Multiple Pollen Research Articles

The Holocene vegetational history of the Nigerian Sahel based on multiple pollen profiles

Four Holocene pollen diagrams are presented from interdune depressions in the Manga Grasslands (northeastern Nigeria near 13°N). These sequences are interpreted using modern pollen spectra, statistical analyses and groupings based on phytogeographical affinity (Long Distance, Sahelian, Sudanian, Guinean). The roles of climate change and anthropogenic activity in the vegetational history of the central part of Sahel are evaluated. Particular attention is given to the separation of regional (Manga Grasslands) from local (individual depressions) vegetation trends. Humid conditions in the early and mid-Holocene (from 10,000 to ca. 3300 yr B.P.) enabled the establishment of, and sustained, swamp forest vegetation in the interdune depressions. The main taxa ( Alchornea, Syzygium and Uapaca) have Guinean affinities. The surrounding dunefields consisted of open savanna with Sahelian and Sudanian (e.g., Combretaceae, Detarium) elements present. Drier conditions ca. 3300 yr B.P. produced abrupt changes in pollen stratigraphy and led to the establishment of the modern vegetation of the Manga Grasslands. Although occupied since at least 3700 yr B.P., there is little evidence of human activity in the pollen diagrams. The nomadic pastoralism practiced by the human occupants of the Manga Grasslands may be palynologically undetectable. Although the Holocene vegetational history of the Manga Grasslands appears to have been primarily controlled by climate, caution should be exercised before drawing climatic inferences from these pollen sequences. For the early and mid-Holocene differences of ca. 1000 years exist in the timing of vegetation changes between the individual depressions. While water levels in the depressions are likely to be coupled to climate, the vegetation response appears to be strongly influenced by local conditions (in particular variations in the depth of depressions and so the relative height of water table). In addition, the Guinean swamp forest vegetation of the early and mid-Holocene is unlikely to be representative of vegetation trends at this latitude, but rather developed extrazonally as a result of the particular topographic/hydrological conditions prevailing in the Manga Grasslands. The problems of lags between climate and vegetation change and the presence of extrazonal vegetation, experienced in the Manga Grasslands, are likely to be common to other Sahelian pollen sites. The palynological information presently available for this zone is deemed insufficient for detailed subcontinental scale reconstructions of vegetation and climate to be attempted.

Factors influencing male mating success in bur oak, Quercus macrocarpa.

Pollen donors of acorns and saplings in a stand of bur oak were identified by paternity exclusion using microsatellite genotype analysis. Here we examine the influence of several factors likely to affect reproductive success of males with wind-dispersed pollen, including distance of pollen donor from maternal tree, genetic relatedness of pollen donor to maternal tree, direction of pollen donor relative to maternal tree, and size of pollen donor (crown volume and trunk diameter). Surprisingly, none of these factors were strongly correlated with fertilization success, although weak but significant correlations with crown volume and distance were found. The slight influence of distance is actually overestimated here, because our analysis necessarily excluded a large proportion of pollinations that were effected by trees outside the stand. The pollen donors outside the stand were not identified, but were more than 150 meters away. Pollination patterns in this stand of bur oak are quite complicated. Seed parents were fertilized by multiple pollen donors within the stand from all directions and as far as 200 m away. These results caution against the use of models of pollination that are based on simple distance or directional parameters because they will not adequately predict gene flow or male reproductive success. Our results further emphasize the importance of genetically identifying successful pollen donors rather than relying on patterns of physical movement of pollen.

Early Ironworking and its Impact on the Environment: Palaeoecological Evidence from Bryn y Castell Hillfort, Snowdonia, North Wales

The environmental impact of the Late Iron Age and Romano-British ironworking hillfort of Bryn y Castell in upland southern Snowdonia was investigated by multiple profile pollen and charcoal analysis of nearby valley mire and blanket peat deposits. Pollen data, collected from five radiocarbon dated profiles within a 1.5 km radius of the hillfort, indicate that ironworking activities apparently had only localised impact on the environment. Small-scale declines in certain arboreal taxa can be correlated with occupancy of the site. Betula and Alnus appear to be most affected, with minor loss of Corylus and Quercus. The pattern of arboreal taxa and charcoal values during the ironworking period is considered in the context of evidence for deliberate woodland management, the scale and duration of ironworking, and alternative forms of human disturbance. Overall, the results of the pollen analysis suggest that woodland recovered to its pre-ironworking level except in the immediate vicinity of the hillfort. Integration of the archaeological and palaeoecological data allowed understanding of the resource-based aspects of this prehistoric industrial site and the results have wider implications for the field of experimental industrial archaeology.

