitz. Many grains showed n = 5 and 6 (38%) while 3% showed a hyperploid number (n = 18, 20). It was also observed that pollen grains with the same chromosome number differed in karyotype. The high percentage (81 %) of sub-haploid pollen grains in the present case may be due to the high degree of segregational irregularities during meiosis or to split spindle or failure of wall formation. It may also be due to changes in the environment of the species which may influence the metabolic activity responsible for the initiation and subsequent development of the cell wall and the process of chromosome duplication.     

The effect of heat stress on tomato pollen characteristics is associated with changes in carbohydrate concentration in the developing anthers

Continuous exposure of tomato 'Trust' to high temperatures (day/night temperatures of 32/26 degrees C) markedly reduced the number of pollen grains per flower and decreased viability. The effect of heat stress on pollen viability was associated with alterations in carbohydrate metabolism in various parts of the anther during its development. Under control, favourable temperature conditions (28/22 degrees C), starch accumulated in the pollen grains, where it reached a maximum value 3 d before anthesis; it then diminished towards anthesis. During anther development, the concentration of total soluble sugars gradually increased in the anther walls and in the pollen grains (but not in the locular fluid), reaching a maximum at anthesis. Continuous exposure of the plants to high temperatures (32/26 degrees C) prevented the transient increase in starch concentration and led to decreases in the concentrations of soluble sugars in the anther walls and the pollen grains. In the locular fluid, however, a higher soluble sugar concentration was detected under the high-temperature regime throughout anther development. These results suggest that a major effect of heat stress on pollen development is a decrease in starch concentration 3 d before anthesis, which results in a decreased sugar concentration in the mature pollen grains. These events possibly contribute to the decreased pollen viability in tomato.     

Airborne Pollen Grains of Bozuyuk （Bilecik, Turkey）

Airborne pollen grains in the atmosphere of Bozuyuk were investigated over a 2 yr period from 2000 to 2001 using a Durham sampler. A total number of pollen grains of 5 170 pollen grains belonging to 32 taxa were identified and recorded along with some unidentified pollen grains. Of all the pollen grains, 78.66% were arboreal, 19.20% were non-arboreal, and 2.12% were unidentified. The majority of pollen grains investigated were Pinus, Platanus, Quercus, Cupressaceae, Poaceae, Fagus, Salix, Rosaceae, Urticaceae, Asteraceae, and Chenopodiaceae. The maximum number of pollen grains was recorded in May.     

Characterization of pollen tube development in Pinus strobus (Eastern white pine) through proteomic analysis of differentially expressed proteins

The differentially expressed proteins in pollen tubes indicate their specific roles in this stage of male gametophyte development. To isolate these proteins, 2-DE was done using ungerminated pollen and 2-day-old pollen tubes of Pinus strobus. Results show that 645 and 647 protein spots were clearly resolved from pollen grains and pollen tubes, respectively. Thirty-eight protein spots were expressed only in pollen tubes, while 19 increased in intensity. MALDI-TOF MS was used to generate tryptic peptide masses that were submitted to Mascot for identification. Of the differentially expressed proteins, 12% matched with hypothetical proteins, 33% did not hit any protein, and for the 55%, a putative function was assigned based on similarity of sequences with previously characterized proteins. Therefore, pollen tube development can be characterized by the cellular activities that involve metabolism, stress/defense response, gene regulation, signal transduction, and cell wall formation. This study expands our understanding of the changes in protein expression associated with pollen tube development and provides insights into the molecular programs that separate the development of the pollen tubes from pollen grains. This is the first report that describes a global analysis of differentially expressed proteins from the pollen tube of any seed plant.     

雄性不育相关基因msLTP的反义RNA验证

根据普通白菜雄性不育相关的脂质转移蛋白基因(msLTP)的cDNA序列设计引物,从普通白菜花蕾的cDNA中扩增出312bp的片段,然后将该片段连接至双元载体pBI12l中,得到反义RNA植物表达载体并导入农杆菌LBA4404菌株中,通过农杆菌介导法转化菜心;利用PCR和Southern blot分析检测得到了25株转基因植株,转基因植株的花粉部分畸形或空瘪,花粉离体萌发率为38.56%,较未转化植株的萌发率(76.32%)降低了37.76个百分点.研究表明,反义RNA技术使msLTP基因沉默而导致了菜心转基因植株的部分花粉发育不良,说明msLTP基因在普通白菜和菜心等花粉发育中具有重要作用.     

