Isolation and partial sequence of a Kunitz-type elastase specific inhibitor from marama bean (Tylosema esculentum)

An isolation procedure utilizing ammonium sulfate fractionation and affinity chromatography was used to purify an elastase inhibitor present in large amounts in marama beans (Tylosema esculentum). The protein appeared to be heterogeneous due to carbohydrate differences, demonstrating two bands on SDS gels with molecular weights of 17.8?kDa and 20?kDa. Partial sequence, derived from mass spectrometry, indicated that the protein is a Kunitz-type inhibitor distinct from other known plant serine protease inhibitors. The marama bean inhibitor is specific for elastase, with very low K_i for both pancreatic and neutrophil elastase. The quantity of elastase inhibitor present in marama beans is many times greater than in soybean or any other bean or nut source reported to date. This raises the question of why a bean found in an arid corner of the Kalahari Desert would be so rich in a very potent elastase inhibitor.     

Functional heterostyly in Tylosema esculentum (Caesalpinioideae)

Tylosema esculentum is a long-lived perennial species endemic to arid areas of southern Africa. Its potential as a crop species has long been recognized as a result of the high oil and protein content of its seeds. The reproductive biology and breeding systems of the species were investigated in wild and experimental populations growing in Botswana. Field observations confirmed that the species is heterostylous with the pistil and anthers exhibiting reciprocal heights in the two morphs, although pollen size and sculpturing do not vary. The wet, nonpapillate stigma characteristic of the species is the first to be reported in the Caesalpinioideae. In vivo and in vitro diallel crossing experiments demonstrated that a diallelic self-incompatability system exists in T. esculentum. The major site of pollen tube inhibition in the intramorph crosses was found to be in the style. This is the first report of functional heterostyly in the Fabaceae and of a confirmed self-incompatibility system in the Caesalpinioideae. Three separate lines of evidence, the monitoring of fruit development in open-pollinated plants, fruit set in diallel crossing experiments, and observations made in wild populations, demonstrated that fruit set and, by implication, seed set, are very low in this species. Floral abscission was a major limitation to the production of mature pods but there were also significant losses at other developmental stages of fruit production. The results suggest that low seed set may be an adaptation of the species to an environment in which rainfall is scarce.     

Integration and macroevolutionary patterns in the pollination biology of conifers

Integration influences patterns of trait evolution, but the relationship between these patterns and the degree of trait integration is not well understood. To explore this further, we study a specialized pollination mechanism in conifers whose traits are linked through function but not development. This mechanism depends on interactions among three characters: pollen that is buoyant, ovules that face downward at pollination, and the production of a liquid droplet that buoyant grains float through to enter the ovule. We use a well‐sampled phylogeny of conifers to test correlated evolution among these characters and specific sequences of character change. Using likelihood models of character evolution, we find that pollen morphology and ovule characters evolve in a concerted manner, where the flotation mechanism breaks down irreversibly following changes in orientation or drop production. The breakdown of this functional constraint, which may be facilitated by the lack of developmental integration among the constituent traits, is associated with increased trait variation and more diverse pollination strategies. Although this functional “release” increases diversity in some ways, the irreversible way in which the flotation mechanism is lost may eventually result in its complete disappearance from seed plant reproductive biology.     

Floral biology and pollination strategy of seven Tacca species (Taccaceae)

We investigated the floral characteristics, floral biology and floral visitors of the six Bornean Tacca species: T. bibracteata (only floral characteristics), T. borneensis, T. havilandii, T. leontopetaloides, T. palmata and T. reducta, and T. cristata from Peninsular Malaysia. All species are protogynous with pollen strings extruded post flower opening. Blooming of all species started from dawn except for T. leontopetaloides which flowered from dusk. While T. borneensis, T. cristata, T. havilandii, T. leontopetaloides and T. reducta are facultatively autogamic as the pollen/ovule ratios (P/O ratios) were low, T. bibracteata is facultatively xenogamic as its P/O ratio was higher. Four species (T. borneensis, T. cristata, T. havilandii and T. reducta) were tested for autonomous self-pollination but all failed to set fruit. Manual self- and cross-pollination treatments of T. borneensis, T. cristata and T. havilandii showed reduced fruit set and seed set. In contrast, T. reducta was highly self-compatible. The showy bracts and bracteoles of T. borneensis are needed to guarantee pollination success but is not so in the other species investigated. Tacca are pollinated by two pollination guilds of female midges: two species of Forcipomyia (Lasiohelea) and Culicoides hinnoi. The floral biology and mating system of Tacca species indicate that most fruits and seeds were produced in samples resulting from natural pollination.     

