High Pollen Production Research Articles

The Importance of Flowering Time and Flower Number in the Relative Fitness of Males and Hermaphrodites in Datisca glomerata (Datiscaceae)

Abstract The persistence of male plants in androdioecious populations of Datisca glomerata requires a large theoretical increase in male fertility of male plants over hermaphrodites. Recent studies have supplied evidence that high outcrossing rates, inbreeding depression, and high male pollen production per flower contribute to increased male fitness in this species. We tested for the contribution of increased flower number and early flowering to a male fitness advantage. Flower number was not found to differ significantly among male and hermaphrodite siblings, but males flowered significantly earlier. Flowering time was influenced also by population and family of origin.

Effects of supplemental mass pollination (SMP) in a young and a mature seed orchard of Pinus sylvestris

The effects of supplemental mass pollination (SMP) were studied in two Pinus sylvestris seed orchards differing in pollen production. Pollen was dusted over the whole tree during the period of peak female receptivity using a pressurized backpack sprayer. The success of SMP was assessed by means of allozyme markers. In the orchard with high pollen production, detectable differences in SMP success rate were found between clones, but the success rate was not influenced by the number of pollinations per day. The average estimated success rate of SMP was 19%. In the orchard with low pollen production, no significant differences in SMP success rate were found between years (22 versus 34%) or between clones. The SMP success rate in the low pollen production orchard varied between 14 and 69%.

Airborne pollen and spores monitoring in Buenos Aires city: A preliminary report. Part II. Herbs, weeds (NAP) and spores. General discussion

The herds and weeds pollen (NAP) and spores of Buenos Aires city were collected using a Tauber trap from July 1989 to June 1990. A high NAP pollen production period was found from October to March, reaching an annual peak in October. The NAP fraction is dominated by Compositae, Poaceae, Cyperaceae and Chenopodiaceae/Amaranthoideae. Spores are scarce along the year and they are mainly represented by Bryophytes. From the comparison of trees and shrubs pollen content (AP), NAP and Spores fractions, three aeropalynological seasons could be described: An AP Season with dominance of trees and shrubs, from July to October; a NAP Season with dominance of herbs and weeds, from November to April, and a Spore Season from May to June.

Pollen Production in the Androdioecious Datisca glomerata (Datiscaceae): Implications for Breeding System Equilibrium

Abstract Androdioecy (the presence of males and hermaphrodites in a breeding population) is a rare reproductive system in plants, with Datisca glomerata (Datiscaceae) representing the only well‐documented example. Recent reports of high outcrossing rates, inbreeding depression, and high male pollen production satisfy theoretical predictions for the continued maintenance of androdioecy in populations of this species. However, in prior studies pollen production was measured indirectly in terms of numbers of anthers per flower—based on the assumption that male and hermaphroditic plant have equal numbers of flowers and that anthers from the two sexual morphs produce equivalent amounts of pollen. Herein, we demonstrate that male and hermaphrodite plants do not differ significantly in terms of flower number, but that pollen production in anthers from hermaphroditic plants is 12.6% higher than in anthers from male plants, thus refining the estimate of relative pollen fecundity of male versus hermaphrodite plants. The differential lowers the frequency of males predicted by theory, but is still consistent with the maintenance of androdioecy in this species.

The Cistaceae as food resources for honey bees in SW Spain

SUMMARYThe presence of Cistaceae pollen in honey and pollen samples from different localities of this area was determined. In addition, pollen from Cistaceae species collected throughout 1986 by two honey bee colonies placed near Hinojos was studied. Observations were also made on the presence of Cistaceae pollen in honey produced during the same year by these colonies. The flowering phenology and nectar and pollen production of the species of Cistus and Halimium found in Hinojos in that period were also recorded. The results show that the apicultural value of the Cistaceae in W Andalusia is limited to the genus Cistus, particularly the species C. iadanifer, C. crispus, C. albidus, C. monspeliensis and C. salvifolius. The importance of each of these species for apiculture varies throughout this territory. In all the Cistaceae species studied, the bulk of the flowering occurred during spring. The period of greatest pollen collection from each species coincided with that of its peak flowering, but pollen grains of these taxa were present in honey produced well outside the flowering periods of these species. Both Cistus and Halimium flowers had very high pollen production but only those of Cistus secreted nectar, with high concentrations of sugar (> 70%). The results suggest that in W Andalusia honey bees visit Cistus flowers mostly to collect pollen.

