Pistil Receptivity and Pollen Tube Growth in Relation to the Breeding System of Eucalyptus woodwardii (Symphyomyrtus: Myrtaceae)

Pistil structure, stigma receptivity and pollen tube growthwere investigated in relation to seed set of Eucalyptus woodwardii.Self-pollination resulted in reduced capsule retention and seeddevelopment as compared with cross-pollination. The pistil consistedof an ovary with five locules, a long style with a canal extendingfor two-thirds of its length, and a papillate stigma. Therewas no change in style length with time after anthesis, butboth stigma secretion and ability to support pollen germinationand tube growth increased to reach a peak at 7 d. Pollen germinatedon the stigma surface and in the stylar canal, but most tubegrowth occurred intercellularly in the transmitting tissue surroundingthe canal. At the base of the style the pollen tubes split intofive groups following the transmitting tissue strands to theovary. Each group grew through a septum dividing two loculesand entered the placenta. The tubes then emerged from the placentato penetrate the ovules at between 10 and 20 d after pollination.Fewer ovules were penetrated following self- than cross-pollination. Eucalyptus woodwardii Maiden, Lemon-flowered gum, Pistil receptivity, Pollen tube growth, Breeding system, Self-incompatibility     

Altitudinal variation in Leptospermum flavescens Sm. (Myrtaceae)

Correlation of altitude with morphological data from herbarium specimens of two taxa within the Leptospermum flavescens group indicates that, in the Sydney region, there is a convergence of leaf and flower size at higher altitudes. There are also altitudinal differences in germination ability, growth rate and leaf chemistry. Experimental evidence suggests that at least some of this altitudinal variation is genetically fixed within the populations.     

Pistil Exudate Production and Pollen Tube Growth in Lilium longiflorum Thunb.

Exudate production in the pistil of Lilium longiflorum was studiedin relation to pollen tube growth, using scanning electron microscopy(SEM), transmission electron microscopy and light microscopy.In contrast with conventional fixation for SEM, during whichthe exudate of L. longiflorum largely washes away, the exudateremains present through freezing in case of cryo-SEM. Usingthe latter method we observed that exudate production on thestigma and in the style started before anthesis. Just underneaththe stigma the exudate was first accumulated at the top of eachsecretory cell, followed by a merging of those accumulationsas exudate production proceeded. Exudate is also produced bythe placenta. It was however not possible to determine whetherany of this fluid originated from the micropyle. Apart fromthe cell shape and the cuticle present in between the secretorycells, the ultrastructure of the secretory cells covering theplacenta was comparable to those of the stylar canal. The transferwall of the secretory cells of the placenta originated fromfusing Golgi vesicles but the endoplasmic reticulum seemed tohave an important role as well. After pollination the pollen tubes grew across the stigma andentered the style through one of the slits in the three stigmalobes. The pollen tubes grew straight downward through the styleand were covered by exudate. As the pollen tubes approachedthe ovary their growth was restricted to the areas with secretorycells. In the cavity the pollen tubes formed a bundle and theybent from this bundle in between the ovules towards the micropylarside. There they bent again to stay close to the secretory cells.After bud pollination the pollen tube growth was retarded. Laterarriving pollen tubes had a tendency to grow close to the secretorycells of the style, which resulted in a growth between thesecells and preceding pollen tubes. If there was still a littleexudate produced, it resulted in a lifting up of the pollentubes, out of the exudate. The relationship between exudateproduction and pollen tube growth is discussed. Both the speedand the guidance of the pollen tube seemed determined by theproperties of the exudate.Copyright 1994, 1999 Academic Press Cryo-scanning electron microscopy, exudate, Lilium longiflorum, lily, ovary, pollination, pollen tube growth, secretory cell, stigma, style     

Pre-dispersal seed losses to insects in species of Leptospermum (Myrtaceae)

Pre-dispersal seed losses to insects in species of Leptospermum at Wilson's Promontory in south-eastern Australia varied markedly between species, seasons, sites and individuals. The proportion of fruits attacked by insects averaged 11% (range 3–37%) in populations of Leptospermum juniperinum, 23% (6–95%) in Leptospermum myrsinoides, 23% (0–47%) in Leptospermum laevigatum, and 28% (8–45%) in Leptospermum lanigerum. The proportion of seeds lost in attacked fruits also varied widely. Differences between species varied markedly from year to year, but differences between sites were relatively constant. Fruit production by L. myrsinoides was unusually low at most sites during 1984; in each case this coincided with unusually high rates of insect attack, suggesting that predator satiation operates during normal seasons.     

