Abstract: I measured phenotypic selection of floral traits through both male and female functions of the hermaphroditic flowers of Ipomopsis aggregata (Pursh) V. Grant subsp. aggregata (Polemoniaceae). Fluorescent powdered dyes were used to track movement of pollen by hummingbirds and to measure pollen delivery to individual plants as well as pollen receipt. A phenotypic selection analysis revealed that selection due to male-male competition during pollination was capable of delaying flowering date and widening corolla tubes by 0.22 and 0.24 standard-deviation units, respectively, in a single generation. Several floral traits were highly correlated with each other. Multivariate selection analysis suggested that selection through male function directly favored late flowering as well as a sexual expression characterized by a short pistillate phase and long corollas. Selection intensities through male and female functions were of similar overall magnitude during the pollination stage of the life cycle, but different traits were favored, and selection sometimes acted in opposing directions. In 1985, selection through female function favored increased time spent in the pistillate phase and exserted stigmas (unlike selection through male function). As a result, individual plants varied greatly in functional gender. Plants that had exserted stigmas and narrow corollas and that spent a disproportionately long time in the pistillate phase achieved greater pollination success as females, while plants with the opposite traits achieved greater success as males. Moreover, female pollination success tended to increase, and male pollination success to decrease, with time spent in the pistillate phase, supporting a critical assumption of sex-allocation theory. Selection in the populations studied fluctuated from year to year and was highly sex-specific.

Abstract: In the Mediterranean area there are characteristic climatic conditions (mildness of winter, summer dryness, etc.) that facilitate the growing of a typical vegetation with production of allergenic pollen, such as those from Parietaria and Olea europaea, very different from that of central and northern Europe. We present in this article the results of an 8-year pollen count in the atmosphere of Naples, Italy. The pollen content was examined with a volumetric spore trap (Lanzoni VPPS-2000) like that of Hirst. The results of the pollen counts were subsequently compared with results of skin tests of patients born and still living in and around Naples to determine the pollinosis of that area. We found that the most important allergenic pollen in the Naples area is Parietaria, with very long-lasting periods of pollination. The first period, more important, occurring from March to July, and the second period of much lower intensity, occurring from the end of August to the end of October. Pollen allergy to Parietaria was found to be present in 82.02% of pollen-allergic patients. It was followed by Gramineae (32.12%), Olea (23.11%), and Artemisia vulgaris (17.08%). These data are quite different from data of the pollinosis in northern Italy and in the northern Mediterranean area, as well as the southern coast of France, where allergic sensitization to Poaceae is the most important.

Abstract: Pollen dispersal success in entomophilous plants is influenced by the amount of pollen produced per flower, the fraction of pollen that is exported to other flowers during a pollinator visit, visitation frequency, and the complementarity between pollen donor and recipients. For bumble bee-pollinated Polemonium viscosum the first three determinants of male function are correlated with morphometric floral traits. Pollen production is positively related to corolla and style length, whereas pollen removal per visit by bumble bee pollinators is a positive function of corolla flare. Larger-flowered plants receive more bumble bee visits than small-flowered individuals. We found no evidence of tradeoffs between pollen export efficiency and per visit accumulation of outcross pollen; each was influenced by unique aspects of flower morphology. Individual queen bumble bees ofthe principal pollinator species, Bombus kirbyellus, were similar in male, female, and absolute measures of pollination effectiveness. An estimated 2.9% of the pollen that bumble bees removed from flowers during a foraging bout was, on average, deposited on stigmas of compatible recipients. Significant plant-to-plant differences in pollen production, pollen export per visit, and outcross pollen receipt were found for co-occurring individuals of P. viscosum indicating that variation in these fitness related traits can be seen by pollinator-

Abstract: We have found that the most probable cause of the leakage seen when dry cells or organisms such as seeds, pollen, or yeast cells are plunged into water is a gel to liquid crystalline phase transition in membrane phospholipids accompanying rehydration. By using Fourier transform infrared spectroscopy we have recorded infrared spectra of CH2 stretching vibrations in dry and partially hydrated intact pollen grains of Typha latifolia. The vibrational frequency changes abruptly as phospholipids pass through the gel to liquid crystalline phase transition. Below the apparent transition, viable pollen shows low germination and high leakage when placed in water, but above the transition germination increases and leakage decreases. The apparent transition temperature falls with increasing water content, much as in pure phospholipids. By using this phenomenon, it was possible to construct a hydration-dependent phase diagram for the intact pollen. This phase diagram has immediate applications since it has high predictive value for the viability of the pollen when it is placed in water.

