Abstract: Initial seed set and fruit set were pollen-limited in a Costa Rican population of Passiflora vitifolia, a self-incompatible species with 200–350 ovules per flower. Pollination intensity was measured by counting the number of allogamous pollen grains on stigmas of the large one-day flowers. Hand-pollinations demonstrated that 25–50 pollen grains are required for fruit set, and >450 are needed for maximum seed set, with a pollen:seed ratio of about 1.6:1.0. Hummingbirds (Phaethornis superciliosus) delivered sufficient allogamous pollen for maximum seed set to only 28% of the flowers examined. Naturally pollinated flowers yielded fewer fruits and fewer seeds per fruit than those pollinated by hand. Most pollen transferred by humming-birds was self-incompatible; emasculated flowers yielded higher seed set than flowers with intact anthers. Visitation rates did not provide a good index of effective pollination. There were significant differences in ovule number, maximum seed set, and maximum per cent seed set among individual vines. More than half of an individual's flowers failed to set fruit, whether pollinated by birds or by hand. In this population, maximum reproductive potential may be limited by maternal resources for fruit development, but seed set varies with pollination intensity. Pollen-limited seed set may be a disadvantage of self-incompatibility, especially in species with many-seeded fruits.

Abstract: A 403—cm core was recovered from Hanging Lake in unglaciated northern Yukon. Twenty—one radiocarbon dates indicate that the section is at least 25 000 and possibly 33 000 yr old; they permit the calculation of pollen influxes for the full—glacial in eastern Beringia. Numerical methods were used to divide the pollen stratigraphy into five zones. From prior to 33 000 to 18 450 BP, a herb zone was dominant (zone HL 1) with high percentages of Gramineae, Artemisia, and Cruciferae. However, the low pollen influx, ranging from 5—100 grains°cm—2°yr—1, the low organic content of the sediment, and the occurrence of open—ground taxa all indicate that the vegetation cover was sparser than it is today. The arctic—alpine affinities of the herb pollen show that generically the vegetation was akin to modern arctic plant communities. Modern fellfield communities in the northern Yukon and Siberia have a rich and endemic Artemisia flora and they can produce pollen spectra comparable to that of the herb zone. Percent and influx values for spruce, alder, and birch increased slightly during subzone H 1B (21 680—18 450 BP); this subzone probably represents an interstadial. From 18 450 to 14 600 BP, a Salix—Cyperaceae zone (HL 2) occurred, suggesting the development of snowbed and willow scrub communities in sheltered areas. Between 14 600 and 11 100 BP Betula pollen dominated (zone HL 3) indicating the spread of dwarf birches, but the influx data show that this initial increase was modest compared with the subsequent zone and thus dwarf birches were probably restricted at this time to more favorable habitats. The spread of birch together with the increased total pollen influx, the higher organic content of the sediment, and the increased richness of herb pollen indicates that the local flora was more diverse and that the vegetative cover increased. The climate must have warmed. Zone HL 4 (Ericales zone) spanned the period from 11 100 to 8900 BP. Wet heath communities became locally abundant, poplar was more abundant at the beginning of this zone than at any subsequent time, the ranges of Typha latifolia and Myrica gale were greater than today, and pollen influx and sedimentation rate both increased greatly. Spruce became regionally abundant. These varied changes are probably in response to a warmer and wetter climate; they provide evidence for a late Pleistocene to early Holocene warm interval initially recognized by McCulloch and Hopkins (1966). Zone HL 5 (Alnus crispa zone) has been dated from 8900 BP to the present; it reflects the regional expansion of Alnus crispa on organic soils.

Abstract: Summary When pollen from Hieracium floribundum Wimmer and Grab. (Compositae) was applied to stigmas of Diervilla lonicera Mill. (Caprifoliaceae) in mixtures with Diervilla pollen, Diervilla fecundity was strongly depressed. While this phenomenon is unlikely to be of importance to Diervilla under field conditions, this property of Hieracium pollen may have stronger effects on other ecological associates. The only other reported instance of inhibitory pollen is from Parthenium hysterophorus L., which, like Hieracium, has allelopathic properties.

Abstract: Analysis of 90 samples from coastal and continental shelf areas off eastern Canada between 42 and 69°N shows that Quaternary pollen and spores are present in recent marine muds throughout this regi...