The Pollen Tube Pathway in the Pistil of Lycopersicon peruvianum

The pollen tube pathway has been studied in unpollinated andpollinated pistils of Lycopersicon peruvianum using histochemicalstains for detection of proteins, lipids and arabinogalactansby bright-field microscopy, and decolourized aniline blue fordetection of pollen tubes by epifluoresence microscopy. Thepollen tube pathway is a continuous tract of mucilage from thestigma surface to the ovule micropyles, and is associated witha continuous tract of specialized, protein-rich transmittingcells comprising the stigmatic papillae, vertical files of stylartransmitting cells and the placental epithelium within the ovary.The superficial exudate of the stigma is hydrophobic and richin lipids. The mucilage of the style and ovary is hydrophilicand rich in arabinogalactans but low in proteins. Pollen tubesgrow between cells through the mucilage of the stigma and stylartransmitting tract, and across the surface of the placenta inthe ovarian mucilage. The structure of the junction of the stylartransmitting tract with the top of the ovary placenta assistseffective distribution of pollen tubes within the ovary. Lycopersicon, solanaceae, fertilization, pistil, pollen tube, pollination     

雌蕊胞外基质在花粉管生长中的作用

雌蕊胞外基质对雌蕊与花粉的识别以及花粉管的定向生长有着重要的作用,是近年来植物生殖生物学的研究热点之一。与花粉萌发和花粉管生长相关的雌蕊胞外基质种类主要包括阿拉伯半乳糖蛋白、类伸展素糖蛋白、富含脯氨酸糖蛋白、钙调素、S—糖蛋白、果胶以及子房的特异性物质等。本文着重介绍这些雌蕊胞外基质的生理功能及其研究进展。     

雌蕊胞外基质在花粉管生长中的作用

雌蕊胞外基质对雌蕊与花粉的识别以及花粉管的定向生长有着重要的作用,是近年来植物生殖生物学的研究热点之一。与花粉萌发和花粉管生长相关的雌蕊胞外基质种类主要包括阿拉伯半乳糖蛋白、类伸展素糖蛋白、富含脯氨酸糖蛋白、钙调素、S-糖蛋白、果胶以及子房的特异性物质等。本文着重介绍这些雌蕊胞外基质的生理功能及其研究进展。     

Structure and development of the elaiosome in Myrtus communis L. (Myrtaceae) seeds

Myrtus communis L. (Myrtaceae) is a fleshy-fruited shrub occurring in the Mediterranean area, whose seeds are snail shaped, with a very thick coat and a central elaiosome. This structure is a fleshy and edible appendage responsible of seed dispersal by ants, a phenomenon known as myrmecochory. The elaiosome develops very early from the external integument cells near the funicular and micropylar area, through cell enlargement and cell divisions. At the latest stages of development, some internal integument cells participate to its formation so that myrtle elaiosome can be classified among those originating from both epidermal and inner tissues.The low content of lipids, starch and proteins revealed by histochemical and biochemical analyses on M. communis elaiosomes suggests that the myrtle is a plant with a multiple pattern of seed dispersal. Myrmecochory seems to play a secondary role.     

Pollen Tube Distribution in the Kiwifruit (Actinidia deliciosaA. Chev. C. F. Liang) Pistil in Relation to its Reproductive Process

High resolution light and fluorescence microscopy were usedto investigate the structural and cytochemical features of thekiwifruit(Actinidia deliciosa)pistil and to follow the pollentube pathway after pollination. The multicarpellary ovary issyncarpous only at the ovary level thus leaving 30–40free styles on top. The fusion of the longitudinally-foldedcarpels to form the syncarpous ovary forms a central parenchymatousaxis, the columella, from which the ovules radiate outwardsinto the ovary cavity. A prominent cup shaped depression onthe columella at the top end of the ovary, termed the pollentube distributor cup (PTDC) was detected. Pollen tubes fromthe stigma travel through the transmitting tract and enter thePTDC from where they are distributed towards the ovary. Evenwhen pollination is restricted to two stigmas, the PTDC seemsto ensure that the pollen tubes are evenly distributed aroundthe ovary resulting in an even distribution of seeds. This suggestedrole of the PTDC which could compensate for over and under pollinationof individual stigmatic arms is another adaptive feature whichplays a crucial role in the reproductive process of kiwifruit.The significance of this structure for pollination by insectsis discussed.Copyright 1998 Annals of Botany Company Actinidia deliciosa, kiwifruit, pollination, floral anatomy, reproductive success, pollen tube distribution.     