Abstract: Publisher Summary The angiosperm life cycle consists of two alternating phases—a diploid, morphologically elaborate and conspicuous sporophyte, and a much reduced, haploid gametophyte. At least four phenomena in the ontogeny of pollen impinge on the genetic determination of pollen quality: Cytoplasmic interconnections, which establish developmental synchrony among meiocytes, callose envelopes, which isolate microspores from each other, tapetal deposits, which coat the pollen exine, and sporophytic inputs, which remain in the meiocyte cytoplasm. Some pollen characteristics are determined exclusively by the sporophyte, as is the case with the exine. Others, such as Ga factors, gametophytic self-incompatibility, and the presence of specific enzymes (alcohol dehydrogenase, P-galactosidase, are under gametophytic control. Pollen competition may be significant phenomenon in the evolution of crop species and also in the reduction of genetic load. Pollen competition may play a significant role in the adaptive capacities of the angiosperms, as this group possesses three characteristics, which enhance pollen tube competition. These are: Heavy stigmatic loads of pollen, the simultaneous arrival of many pollen grains on the stigma, and the requirement for extensive pollen tube growth. Finally, direct and indirect in vivo interactions between pollen grains and particularly pollen-pistil interactions need evaluation.

Abstract: Myosin, detected by immunofluorescence using an antibody to bovine skeletal and smooth muscle myosin, has been localised on individual identifiable organelles from the grasses Alopecurus pratensis and Secale cereale, and on the surfaces of vegetative nuclei and generative cells from pollen and pollen tubes of Hyacinthus orientalis and Helleborus foetidus. Taken in conjunction with recent evidence showing that the growing pollen tube contains an actin cytoskeleton consisting of numerous mainly longitudinally oriented microfilament bundles, and that isolated pollen-tube organelles show ATP-dependent movement along the actin bundles of the giant cells of the characeous algae, this finding suggests that an actomyosin motility system is present in pollen tubes, and indicates that the movements of the different classes of inclusions are driven by interaction of the surface myosin with the actin fibrils at the zones of contact.

Abstract: Beta-glucuronidase (GUS) was histochemically analyzed in anthers and pollen of potato, tobacco and tomato. GUS activity was determined in transgenic plants containing a chimaeric GUS gene and in untransformed plants. In anthers of transgenic plants at premeiotic and meiotic stages of sporogenous development, indigogenic precipitation indicative of GUS activity was consistently manifest in cells of the vascular cylinder, the connectivum and the stomium while no activity was found in the tapetal and sporogenous tissues. At similar stages, anther sections of untransformed plants did not show any indigo blue staining. At later stages of microspore and pollen development, anthers of both transgenic and untransformed plants demonstrated consistently high levels of GUS activity in tapetal and sporogenic cells. In anthers of transgenic plants, GUS was also present in the vascular cylinder, the connectivum and the stomium. These results indicate that in anthers of transgenic potato, tobacco and tomato the chimaeric GUS gene product was localized tissue specifically. They also show that an endogenous GUS gene was expressed in a temporal- and spatial-specific manner in the tapetum and pollen of both transformed and untransformed plants.

Abstract: Pollen from three S-genotypes of Nicotiana alata was grown in vitro in the presence of S-glycoproteins isolated from styles of the same three genotypes. Pollen germination was not affected by the presence of the S-glycoproteins, but pollen tube growth of all genotypes was inhibited. S2 pollen was preferentially inhibited by the S2-glycoprotein and S3 pollen by the S3-glycoprotein. The S6-glycoprotein preferentially inhibited growth of both S2 and S6 pollen over S3 pollen. Heat treatment dramatically increased the inhibitory activity of the S-glycoproteins as inhibitors both of pollen germination and tube growth; after heat treatment, S-allele specificity of pollen tube inhibition was not detected.