濒危植物红花木莲小孢子发生及雄配子体发育的研究

首次报道了木莲属胚胎学特性,研究了红花木莲Manglietia insignis(Wall.)Bl.的小孢子发生、雄配子体的发育以及花粉萌发情况,红花木莲花药具有４个小孢子囊。花药壁５－６层,腺质绒毡层具有２－层细胞,小孢减数分裂后胞质分裂为修性同时型;四个分体排列方式为交叉型或左右对称型,偶为直线型;成熟花粉为二细胞型花粉粒,同时报道了化粉木莲在小孢子发生过程中的特有的现象,花粉萌发率为１４．７％－２５．３％。联系红花木莲花粉粒数目和胚珠数目进行探讨,认为雄配子体发育不是影响红花木莲结籽率低的主要因素。     

长花柱型滇丁香小孢子发生及雄配子体发育

利用常规石蜡切片法和细胞学压片法,对异型花柱植物滇丁香的长花柱型植株的小孢子发生、雄配子体发育及花粉萌发进行观察。结果表明:(1)长花柱型滇丁香具5枚花药,花药4室。(2)花药壁由1层表皮、1层花药内壁、2层中层和1~3层绒毡层组成;花药壁发育方式为基本型,绒毡层类型为腺质绒毡层。(3)小孢子母细胞减数分裂的胞质分裂为同时型,四分体排列方式为四面体型,偶有左右对称型;不同药室间小孢子母细胞减数分裂不同步。(4)成熟花粉粒为二细胞型。(5)小孢子发生和雄配子体发育过程正常,表明长花柱型滇丁香属于发育正常的两性花。(6)授粉4h后,长花柱型滇丁香的花粉在长、短两种花柱柱头上的萌发率分别达(91.8±1.6)%和(93.2±1.1)%,且两者间无显著性差异(t=1.585,df=8,p=0.152),表明长花柱型滇丁香的成熟花粉粒在长、短两种花柱柱头上的萌发均正常。     

An efficient and rapid transgenic pollen screening and detection method using flow cytometry

Assaying for transgenic pollen, a major vector of transgene flow, provides valuable information and essential data for the study of gene flow and assessing the effectiveness of transgene containment. Most studies have employed microscopic screening methods or progeny analyses to estimate the frequency of transgenic pollen. However, these methods are time-consuming and laborious when large numbers of pollen grains must be analyzed to look for rare transgenic pollen grains. Thus, there is an urgent need for the development of a simple, rapid, and high throughput analysis method for transgenic pollen analysis. In this study, our objective was to determine the accuracy of using flow cytometry technology for transgenic pollen quantification in practical application where transgenic pollen is not frequent. A suspension of non-transgenic tobacco pollen was spiked with a known amount of verified transgenic tobacco pollen synthesizing low or high amounts of green fluorescent protein (GFP). The flow cytometric method detected approximately 75% and 100% of pollen grains synthesizing low and high amounts of GFP, respectively. The method is rapid, as it is able to count 5000 pollen grains per minute-long run. Our data indicate that this flow cytometric method is useful to study gene flow and assessment of transgene containment.     

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 14367 pollen grains belonging to 40 taxa have been identified and recorded with some unidentified ones.Of them,6732 were identified in 1999 and 7635 in 2000.Of the total pollen grains,69.67% were arboreal,26.64% on-arboreal and 3.68% unidentified.The majority of the investigated pollen grains were from Pinus,Granineae,Cupressaceae,Platamus,Chenopodiaceae/Amaranthaceae,Quercus,Ailanthus,Moraceae,Juglans,Salix,Cedrus and Rosaceae.The highest level of pollen grains was in May.     