Plant speciation on tropical mountains: Leptospermum (Myrtaceae) on Mount Kinabalu, Borneo

The genus Leptospermum (Mytaceae) is represented on Mount Kinabalu, Borneo, by L.flavescens (widespread on Malesian mountains and uplands) and L.recurvum (endemic to Mount Kinabalu). Analysis of the general morphology, leaf characters, leaf anatomy and flavonoid content of field collection, of both taxa at 1970–4000 m indicated that L.recuruum is a distinct species, most probably derived from L.flavescenS. L.recurvum individuals display a striking variation in leaf pubescence. Seedlings of. These plants grown under uniform conditions were not genetically variable (as seen in the uniformity of peroxidase and acid phosphatase isozymes).Variation that did occur was not correlated with altitude or any other identifiable ecological factors. The sporadic distribution of individuals producing non-viable seeds, probably an expression of genetic load, is another indication of a lack of genetic diversity. L.recurvum may have evolved from a population of L.flaurscens on Mount Kinabalu, most probably during the Pleistocene.     

Floral Viability and Pollen Tube Growth in Vicia faba L.

Durations of stigmatic receptivity, pollen viability and pollen tube growth were investigated in the largely entomophilous faba bean. Stigmas were examined for deposited and germinated pollen, and growth of pollen tubes was investigated using aniline blue-induced fluorescence. Entry of a pollen tube into a micropyle was found to be a reliable indicator of fertilization. After anthesis, stigmas remained receptive to pollination for six days, and pollen viable for five. Pollen tubes took up to three days to reach the ovules furthest from the stigma. Inspection of ovular development within pods showed that the incidence of fertilization had been accurately determined in the flowers.     

Pollen Tube Cytoskeleton: Structure and Function

   apd: 3 July 2001     

Floral Biology, Pollination, Pistil Receptivity, and Pollen Tube Growth of Teak (Tectona grandis Linn f.)

Teak flowers are weakly protandrous and pollen is shed withina few hours of flower opening. Pollen is tricolpate and 29 µmin diameter. The papillate stigma is of the wet type and isreceptive from 1100–1300h. The style is hollow throughoutits length. Nectar and pollen are the major floral rewards forpollinators. The major pollinators areCeratina sp. which carryteak pollen on most parts of their bodies, especially the specializedhair structures (scopal brushes) on the tibia. The most effectivepollination period in terms of flowers pollinated and pollenper flower is between 0900 and 1300h. At 1300h the number ofpollen per flower is the highest, ranging from 1–36 (average7). Pollen tubes grow very fast. Within 2 h after pollination8% of the pollen tubes have reached the micropylar end of theovule and pollen tubes first enter the embryo sac at 8 h. Onlyone to two pollen tubes enter the micropyles of a flower. Although78% of flowers were pollinated in open-pollination, the lowfruit set (3.5%) suggests that there are factors other thanpollination limiting fruit set. The main factor appears to bea high amount of selfing, and self-incompatibility occurs whenpollen tubes are arrested at the lower portion of the ovary. Tectona grandis ; floral biology; pollen tube growth; pollination; receptivity; pollinators     

Pollen Tube Growth: a Delicate Equilibrium Between Secretory and Endocytic Pathways