Abstract: One explanation for low fruit sets in plants with hermaphroditic flowers is that total flower production by a plant is controlled primarily by selection through male function. This male function hypothesis presupposes that success in pollen donation increases more strongly with flower number than does seed set. I tested this prediction by measuring male and female components of reproductive success as functions of flower number in natural populations of the self-incompatible, perfect flowered plant, Ipomopsis aggregata. Fruit set in this hummingbird-pollinated plant averaged 4.9 to 40.3% across the 4 years of study. Both the total amount of pollen donated and the total amount received, as estimated by movement of fluorescent powdered dyes, increased linearly with number of flowers on a plant. Total seed production, however, increased disproportionately quickly because plants with larger floral displays were more likely to set at least one fruit. An estimate of the functional femaleness of a plant, based on pollen donation and seed production, increased with flower number. These results do not support the male function hypothesis.

Abstract: Estuarine sedimentation rates are estimated for vertical increments of sediment cores by adjusting average rates between dated horizons with the ratio of pollen concentration to concentration of sediment. The method assumes independent influxes of pollen and sediment into the estuary, similar patterns of transport and deposition for both pollen and fine sediment, a uniform influx of pollen over the time interval between dated horizons, and preservation of the majority of pollen entering the estuary. Comparisons of detailed, pollen-derived sedimentation rates with historical records of climatic and anthropogenic events in upper Chesapeake Bay show that highest rates of sediment accumulation occur in upper and middle stretches of tidal tributaries and coincide with major storms and periods of intensive land clearance when >20% of total land area in a given watershed is deforested and under cultivation.

Abstract: We examined factors affecting the duration of the staminate and pistillate phases in the protandrous flowers of Campanula rapunculoides L. (Campanulaceae). Under conditions of natural pollinator visitation, flowers experiencing low rates of pollen removal lasted significantly longer than flowers that had faster rates of pollen removal. Experimental manipulations showed that low levels of pollen removal resulted in extension of the staminate phase. Hand-pollinations in which we varied the amount and source of pollen showed that when the number of fertilized ovules within an ovary is low, senescence of the flower is delayed, resulting in extension of the pistillate phase. We also report on pollinator foraging patterns within the vertical inflorescences of C. rapunculoides and the limiting factor for seed set in this population. The results are relevent to recent suggestions that floral characters often serve to reduce interference between the sexual functions in cosexual plants.

Abstract: In the past, in vitro cultures of excised anthers and isolated pollen have been used to study normal male sexual development (gametophytic development) and, conversely, to produce and study haploid plant formation (sporophytic development). For years both branches have existed side by side, without much interaction. Today, a synthesis of the two branches is possible as well as necessary. Recent advances in the technique of isolated pollen culture in the tobacco plant model (Nicotiana tabacum L.) enable the researcher to strictly control pollen development in both the gametophytic and sporophytic direction. The nutritional status of the immature pollen grain at a particular stage of development provides the trigger for its development into one of the two phases found in the alternation of generations undergone by higher plants. In particular, a hunger signal is responsible for the derepression of cell division activity and the start of embryogenesis. Pollen starvation can occur in isolated pollen cultures in sucrose-free media, in excised anthers and flowers, and, under specific growth conditions, during pollen development in vivo.

Abstract: Seed set after selfing in E. grandiflorum is often reduced relative to seed set after crossing; however, the compatibility patterns seen are not due to genes of major effect (i.e., S alleles). There is quantitative variation in the proportion of pollen tubes reaching the base of the style after both self- and cross-pollinations. Pollen tubes require between 24 and 72 hr to reach the ovary, but pollen tube growth ceases after 72 hr. When styles were removed from the ovaries 5 days after pollination, between 10 and 80% of the pollen tubes in the stigma had not reached the base of the style. The number of pollen tubes at the base of the style is a much better predictor of seed set than is the number of pollen tubes in the stigma. Pollen tube attrition is not affected by the age of the recipient flower or by the number of pollen donors contributing to the stigmatic pollen pool. The number of pollen tubes reaching the base of the style is dependent upon the source of the pollen and appears to be a decelerating function of the number of pollen tubes present in the stigma. SEED PRODUCTION in angiosperms depends upon a sequence of steps, including pollen transfer to the stigma, pollen germination and pollen tube growth, ovule fertilization and seed development, and finally seed maturation and dispersal. Attrition during each step determines the upper limit on the number of participants (i.e., gametes or zygotes) in subsequent processes, and variation in the number of gametes or embryos successfully passing a particular stage contributes to variation in the reproductive success of the sporophytes in