Abstract: Pollen grains were harvested from an interspecific F1 hybrid between the cultivated tomato, Lycopersicon esculentum Mill., and its wild relative Lycopersicon hirsutum Humb. & Bonpl., a low temperature tolerant accession originating from an altitude of 3200 m in the Peruvian Andes. The two species differ for electrophoretically-detectable loci that mark six (possibly seven) of the 12 tomato chromosomes. Isozyme analysis of the BC1 populations derived from controlled pollinations at normal and low temperatures indicates a significant skewing of allelic frequencies favoring two independent chromosome segments of L. hirsutum at low temperatures. The results demonstrate that gametophytic selection for low temperature tolerance of tomato pollen is determined, at least in part, by genes expressed in the haploid pollen.

Abstract: The production of large numbers of haploid plants from pollen grains in aseptic culture of anthers or isolated pollen grains has now been demonstrated in many angiosperms. It is a technique which holds much promise for creating desired variability by mutations for biochemical and applied genetics and for producing pure lines for crop improvement. This paper reviews the research on the production of haploids from pollen grains. The response is dependent on a variety of factors such as media formulation (especially the hormone component), genotype and physiological status of the donor plant, developmental stage of the pollen grain, anther culture environment and anther wall itself-all of which influence greatly the successful production of haploid plants. Although still in its infancy, the culture of isolated pollen is seen as a promising line of further research as it has the potential of offering several advantages over the culture of whole anthers.

Abstract: The application of abscisic acid solution to developing spikes of wheat (cv. Gabo) via wicks threaded through peduncles at the stage of meiosis in pollen mother cells caused pollen sterility without affecting female fertility. The concentration of abscisic acid measured in the spikelets of plants treated in this manner was close to that induced by water stress, which produced a similar level of pollen sterility. After pollen mother cell meiosis, treatment with abscisic acid had no effect on pollen fertility, as has been shown previously with water stress. Abscisic acid applied immediately before meiosis reduced fertility, in contrast to the effect of water stress, but this may have been due to persistence of the hormone in the plant. High temperature during pollen mother cell meiosis had no effect on the endogenous abscisic acid content of the spikelets, even where the treatment caused a complete inhibition of grain set.

Abstract: (1982). Classopollis pollen as an indicator of Jurassic and Cretaceous climate. International Geology Review: Vol. 24, No. 10, pp. 1190-1196.

Abstract: Analyses of lignin oxidation products and pollen for an 11-meter core from Lake Washington provide independent but similar reconstructions of the late Quaternary vegetation in the Puget Lowland. An exception is in sediments of the late Pleistocene where pollen percentages and influx values suggest conifer forest whereas lignin compositions suggest a treeless source region. This dissimilarity appears to result from different major provenances: eolian transport of pollen to the lake from adjacent or downstream drainage basins as opposed to fluvial transport of lignified plant debris only from the Lake Washington drainage basin.

Abstract: The arctic-steppe concept is tested by scrutiny of two detailed late Pleistocene herb-zone pollen records from Hanging Lake (tundra) and Lateral Pond (woodland) in northern Yukon Territory and by consideration of other published pollen sequences in eastern Beringia. In particular, we examine the idea that Alaska and northern Yukon, when joined to Siberia by the Bering land bridge, “constituted the eastern end of a huge grassland biome, unequaled today in size and character.” Herb-zone pollen spectra consist largely of taxa whose modern affinities are arctic-alpine. Contrary to expectations of the arctic-steppe concept, herb-zone spectra do not show diversity of pollen taxa higher than in the modern pollen rain. Pollen influx rates are as low or lower than during the Holocene at the same sites and an order of magnitude lower than in modern central Canadian prairies. Influx rates for Artemisia, as well as for most of the other prominent herbs and grasses, are about the same in the herb zone as in younger pond sediments, although herb-zone taxa form much smaller percentages of the total pollen rain after birch, alder, and spruce appear in younger sediments. Pleistocene pollen spectra from western Europe are interpreted as representing open, discontinuous tundra or polar desert severely affected by frost action. The eastern Beringian herb zone also probably records discontinuous tundra vegetation floristically and physiognomically similar to communities found in eastern Beringia today on xeric, regosolic sites above the montane or beyond the arctic treeline. The communities represented by the herb zones are not extinct but are restricted in distribution now due to competition by species adapted to the more leached and humic Holocene soils and species that have immigrated or expanded in response to climatic amelioration. We conclude that the “arctic steppe biome” never existed in eastern Beringia during the late Quaternary. The large and diverse ungulate populations probably were present during Pleistocene interstadials more than 30,000 years ago–intervals for which we lack adequate palynological records–rather than during the time of the herb zone, 30,000 to 14,000 years ago. It is doubtful that herb-zone vegetation could support a large and diverse population. Termination of the herb zone by the dwarf brich “rise” about 14,000 years ago signals a climatic amelioration (warmer and wetter). It is unlikely that the spread of this more productive vegetation was a factor in late Pleistocene mammalian extinctions.