Although pollen tube growth is a prerequisite for higher plant fertilization and seed production, the processes leading to pollen tube emission and elongation are crucial for understanding the basic mechanisms of tip growth. It was generally accepted that pollen tube elongation occurs by accumulation and fusion of Golgi-derived secretory vesicles (SVs) in the apical region, or clear zone, where they were thought to fuse with a restricted area of the apical plasma membrane (PM), defining the apical growth domain. Fusion of SVs at the tip reverses outside cell wall material and provides new segments of PM. However, electron microscopy studies have clearly shown that the PM incorporated at the tip greatly exceeds elongation and a mechanism of PM retrieval was already postulated in the mid-nineteenth century. Recent studies on endocytosis during pollen tube growth showed that different endocytic pathways occurred in distinct zones of the tube, including the apex, and led to a new hypothesis to explain vesicle accumulation at the tip; namely, that endocytic vesicles contribute substantially to V-shaped vesicle accumulation in addition to SVs and that exocytosis does not involve the entire apical domain. New insights suggested the intriguing hypothesis that modulation between exo- and endocytosis in the apex contributes to maintain PM polarity in terms of lipid/protein composition and showed distinct degradation pathways that could have different functions in the physiology of the cell. Pollen tube growth in vivo is closely regulated by interaction with style molecules. The study of endocytosis and membrane recycling in pollen tubes opens new perspectives to studying pollen tube-style interactions in vivo .     

Foliar anatomy and micromorphology of eleven species of Eugenia L. (Myrtaceae)

The anatomy and micromorphology of eleven species of Eugenia found in the 'restinga' of Marica, Rio de Janeiro, Brazil, were studied and compared. The characteristics found to be of most use in distinguishing the species are: presence and types of trichomes persistent in the adult material, form and arrangement of overlying cells (epidermal cells over secretory cavities), pattern of anticlinal walls of epidermal cells (primary sculpturing), occurrence of epicuticular striae and folds (secondary sculpturing) and presence of peristomatal folds. An analytical key based on these characteristics is presented for the Eugenia species studied.     

Identical genotypes of an ericoid mycorrhiza-forming fungus occur in roots of Epacris pulchella (Ericaceae) and Leptospermum polygalifolium (Myrtaceae) in an Australian sclerophyll forest

Assemblages of fungi associated with roots of cooccurring Epacris pulchella ( Ericaceae ) and Leptospermum polygalifolium ( Myrtaceae ) seedlings at a sclerophyll forest site in New South Wales, Australia, were investigated by direct DNA extraction and analysis of rRNA gene internal transcribed spacer (ITS) products by denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) analyses. While ordination of the DGGE data suggested that the assemblages did not differ significantly between the two plant taxa, T-RFLP data provided marginal statistical support for the presence of different assemblages. Fungi isolated from roots of both plants were identified by ITS sequence comparisons largely as ascomycetes, several of which had close sequence identity to Helotiales ericoid mycorrhizal (ERM) fungi. One isolate morphotype from E. pulchella had close sequence similarity to ectomycorrhizal fungi in the Cenococcum geophilum complex, and neighbour-joining analysis grouped this strongly with other Australian C. geophilum- like sequences. Distribution of genotypes of an ERM Helotiales ascomycete in root systems of the two plant taxa was also investigated using inter-simple sequence repeat (ISSR)-PCR. Nineteen ISSR genotypes were identified, two of which were present in roots of both plant taxa. The results are discussed in the context of potential mycelial connections between Ericaceae and non- Ericaceae plants.     

The Nutritional Role of Pistil Exudate in Pollen Tube Wall Formation in Lilium longiflorum: I. Utilization of Injected Stigmatic Exudate

A quantity of labeled stigmatic exudate, collected from detached Lilium longiflorum (cv. Ace) pistils labeled with d-glucose-1-¹⁴C, was fractionated on Sephadex G-100 and the polysaccharide component, G-100-I, was injected into the hollow styles of unlabeled detached pistils (cv. Ace) which had been removed on the day after anthesis from the plant. Injected pistils were immediately cross-pollinated with L. longiflorum (cv. No. 44) pollen. Eighty-four hours later, pistils were dissected to recover the pollen tubes, expended exudate, and labeled tissues of the stigma and style. Distribution of label revealed that at least 25% of the carbohydrate substance in excised pollen tubes was derived from G-100-I. The composition of expended exudate adhering to pollen tubes, of pollen tube cytoplasm, and of pollen tube walls suggests that utilization of exudate by growing pollen tubes involves uptake and incorporation into pollen tube cytoplasm of exudate polysaccharide fragments followed by extensive metabolism of at least a portion of the incorporated carbohydrate prior to its utilization for pollen tube wall biosynthesis. Results suggest the presence of at least two polysaccharide components in G-100-I, one which resists major degradation following injection into the style and another which undergoes measurable degradation both before and after entry into the pollen tube.