Paleoenvironmental reconstruction by pollen analysis from loess sequences of the southeast of Buenos Aires (Argentina)

A model of the dynamics of pollen dispersion and deposition in relation to loess deposition is proposed. It is based on pollen analysis of three discontinuous loess sequences of Late Pleistocene-Holocene age, that are located at the archaeological locality of Cerro La China, Buenos Aires Province, Argentina (37° 57′ S.; 58° 37′ W.). Deposition and accumulation of loess and pollen were interpreted in terms of their provenance and transport using the Tauber (1967) and Pye (1987) models for pollen and dust dispersal, respectively. Three pollen zones can be distinguished based on changes in pollen assemblages. The final Late Pleistocene-Early Holocene interval is represented by pollen zone 3. Loess deposits have been accumulated in an environment with a locally high effective moisture. Loess deposition would have occurred synsedimentarily with extra-regional, local and regional pollen taxa. The relationship between pollen dispersal and possible extra-regional pollen sources indicate predominantly W.-SW winds. This zone is truncated by an erosive episode, hence, the successional process of the community could not be reconstructed for the Early Holocene. The Middle Holocene is represented by pollen zone 4. Deposition of loess began in an environment with predominantly herbaceous communities. Pollen concentration increases towards the top of the zone and may represent a buried soil; this would imply a change towards more stable and humid conditions than those at the beginning of the deposition. Extra-regional pollen concentration suggests a comparatively high local and regional pollen productivity rather than a change in wind direction. A slight erosive episode constitutes the upper boundary of zone 4 and is related to new drier conditions. Zone 5 occurs during historical times and is represented by graminous steppe communities and over-representation of local taxa.

A new method of producing 4x hybrid true potato seed

New haploid-wild species hybrids (H-S) with desirable tuber type and 2n gamete production have been identified. They provide the opportunity for the production of inexpensive, 4x hybrid TPS from 2x×2x crosses. A proposed system to utilize plants producing either 2n eggs or 2n pollen is described. One H-S hybrid (female parent) would be selected for male fertility, self-incompatibility, high frequency of 2n eggs and no 2n pollen; an unrelated H-S (male parent) for male fertility and high 2n pollen production. In addition both parents would be selected for profuse flowering, attractiveness to bumblebees and other desirable characteristics. The male and female parents would be planted in alternate hills with bumblebees doing the pollinations. The elimination of emasculation, pollen collection, and hand pollination could reduce 4x hybrid TPS costs by more than 50 percent.

Palynology of the Venezuelan Andes

Abstract The results of palynological analyses from the Merida Andes, Venezuela, from seven stratigraphic sections covering the last 13,000 years are discussed. An interpretation of the climate and vegetation for this time interval shows that the composition of the high montane vegetation and its altitudinal position was not constant during the Late Quaternary, the climate changed at the end of the Pleistocene and there were small oscillations during the Holocene. The representation and abundance of arboreal pollen and spores in the old sediments as compared with modern deposition indicates the presence of: I. families and genera with high pollen or spore production and dispersion (Podocarpus, Alnus, Hedyosmum, and Cyatheaceae); 2. families with low pollen dispersion power, among them the Moraceae and Myrtaceae; 3. one genus among the Compositae (Coespeletia) which is probably anemophilous; 4. one species of montane Gramineae (Pariana stenolemma) which is probably not anemophilous, presenting the first ca...

Palynology ofshorea robusta(dipterocarpaceae) in relation to pollen production and dispersai

Abstract Pollen grains of Shorea robusta Gaertn. (Dipterocarpaceae) were examined with light and scanning electron microscope. The pollen grains are tricolpate with reticulate sculpture with some of the muri discontinuous, giving a canaliculate appearance. The relation between pollen production and dispersal of Shorea robusta reveals that the huge numbers of pollen grains produced is associated with entomophily. The pollen grains have a poor dispersion power as indicated by substantial decline in percentage away from source trees. An extremely low percentage of sal (Shorea robusta) pollen deposited in ground soil within and outside and forest despite the high pollen production which may be attributed to microbial as well as chemical degradation. This information can be utilized for the precise evaluation of pollen diagram in terms of past vegetation and climate from tropical deciduous forests in the Indian sub-continent.

The reproductive biology of the genusBaldellia (Alismataceae)

The reproductive biology of the genusBaldellia was studied under cultivation and in nature.B. ranunculoides subsp.repens is self-incompatible whereasB. ranunculoides subsp.ranunculoides andB. alpestris are self-compatible. Bud-pollination occurs in theB. alpestris. Self-incompatibility correlates with the production of fewer, larger, more showy flowers, higher pollen production (but reduced pollen grain size), fewer carpels and smaller seeds. Resource allocation to sexual reproduction is inversely correlated with the degree of vegetative growth.B. ranunculoides subsp.repens produces more ramets than subsp.ranunculoides, which reproduces mainly by seeds.B. alpestris is intermediate between the two since it is self-compatible, produces fewer, larger seed than subsp.ranunculoides and is also able to propagate by vegetative means.