Abstract: A high gene frequency for ps (parallel spindles) is expected in cultivated tetraploid potatoes, S. tuberosum Group Tuberosum, if 2n pollen produced by ancestral diploid plants which were psps was involved in the origin and evolution of the potato. Fifty-six North American cultivars (varieties and advanced selections) were pollinated by diploid clones, either W 5295.7 or W 5337.3 which are homozygous recessive for ps. The segregation ratios in regard to 2n pollen production in derived tetraploid progenies, from 4x×2x crosses, reveal the genotype of ps in the cultivars. Microsporogenesis of 2n pollen producing 4x progeny was observed to avoid an overestimation of the frequency of 2n pollen producing plants due to mechanisms other than parallel spindles. More than 50% of the 56 cultivars are simplex (Pspspsps), since in each of these cultivars about 50% of their progeny produced 2n pollen. The ps gene frequency in the 56 cultivars was estimated as high as 0.69. The high frequency of ps in the tetraploid cultivars clearly supports the hypothesis that 2n pollen produced by plants homozygous recessive for ps have been involved in the origin of cultivated tetraploid potatoes, since a higher frequency of ps in the tetraploid than in the ancestral diploid population can be expected from sexual polyploidization but not from somatic doubling. The importance of meiotic mutants such as ps for the successful evolution of polysomic polyploids is emphasized.

Abstract: Pollen of Petunia hybrida was germinated in artificial medium. At the beginning of the incubation, a large amount of proline, which comprises about half of the total free amino acid pool, was released into the medium. Part of this proline is reutilized by the pollen. Uptake of radioactive amino acids and their incorporation into proteins were studied. The highest rate of protein synthesis was found directly after the onset of germination. The endogenous free proline pool was found to be compartmentalized; one of the compartments is the protein precursor pool; its size is probably much less than 50% of the total free proline in the pollen.

Abstract: Late middle Eocene to early late Eocene spores and pollen from the Werillup Formation in the Bremer Basin of Western Australia are diverse, generally abundant, and well preserved. The assemblage from the Fitzgerald River area is strikingly similar to assemblages of comparable age from southeastern Australia, to which it is correlated on the co‐occurrence of several stratigraphically restricted species. Moreover, a significant number of species, previously known only from southern and southeastern Australia, are recorded for the first time in Western Australia and thirteen new species are described. These are Clavatipollenites glarius, Liliacidites phormoides, Proteacidites bremerensis, P. cumulus, P. rugulatus, P. rynthius, P. scitus, Propylipollis tegillis, Tetracolpo‐rites palynius, Tricolporiles adelaidensis, Triporopollenites apiculatus, T. delicalus and T. vargus.

Abstract: The inheritance of 2n pollen formation was studied in two diploid clones of alfalfa, Medicago sativa L. The two clones consistently produced a high frequency of 2n pollen, and they also porduced good seed set when used as males in 4x-2x crosses due to the functioning of 2n(2x) pollen. For the inheritance study the two clones were crossed with diploid clones of cultivated alfalfa at the diploid level (CADL), and with several clones of diploid M. falcata. In segregating families, plants that produced a high frequency of 2n pollen were identified by good seed set when used as males in 4x-2x crosses, and/or by bimodal pollen sizes. Plants that produced 4% or more 2n pollen generally produced greater than one seed per pollination in 4x-2x crosses, and these plants were considered 2n pollen producers. Analysis of self, F1, F2 and backcross (BC) families indicated 2n pollen formation was controlled by a single recessive gene, designated rp (restitution pollen). An allelism test indicated 2n pollen formation was ...