Abstract: Examination of the gut contents of adult Rhingia campestris reveals that there are considerable differences in the relative amounts of pollen and nectar ingested by individual insects. Pollen, a rich protein source, is required most by females, particularly during those stages of ovarial development when yolk deposition occurs. Nectar, which is mainly carbohydrate, is required in large amounts by males, and is also required by females before and after oogenesis. These results are discussed in relation to the likely nutritional needs of the flies, and it is suggested that similar feeding patterns may be found in a variety of other flower visiting insects. Finally, reference is made to the problems of making ecological assumptions about feeding behaviour on the basis of the morphological attributes of the mouthparts.

Abstract: Large plants of Aralia hispida present their pollen and nectar in hundreds of small flowers that open sequentially over 2-3 wk in a pattern of synchronized protandry that alternates male and female phases. The primary pollinators, bumble bees, are able to discover individual plants with elevated levels of either nectar or pollen, and to return to them more often than to less rewarding plants. Both pollen and nectar are presented gradually over time in such a way as to favor traplining behavior by the bees, with many, frequent visits. In controlled environments, lifetime sugar production per flower varies among plants, among umbel orders within plants, and between male and female phases of bloom within umbel orders; there are further interactions among these sources of variation, which complicate any consideration of differential male-phase vs. female-phase nectar production. After draining, floral nectar is rapidly replenished, rendering umbels attractive to bees again within 15 min. Pollen production per flower and pollen grain size vary among umbel orders, increasing toward the end of bloom; grain size (but not production) varies among plants as well. Given the high visitation rate by bees, the gradual presentation of pollen should result in more efficient pollen dispersal than simultaneous presentation would.

Abstract: Fossil chloranthoid androecia,Chloranthistemon endressii gen. et spec. nov. are described from the Upper Cretaceous (Upper Santonian or Lower Campanian) of Scania, southern Sweden. They are three-lobed and dorsiventrally flattened with all pollen sacs borne laterally and inclined toward the presumed adaxial surface. The central lobe bears two pairs of pollen sacs, the lateral lobes a single pair each. The morphology, anatomy and valvate dehiscence of the fossil androecia is very similar to that seen in extant species ofChloranthus andSarcandra, but the in situ pollen differs from that of all extantChloranthaceae in being spiraperturate. A single chloranthoid androecium from the Lower Cretaceous (Upper Albian) of Maryland, North America has a more generalized structure thanChloranthistemon endressii. It consists of three stamens that are fused at the base, and each stamen bears two pairs of oppositely positioned pollen sacs. Combined with anatomical information from recentChloranthus the Lower Cretaceous specimen suggests that the androecium in the living genus has arisen by fusion and other modifications of three separate stamens each with a normal complement of four pollen sacs. The structure of both the Upper and Lower Cretaceous androecia suggest that these fossilChloranthaceae were insectpollinated. Macrofossil evidence combined with information from dispersed pollen indicates that theChloranthaceae diversified early in angiosperm fossil history and were an important component of Mid-Cretaceous plant communities.

Abstract: The proportion of background pollen grains in the seed crops of two Pinus sylvestris seed orchards in Central Finland was estimated with the aid of multilocus allozyme markers. The orchards studied were more than 30 years old and in full pollen production. For the bulked seed crops of the seed orchard with southern clones the estimated average of background pollination over four years was 26%. There were statistically significant differences between years. No significant heterogeneity in the degree of background pollination between clones was found. Among single ramets there was significant heterogeneity in the estimated contamination rates, but the variation was not related to position in the orchard. For the seed orchard with northern clones the bulked seed crop was studied only for one year and the level of background pollination was found to be 33 %. These estimates are fairly high, but lower than for many other orchards. Background pollination at this level will cause losses in expected genetic gains...

Abstract: THE analysis of pollen from marine cores has produced continental palaeoclimate records which have been directly correlated with the oxygen isotope record of global ice volume and regional climate1–3. Here we tie the palaeoclimate of southern Europe to this global climate signal by reporting continuous pollen and δ18O records of a well-dated core in the Tyrrhenian Sea for the time span of 55–9 kyr BP. These records show a strong covariation between the marine δ18O reversed curve and a good terrestrial climate indicator, namely the pollen abundance of deciduous oak from the upland sub-humid Mediterranean forest of southern Italy and Sicily, which seems mainly constrained by moisture variation. The Artemisia and grass pollen abundances document the shift between continental semi-desert and oceanic steppe climates. Repetitive successions between 55 and 33 kyr BP of grass, oak, Artemisia and Abies pollen abundance peaks occur in locked phase with δ18O depletion events and indicate that regional vegetation cycles closely accompany deglacial pulses of global extent.