In vitro micropylar penetration of the pollen tube in the ovule of Gasteria verrucosa (Mill.) H. Duval and Lilium longiflorum Thunb.: conditions, attraction and application

Freshly isolated ovules of Gasteria verrucosa and Lilium longiflorum, maintained on agar medium, were used to monitor micropylar penetration of pollen tubes. In Gasteria, the percentage of in vitro micropylar penetrations is comparable with the penetration percentage in vivo. The penetration efficiency was related to the season, stage of flower development and method of emasculation. Micropylar penetration in vitro is independent of the orientation of the micropyle. Multiple pollen tube penetration occurs as in vivo, and pollen tubes show a preference for micropyles with micropylar exudate. All these observations indicate that an attractant is present in this exudate. After washing the ovules with different solvents before in vitro pollination, the penetration percentage can be influenced. Washing with solvents affecting proteins remarkably influences the rate of penetration, suggesting that the possible attractant has a proteinaceous component. Incompatible as well as interspecific and intergeneric pollinations, both for Gasteria and Lilium, were applied and resulted in micropylar penetration. The observed penetration of Gasteria pollen tubes in the micropyle of Lilium ovules points to a non-specific micropylar attraction.

Structural aspects of in vitro pollen tube growth and micropylar penetration inGasteria verrucosa (Mill.) H. Duval andLilium longiflorum Thunb.

In vitro penetration of the micropyle of freshly isolatedGasteria verrucosa ovules by pollen tube was monitored on agar medium. 40–60% of the micropyles were penetrated, comparable with in vivo penetration percentages. When germinated on agar,Gasteria pollen tube elongation lasts for up to 8 h while plasma streaming continues for about 20–24 h. The generative cell divides between 7 and 20 h after germination, and after 20 h the pollen tube arrives at one of the synergids. The sperm cells arrive after 22 h. The whole process takes more time in vitro than in vivo. In fast growing pollen tubes, a pulsed telescope-like growth pattern of tube elongation is observed. The formation of pollen tube wall material precedes tube elongation and probably prevents regular enlargement of the pollen tube tip-zone. Rapid stretching of the new pollen tube wall material follows, probably due to gradually increased osmotic pressure and the use of lateral wall material below the tip. The stretching ceases when the supplies of plasma membrane and excretable wall material are exhausted. Multiple pollen tube penetration of the micropyle occurs in vitro as it does in vivo. Most pollen tube growth ceases within the micropyle but, if it continues, the pollen tubes curl. Inside the micropyle the pollen tube shows haustorial growth. At the ultrastructural level, the wall thickening of in vitro pollen tubes is quite similar to that in vivo. Before transfer of pollen tube cytoplasm a small tube penetrates one of the synergids. Sperm nuclei with condensed chromatin are observed in the pollen tube and the synergid. In vivo prometaphase nuclei are found in the most chalazal part of a synergid, against the egg cell nucleus and nucleus of the central cell at a later stage. Using media forLilium ovule culture,Gasteria ovules were kept alive for at least 6 weeks. Swelling of the ovule depends on pollen tube penetration. The conditions for fertilization to occur after in vitro ovular pollination seem to be present.

Systemic reactions occurring during immunotherapy with standardized pollen extracts

Specific immunotherapy with standardized extracts administered by a rush protocol can induce systemic reactions (SRs). A prospective study was conducted in 454 pollen-allergic patients (aged 5 to 62 years) (1) to compare the incidence of SRs during a 3-day rush or step protocol, (2) to determine if patients presenting pollen asthma or those allergic to multiple pollen species would have an increased incidence of SRs, and (3) to attempt to decrease SRs. According to their sensitivity, patients received standardized extracts of orchard grass, andlor Parietaria, and/or olive, andlor plane-tree pollen with the same allergenically bioequivalent maintenance dose. Patients 10 years of age and older received 2000 BU; patients younger than 10 years, 1000 BU. The occurrence of SRs was carefully monitored. The incidence of SRs per patient ranged from 2.6% to 31.1%. With the rush protocol, there was a significant decrease in SRs after premedication ( p < 0.015). Severe SRs decreased further when the increase in doses was stopped because large local reactions occurred. Step protocol was only slightly better tolerated than rush protocol. Bronchial adverse reactions occurred more often in patients presenting asthma during previous pollen seasons. No reaction started 45 minutes or later after the last injection.