Abstract: Gene flow in an experimental garden of Cucumis melo (Cucurbitaceae), the cultivated muskmelon, was measured by placing plants carrying a dominant gene (green cotyledons) in the center of an 18 x 18-m field of recessive plants (yellow cotyledons). At the end of the growing season, all fruits were collected, and seeds planted for analysis of the progeny. The 123 fruits yielded 41,875 seedlings whose genotypes were recorded. Gene flow decreased with increasing distance from the central plot, while the variance increased. The decrease in frequency of the green gene did not follow a leptokurtic pattern over the distance measured, and there was a marked asymmetric and patchy pattern of gene flow in the field. The directionality contributed to a bimodal pattern of gene frequencies among fruits at the edges of the field, some fruits with no green seedlings, some with many. Bumblebee movements were recorded during 4,296 flower visits in an identically arrayed melon field. Bees usually moved to very nearby plants and visited only a few flowers on any one plant. This suggests that pollen carryover from the central patch out was quite high in the test garden. These findings show that local gene flow patterns in plant populations may be complex, and do not always follow regular and symmetrical models. The complex arrangement of progeny genotypes, when acted upon by local selective forces, may contribute to small-scale differences often seen in plant populations. RECENT PROGRESS on the ecological genetics of plant populations has concentrated on demographic processes and gene flow dynamics. Several studies have shown that the structure of plant populations often includes small scale differences in genotypes (Schaal and Levin, 1976-; Raven, 1976); gene flow dynamics apparently contributes to this pattern. With mechanisms for measuring the morphological and biochemical variation in nature now widely available, the role of gene flow in maintaining and creating the variation needs clarification. For plants, gene flow is mediated by seed and pollen dispersal. Studies of seed movement and germination (Harper, 1977, chapters 2-5) and of pollen movement (Levin and Kerster, 1974) generally show restricted patterns that vary with the type of disperser and the 1 Received for publication 11 July 1981; revision accepted 30 June 1982. I thank Jan Roueche for dedicated and expert help in maintaining the plots and analyzing the data. Helga Cohen and Judy Mishkin played major roles in collecting and analyzing data. Seed stocks for this work were supplied by Dr. Perry Nugent of the U.S. Department of Agriculture Vegetable Breeding Laboratory, Charleston, S.C. This work was funded by N.S.F. Grants DEB 78-24992 and 7927022, and funds from the Southern Regional Educational Board. Experimental work was done at the Clemson University Sandhill Experimental Station, Pontiac, S.C. and the University of South Carolina Department of Biology; I thank both institutions for use of facilities. J. Mishkin, J. R. Powell, R. G. Harrison, K. K. Kidd and this journal's reviewers made helpful suggestions, for which I am grateful. morphology of the seed and pollen grain. Much work on estimating pollen flow is based on detailed observations of pollinator movements, which assumes a close correlation between these movements and pollen transferred among flowers. This procedure has contributed much to the theory of plant microevolution, such as the role of density-dependent population structure in altering gene flow patterns (Levin and Kerster, 1969). However the correlation is difficult to generalize among vectors (Primack and Silander, 1975; Levin, 1981), and may not always be accurate. Actual gene flow has been measured in several agronomic studies where interest has been in minimum distance needed to isolate cultivars. In these studies, crop strains with genetic markers are interplanted in geometric arrays, natural pollination occurs, then the F1 is searched for the marker phenotypes (e.g., Crane and Mather, 1943; Bateman, 1947a; Griffiths, 1950). Few such studies on actual gene flow have been done in natural populations because the existence of large monomorphic patches within a population of contrasting phenotypes is rarely found in nature. Consequently, studies in experimental gardens are of particular interest in understanding microevolutionary processes in plant populations. This study uses the technique of growing plants in a test garden that are homozygous for different alleles at one locus that controls a morphological trait. The microdistribution of

Abstract: ヒラズハナアザミウマの飼育法を検討した結果,以下のことが明らかとなった。1) ヒラズハナアザミウマは薄膜(シーロンフィルム)を通して液体飼料を吸汁でき,この薄膜を通して液中によく産卵することがわかった。2) ヒラズハナアザミウマは,蜂蜜液だけでは発育,産卵できなかったが,チャ,ナシ,イチゴ,チューリップ,マツなどの花粉と蜂蜜液の組み合わせでは,餌を交換しなくても幼虫が発育し,85∼90%の高率で羽化成虫を得ることができた。さらに,この方法により産卵も促進した。3) ハナアザミウマも花粉と蜂蜜液で飼育できることがわかり,訪花性アザミウマ類の簡易大量飼育の可能性が示唆された。4) 本法による発育調査の結果,ヒラズハナアザミウマ,ハナアザミウマとも,羽化までの発育は揃い,成虫の生存期間は長く,産卵数は極めて多いことがわかり,訪花性アザミウマ類にとって,本飼育法は,葉や果実を用いる飼育よりも本来の餌条件に適合していることがわかった。

Abstract: Deteriorated pollen grains have been recorded from Flandrian sediments in three sites near Callander in Perthshire, and diagrams are presented of deteriorated pollen as opposed to the overall pollen totals discussed in the previous paper. The problems of interpreting records of deteriorated pollen are discussed, a format for pollen diagrams conveying detailed information on deteriorated grains is introduced, and the palaeoenvironmental implications of the records are considered. It is shown that major changes in deteriorated pollen totals are common to all three diagrams, with low percentages in the early Flandrian, and pronounced increases in deteriorated totals coincident with the Corylus decline at each site. It is suggested that similar studies at other sites in northern Britain may prove these trends to be consistent features of Flandrian pollen diagrams.