Abstract: On the basis of the results of seven years (1982–1988) of pollen and meteorological monitoring in the atmosphere of Perugia and Ascoli Piceno (central Italy) beginning of pollen season forecasts for Gramineae and Olea europaea L. are reported. The beginning of the pollen season for grass varied between May 2 nd and May 27th while for Olea it varied between May 26 th and June 23rd. By a statistical analysis of these data several significant correlations were found between the onset of the principal period of pollination and the air temperature in the preceding months and the number of «heat units» required to flower. Utilizing multiple regressions a predictive method of the beginning of pollen season for both the taxa is reported.

Abstract: Temps de germination d'un ensemble de grains de pollen chez Erythronium grandiflorum en fonction de la densite des grains etudies en relation avec la selection pendant la croissance du tube pollinique

Abstract: In the majority of monocarpic plant species there is an increase with plant size in the ratio of allocation of female function (seeds) to male function (flowers or pollen). A graphical model is presented that develops the general hypothesis that this may be due to fitness returns from the male function decreasing faster with increasing size than the returns from expenditure on the female function. Model and data are discussed with reference to the evolutionarily stable strategy-approach (E.S.S.) of Lloyd a Bawa (1984).

Abstract: The acetolysis method intreduced byGunnar Erdtman is still a very welcome and highly successful technique in palynology. However, acetolysis destroys all pollen material with the exception of sporopollenin that forms the outer pollen wall, the exine. Modern palynology in its application to plant systematics and phylogeny must consider all sporoderm characters, not only those of the exine. The neglect of the intine may distort some principal palynological aspects. This is illustrated by cases of total breakdown or gross modification of thin exine structures (e.g. inBeilschmiedia, Strelitzia) and by the clarification of apertures (e.g.,Polyalthia, Fissistigma, Calluna). In our view the investigation of both acetolysed and non-acetolysed pollen is obligatory for a well balanced view of pollen structure and function.

Abstract: Pollen was analyzed in 7 eastern Atlantic cores located between 37° and 9°N. The cores lie along a transect in the main trajectory of the northeast trade winds. The northern sector of the transect is close to source areas of pollen; whereas, the southern sector is distant (<2000 km) from the pollen source areas. Winds dominate in the transport of pollen from the northernmost part of the trade wind belt to the coring sites. Therefore, the pollen in the cores is a potential monitor of eolian transport. 18O and 14C based time control of the sediment sections made it possible to display the pollen data as influx records. After having estimated latitudinal shifts of the different pollen source areas, spatial and temporal variations in the pollen flux have been used to evaluate changes in the trade wind vigor.

Abstract: The gene frequency for parallel spindles (ps) was estimated from the frequency of plants producing 2n pollen in three cultivated groups: 2x Phureja (phu), 2x Stenotomum (stn), and 4x Andigena (adg), as well as in four related wild taxa: 2x Solanum brevicaule (brc), 2x S. sparsipilum (spl), 4x S. gourlayi (grl) and 4x S. gourlayi-S. infundibuliforme hybrids (grl-ifd). Plants with more than 1% large pollen were considered as 2n pollen producers. Observations of meiosis in a sample of 2n pollen-producing plants indicated that parallel spindles is the mechanism of 2n pollen formation. The number of plants with 2n pollen among the total examined was 228 plants (15.5%) of 1,473 in 2x spl, 31 (26.7%) of 116 in 2x brc, 92 (17.4%) of 528 in 2x stn, 665 (22.1%) of 3,008 in 2x phu, 731 (51.4%) of 1,421 in 4x adg, 591 (41.2%) of 1,436 in 4x grl, and 36 (64.3%) out of 56 in 4x grl-ifd. The ps gene frequencies assuming Hardy-Weinberg equilibrium were: 0.393 for 2x spl, 0.462 for 2x brc, 0.417 for 2x stn, 0.470 for 2x phu, 0.847 for 4x adg, 0.801 for 4x grl, and 0.895 for 4x grl-ifd. Twenty-five adg clones were randomly selected from a large population and were crossed with 2x clone W5295.7, which produces 2n pollen by parallel spindles (ps). The 4x progenies from 4x×2x crosses were used to determine the genotypes at the ps locus by screening 10–20 plants in each family for 2n pollen. Based on chromosome segregation at the ps locus, 9, 14, 1, and 1 clones were nulliplex, simplex, simplex or duplex, and duplex, respectively. The frequency of the ps gene in the adg population was estimated to be 0.825 and 0.815 for chromosome and chromatid segregation, respectively. The high frequencies of 2n pollen and the ps gene in cultivated 2x and 4x groups, and in wild taxa closely related to them, provide evidence for sexual polyploidization in the tuber-bearing Solanums.