Pollen Viability and Vigor in Hybrid Southern Highbush Blueberries (Vaccinium corymbosum L. ×spp.)

Pollen from six southern highbush blueberry cultivars derived from Vaccinium corymbosum L. and one or more other species (V. darrowi Camp, V. ashei Reade, and V. angustifolium Aiton) was incubated on nutrient agar to determine tetrad viability, pollen tube growth rates, and incidence of multiple pollen tube germinations. `Avonblue' pollen had a significantly lower tetrad germination percentage than `Georgiagem', `Flordablue', `Sharpblue', `Gulfcoast', or `O'Neal', all of which had &gt;90% viable tetrads. The in vitro growth rate of `O'Neal' pollen tubes was significantly higher than the growth rates of `Sharpblue' and `Georgiagem pollen tubes. Of those tetrads that were viable, more than two pollen tubes germinated from 83% and 91% of the `Gulfcoast' and `Sharpblue' tetrads, respectively, while only 11% of the `Flordablue' tetrads produced more than two pollen tubes. The total number of pollen tubes germinated per 100 tetrads ranged from 157 (`Flordablue') to 324 (`Sharpblue'), resulting in actual pollen grain viabilities ranging from 39% to 81%. Genetic differences in pollen vigor, as indicated by pollen viability, pollen tube growth rates, and multiple pollen tube germinations, may influence blueberry growers' success in optimizing the beneficial effects of cross-pollination on fruit development.

Clinical and immunologic reactivity of patients allergic to grass pollens and to multiple pollen species: I. Clinical and immunologic characteristics

The heterogeneity of pollen-allergic individuals is well-known but poorly characterized. Twenty-six patients were studied to characterize their immunologic and clinical patterns. Thirteen patients were allergic only to grass pollens, and 13 other patients were allergic to grass-pollen and other pollen species, including Cupressaceae, plane tree, olive, and Parietaria. The IgE response was assessed by the titration of serum total IgE and orchard grass-specific IgE, as well as by IgE immunoblots to orchard-grass pollens. Clinical reactivity was assessed by nasal challenge with orchard-grass pollens before the pollen season and nasal and bronchial symptom-medication scores between April 1 and June 15. Pollen counts were obtained during this period of survey. Polysensitized patients had significantly increased levels of serum total and specific IgE and a greater heterogeneity of IgE immunoblots, suggesting an enhanced qualitative and quantitative IgE immune response. Polysensitized patients had nasal and bronchial symptoms occurring earlier than grass pollen-allergic individuals, confirming the priming effect caused by other plans flowering with an earlier season for both nasal and bronchial mucosa. Alternatively, the early symptoms may be attributable to the tree pollens or might reflect the higher grass-pollen IgE level in the polysensitized group. Bronchial symptoms appeared a few weeks after nasal symptoms. Nasal challenges were similar in both groups, and the severity of nasal symptoms during the season was not significantly different in both groups, suggesting that the intensity of symptoms is not related to the sensitization nor to the IgE immune response of the subjects.

236 Clinical and immunologic reactivity of patients sensitive to grass and multiple pollens

236 Clinical and immunologic reactivity of patients sensitive to grass and multiple pollens

EVALUATION OF MENTOR POLLINATION FOR BLUEBERRY BREEDING

Two clones of anthocyanin-deficient (AD) Vaccinium elliottii (2×, homozygous recessive, yy) were used as seed parents in experiments combining normal and AD pollen. AD gives a seedling marker to distinguish the pollen parent. In the first experiment, flowers were pollinated daily for one, two, three or four days. AD and normal V. elliottii pollen were applied on separate days. The last day of each treatment received the opposite genotype from the previous day(s). The first pollination gave as many, or more, seedlings as later applications but the number of seeds per fruit was higher with multiple pollen applications. The second experiment used pollen from normal V. corymbosum (4×) alone or mixed with AD pollen from the 2× clones. Results depended on the seed-parent genotype. There was no difference between treatments in the number of hybrids produced by W81-1, which tends to set fruit even with only one seed per berry. Only mixed pollen yielded hybrids from clone FL83-139, which was never observed to produce berries with only one seed; apparently the mentor AD pollen helps to set the fruit, thereby allowing the rare hybrid seeds to develop.