Pollen diversity in the atmosphere of Havana,Cuba

With a view to obtaining fuller information on airborne pollen content in the city of Havana, pollen sampling was carried out using a volumetric capture method, for the first time in Cuba. The study was conducted during 2 years (2011 and 2015). An annual pollen integral of 3414 grains was registered during the first year of study, whereas 5120 grains were observed along the 2015. Monthly maximum concentrations were recorded during April, June and July with total values close to 800 pollen grains. Of the 45 pollen types identified, Cecropia (38% of the total pollen identified in both years), Poaceae (18%), Urera type (9%) and Casuarina (6%) were particularly abundant. Although the main pollen types differed in terms of intradiurnal distribution, the highest concentrations were in all cases recorded between 0900 and 1300 hours. Maximum temperature was the variable most influencing airborne pollen counts in the air, with the exception of Casuarina. This paper sought to establish a methodological basis for the further development of aerobiological research in Cuba, thus helping to enhance the prevention and diagnosis of pollen allergies in the affected island population.     

Pollen dynamics of bumble-bee visitation on Echium vulgare

1. We quantified pollen deposition on the stigma, pollen removal from the anthers and pollen losses in Echium vulgare , visited by workers of Bombus terrestris under controlled conditions. We used dye as a pollen analogue. Bumble-bees were trained to visit a sequence of non-emasculated flowers to estimate pollen carryover and to visit individual flowers to estimate pollen loss.
2. Carryover of pollen grains and dye particles between flowers was similar, which justifies using dye as a pollen analogue. On average 93·8% of the dye particles on the bee were carried over to the next flower. Only a small fraction of the pollen grains was deposited on the stigma (0·15%). A much larger fraction (6·1%) was lost in another way: passively during flight, through grooming or on floral parts other than the stigma. The bees removed 44% of the pollen grains from a fresh flower and 50·3% of this removed pollen adhered to the bee.
3. We predict that, using the parameters mentioned above, during a single visit to a newly opened flower, a bee collects an amount of pollen grains which will bring about 60% geitonogamous self-pollination in the next flower visited. The expected percentage of self-pollination is considerably less if bees visit flowers that have been visited before.     

Digestibility of columnar cacti pollen grains in the glosophagine bats Glossophaga longirostris and Leptonycteris curasoae (Chiroptera: Phyllostomidae)

We examined the protoplasmic assimilation of columnar cacti pollen grains in two species of Venezuelan desert glosophagine bats, Glossophaga longirostris and Leptonycteris curasoae, by determining the amount of empty (digested) pollen grains found in their fecal samples. To determine the amount of empty pollen grains, the fecal samples were stained to differ between empty and full (non-digested) pollen grains. The number of empty and full pollen grains observed in the fecal samples were corrected using the amount of aborted pollens present (before anthesis) in flowers of the columnar cacti species (Subpilocereus repandus, Stenocereus griseus and Pilosocereus tillianus) used by bats as food in the study site; G. longirostris and L. curasoae digested 64.2% and 71.3% of all the pollens fed, respectively. These high values confirm the importance of pollen in the diet of these bats, given its high nitrogen level.     

Development and cytochemistry of pollen and tapetum in Mitriostigma axillare (Rubiaceae)

The development of pollen grains and tapetum in Mitriostigma axillare (Rubiaceae) was studied from anther primordium to dehiscence. Anthers were freeze-cracked and studied with SEM. Embedded anthers were sectioned and studied with LM and TEM. Cytochemistry was performed in order to distinguish the different layers of the sporoderm and to determine its chemical nature at different development stages. The pollen grains remained as tetrads by partial fusion of the exine, probably because of reduced callose septa during the stage of microspore tetrads within callose envelopes. Characteristic features of the sporoderm were an irregular foot layer, an endexine composed of amalgamated granules, a transient granular-fibrous layer beneath the endexine, and a thin intine. During maturation of the exine, the endexine became chemically different from the ectexine. All layers of the sporoderm were reduced in thickness due to stretching during the engorgement of the pollen grains prior to dehiscence. The pollen grains were colpoidorate with a reticulate to microreticulate tectum covered with a scanty surface coating. The mature pollen grains were binucleate and contained a lot of starch grains. Thick intineous onci protruded through the apertures and formed papillae. About 50% of the microspores were aborted. The tapetum was of secretory type, probably with cycles of hyperactivity and protrusions of the cells into the locular cavity. No syncytium was formed and there were neither orbicules nor tapetal membrane.