Abstract: The characteristic Mesozoic pollen genus Eucommiidites is described from pollen organs and seeds recovered in Cretaceous strata of North America and Europe. The pollen organs are from the lowermost Upper Cretaceous (Cenomanian) of Texas and are referred to Erdtmanitheca texensis gen. et sp. nov. They are spherical heads, composed of numerous, densely crowded, radiating pollen sacs that contain abundant well-preserved pollen. Combined LM, SEM and TEM investigations show that the pollen grains each have a distinct distal colpus flanked by two lateral colpi in an equatorial position. Pollen wall ultrastructure is gymnospermous with a thick lamellate inner layer (endexine) and an outer layer (ektexine) composed of a granular inner part and a homogeneous outer part. The endexine is thickened in the region of the colpi. Small seeds from the Lower Cretaceous (upper Berriasian to Valanginian) of Bornholm, Denmark contain abundant Eucommiidites pollen in their micropyles. The seeds are referred to Erdtman...

Abstract: DNA-content of nuclei from pollen was determined using flow cytometry The pollen from diploid genotypes gave rise to a 1C- and a 2C-peak of identical size, representing the vegetative and the generative nuclei Pollen of the interspecific hybrid (L auratum×L henryi) presented only 2C- and 4C-peaks, while in the interspecific hybrids (LבEnchantment’×Lpumilum) 1C-, 2C- and 4C-peaks were distinguished The different C-levels, representing the DNA-contents of the generative and vegetative nuclei in G1 and G2 phase respectively, can be related to haploid and diploid pollen Results of a meiotic analysis, a number of crossing experiments and pollen measurements agreed with the outcome of the flow cytometric determinations The flow cytometry method enables the large scale screening of collections of genotypes for their potential of 2n-pollen production

Abstract: Airborne pollen concentrations, measured continuously with a volumetric method at two places in central Italy and in The Netherlands, are compared with respect to both their quantitative and seasonal aspects. Special attention was given to three taxa which occur in the two geographically distinct regions and are known to cause allergic sensitization: Alnus (alder), Poaceae (wild grasses), and Artemisia (mugwort). Averagely, total pollen concentrations are slightly higher in central Italy. The start and the main period in early spring of the season of Alnus pollen, which is more common in The Netherlands, is rather variable from year to year, in both regions correlated with the air temperature in the preceding months. Poaceae pollen, making up to 10 to 20% of the total annual pollen concentrations in both regions, has its start and main season in late spring about one month earlier in central Italy than in The Netherlands, strongly correlated with air temperatures in April and May. The main period...

Abstract: The Scrophulariaceae is a large family of primarily herbaceous plants, containing some members which are root parasites, while others are non-parasitic. The parasites are all within the subfamily Rhinanthoideae, while most of the nonparasites have been included in the Antirrhinoideae. The Orobanchaceae is a small family, all of whose members are root parasites. The two families are generally considered closely related, so much so, that several genera (Buchnera, Harveya, Hyobanche, and Lathraea) have been moved back and forth between the families. In this study, light microscopy, scanning electron microscopy, and transmission electron microscopy were used to examine the pollen of 57 taxa: members of the Orobanchaceae and Rhinanthoideae, and several members of the Antirrhinoideae for out group comparisons. The resulting data showed no clear differences between the pollen of the Orobanchaceae and that of the rhinanthoid Scrophulariaceae. The grains were typically isopolar, radially symmetrical, more...