Early Flandrian Vegetational Development on the Coastal Plain of North Ayrshire, Scotland: Evidence from Multiple Pollen Profiles

Early Flandrian Vegetational Development on the Coastal Plain of North Ayrshire, Scotland: Evidence from Multiple Pollen Profiles

374 Efficacy of rush immunotherapy with grass or multiple pollen species assessed by nasal challenge

374 Efficacy of rush immunotherapy with grass or multiple pollen species assessed by nasal challenge

Are “multiple Cross-multiple pollen hybrids” an answer for productive populations in Brassica campestris var. ‘brown sarson’?

Results on 167 f1 'mucromphs' reported earlier were re-examined with the view of determining the potential of component characters in correct identification of parental gca status and F1 heterosis. It was found that a judicious combination of 'plant' and 'ratio' characters would be of direct usefulness in assessing population performance. The role of seedling characters in the process of making a desired level of multiple cross was illustrated. It was found that H X L mucromphs could provide a broad genetic base which has a higher probability of getting channelised into productive populations. It was concluded that 'multiple cross-multiple pollen hybrids' can provide a feasible solution for breeding productive composite populations in Brassica campestris.

Are ?multiple cross-multiple pollen hybrids? an answer for productive populations in Brassica campestris var. ?brown sarson??

A set of complex crosses with multiple crosses as female parents were made using multiple pollen in turnip rape (Brassica campestris L.). These multiple cross - multiple pollen hybrids (mucromphs) were evaluated for a large number of quantitative characters including yield. New methods were proposed to study such genetic material in depth so as to formulate suitable strategies to breed for attractive seed yield.

INVESTIGATIONS OF ANGIOSPERMS FROM THE EOCENE OF NORTH AMERICA: A MIMOSOID INFLORESCENCE

Six examples of a spicate inflorescence from the Middle Eocene Claiborne Formation in western Tennessee have been investigated. Individual flowers are small, alternately arranged, nearly sessile, and perfect. The style protrudes 2 mm beyond the floral envelope and terminates in a slightly swollen, rounded stigma. Both the style and the stigma are hairy. Ten stamens are exserted and extend 5 mm beyond the floral envelope. Anthers are small, versatile, and dehisce longitudinally. Pollen grains are tricolporate, tectate, and are in permanent tetrahedral tetrads 32 μm in diameter. Comparison of the fossil inflorescences with those of extant families having multiple pollen grain configurations suggests that the fossil inflorescences are most closely allied to the subfamily Mimosoideae of the Leguminosae. These are the first structurally documented remains of the Mimosoideae from the Middle Eocene.

Immunologic studies of repository ragweed pollen therapy

T has been shown that after multiple injection therapy with pollen extracts, a thermostabile blocking antibody is produced.’ There is usually no change in the skin-sensitizing antibody titer during hyposensitization therapy, but one investigator2 reported a temporary early increase in this antibody response. More recently, we3 and others 4s 5 have shown that there is an increase in the hemagglutinating antibody titer followin g multiple aqueous pollen injection therapy as measured by either the tanned cell or bis-diazotized benzidine technique. Unfortunately, neither the significance of this antigenic response nor the apparent lack of correlation between the change in blocking, skin-sensitizing, or hemagglutinating antibodies to each other, or to the clinical response of the patients is, as yet, explained. Repository pollen therapy has been reported by several investigators to be at least as effective in the relief of pollinosis as the conventional multiple injection therapy. Nevertheless, there has been a paucity of information on the immunologic response following pollen emulsion therapy. However, Lovelessfi noted that blocking antibody titers were increased and sustained by repository therapy. In view of these facts, it was decided to critically study this phase by means of determining the change in blocking, reagin, and hemagglutination antibody titers in patients who received either the repository pollen, a placebo emulsion, or the -usual multiple aqueous injection therapy.