Pollen Production in Some Anemophilous Angiosperms

Abstract Pollen production in terms of number per anther along with the particulars of anther number per flower, anther length, filament length, pollen grain size and mode of anther dehiscence was determined for 82 angiospermous plant species occurring in Andhra Pradesh, India. Pollen production varied widely from genus to genus, and from species to species within the same genus. The non-Poaceae and non-Cyperaceae members proved to be high pollen producers. The level of pollen production was directly related to anther size and inversely related to pollen grain size. There was no correlation between high pollen production and mode of anther dehiscence in general, but the high pollen producers of Poaceae are porous dehiscing. It is presumed that high pollen producers are crosspollinated, whereas low pollen producers are either self-pollinated or apomictic.

Expression of Andromonoecy and Pollination of Tuberous Lomatiums (Umbelliferae)

Tuberous lomatiums (Lomatium, Umbelliferae) constitute a well-de- fined infrageneric group that is characterized by adaptation to a short, early spring growing season followed by a long summer drought. All tuberous lomatiums are andromonoecious and all exhibit 'a pattern of increasing ratios of hermaphroditic to staminate flowers in successively maturing inflorescences. Floral visitation by a variety of Diptera, Hymenoptera, and Coleoptera effects outcrossing and may also mediate geitonogamous selfing. Xenogamy is promoted by protogyny of hermaphroditic flowers, the arrangement of staminate and perfect flowers, and the sequence of floral maturation. Geitonogamy is favored by the morphology of the inflorescences, overlap of the staminate and pistillate stages of different flowers on the same indi- vidual, and the behavior of pollinators. Andromonoecy and high pollen production favor both xenogamy and geitonogamy. The floral features of tuberous lomatiums ensure relatively high levels of seed production even though abundance and activity of pollinators may be limited by harsh environmental conditions. The characteristic and comparatively uniform inflorescences of the Umbelliferae undoubtedly contributed to early recognition of this nat- ural family. Apparent uniformity may account, in part, for what until recently has been a paucity of investigations into the biological impor- tance of floral features of umbellifers. Studies by Bell (1971), Bell and Lindsey (1978), Brehm (1979), Cruden (1976), Cruden and Hermann- Parker (1977), Lindsey (1982), Lloyd (1973, 1980a, b), Schlessman (1978, 1980), and Webb (1979, 1980) have revealed considerable variation with

EVOLUTIONARY ASPECTS OF WIND POLLINATION IN THE GENUS PLANTAGO (PLANTAGINACEAE)

SUMMARYThe selective forces acting to maintain a copious production of uniformly sized pollen grains in wind‐pollinated plants were investigated among species in the genus Plantago and at the population level in P. lanceolata. The species with cleistogamous (closed) flowers produce far less pollen of more variable average diameters than the species with chasmogamous (open) flowers. Pollen grains of P. lanceolata captured by stigmas of female plants were smaller than a general sample of pollen collected from the anthers of perfect plants, indicating that large pollen grains are not as effective as small grains in wind dispersal. The rapid decrease in pollen density on the stigmas of P. lanceolata with increasing distances from the pollen sources suggests that plants of this self‐incompatible species must produce great amounts of pollen in order to pollinate nearby plants. The cost of this high pollen production associated with wind pollination can be seen in P. lanceolata in the increased production of reproductive tissue and larger seeds in female plants when compared with normal plants.

Some aspects of cross-pollination in wheat (Triticum aestivum L.). 3. Anther length and number of pollen grains per anther

In a search for characters of good pollen donors on the hybrid wheat seed production field, the anther length and number of pollen grains per anther were investigated in five spring wheat varieties. For both characters significant differences were established. Taking 300 anthers per variety, the mean anther lengths varied from 2.99 to 3.84 mm. With the same anthers the mean number of pollen grains per anther ranged from 1746 to 2856. The correlation coefficients of both characters within varieties run from 0.431 to 0.752 and were invariably significant. Linear regression showed that the slopes of the regression lines of the various varieties differed significantly. Combination of a fast increase of the number of pollen grains per anther at increasing anther length and a large anther length should be useful. Between varieties the correlation coefficient of anther length and number of pollen grains per anther amounted to 0.895, significant at a P<0.05. The knowledge that genotypes with large anthers also produce many pollen grains per anther facilitates the selection for a high pollen production per anther. Some relationship appears to exist between number of pollen grains per anther and pollen donor capacity on the field.