Male interference with pollination efficiency in a hermaphroditic orchid

Hermaphroditism can lead to both intra‐ and intersexual conflict between male and female gender functions. However, the effect that such gender conflicts have on pollination efficiency has seldom been investigated. By artificially reducing the number of available male gametes on an individual, we quantified whether male interference with pollination efficiency occurs in the self‐compatible, moth‐pollinated orchid Satyrium longicauda. We partially emasculated S. longicauda inflorescences and compared pollination success and fecundity in these plants to intact controls. Pollen in both groups of plants was colour‐labelled so that its dispersal by pollinators could be tracked directly in the field. Intact flowers on partially emasculated inflorescences exported more pollen and received more cross‐pollen and less self‐pollen than those on intact inflorescences. Proportion of fruit set per plant was similar between the two treatments; however, fruits on partially emasculated plants had proportionally more viable seeds than those on intact controls. These results provide empirical evidence that male interference with pollination efficiency can occur in a hermaphroditic plant and that such interference can compromise fecundity. The most likely mechanism for such male interference is competition for placement on the proboscis of hawkmoth pollinators. Consequently, male competition for siring success may influence the evolution of sexual systems in hermaphroditic pollinator‐dependent plants.     

Effects of pollination intensity on the vigor of the sporophytic and gametophytic generation of Cucurbita texana

 We examined the effects of pollen competition (pollen load size) on sporophytic vigor and gametophytic performance in Cucurbita texana, a wild gourd, while controlling for alternative interpretations of the data. Under field conditions we compared the vigor of progeny produced from large and small pollen loads and examined the in vitro performance of the pollen produced by the progeny. We found that the progeny from large pollen loads germinated faster and had a greater reproductive output (male flowers and fruits) than progeny produced from small pollen loads. In addition, we found that the pollen produced on plants derived from large pollen loads grew faster in vitro than the pollen produced on plants derived from small pollen loads. These findings indicate that pollen competition affects the performance of the resulting sporophytic generation and the microgametophytes they produce. Received: 26 January 1997 / Revision accepted: 25 June 1997     

Anther opening, pollen biology and stigma receptivity in the long blooming species, Parietaria judaica L. (Urticaceae)

Background and aimsThis paper is about pollen ecophysiology, anther opening, pollen dispersal and the timing of the male and female phases in Parietaria judaica (Urticaceae).MethodsEcophysiological (effects of different relative humidities (RHs) and osmotic relationships) and cytological methods (stigmatic receptivity, pollen viability, histology and histochemistry) were used to determine pollen and pollination features during the long blooming period of this species.Key resultsPollen is dispersed by rapid uncurling of the filament and anther opening. The filament and anther lack cells with lignified wall thickenings, which are usually responsible for anther opening and ballistic pollen dispersal. Instead, dispersal is the result of the sudden movement of the filament. Pollen is of the partially hydrated type, i.e. with a water content greater than 30% at shedding, and readily loses water, and hence viability, at low RH. Pollen carbohydrate reserves differ with season. Starchless grains germinate quickly and are less subject to water loss. Flowers are protogynous, pollen release occurring only after complete cessation of the female phase within an inflorescence.ConclusionParietaria has partially hydrated pollen which differs from typical pollen of this type because of its reduced size and the absence of callose. Because of its low water content at the time of shedding it survives better at higher RH. Dispersal and pollination are adapted to pollen features.     

Heterostyly promotes compatible pollination in buckwheats: Comparisons of intraflower,intraplant, and interplant pollen flow in distylous and homostylous Fagopyrum

Premise of the Study

Heterostyly, the reciprocal positioning of stigmas and anthers in different floral morphs, has long been thought to promote intermorph pollination. However, extensive intramorph pollination occurs commonly in heterostylous species, leading to recurrent questions about the functional and evolutionary significance of heterostyly.

Methods

To identify the sources of stigmatic pollen (autogamous [intraflower], geitonogamous [intraplant], vs. interplant), we emasculated either one flower or entire plants in experimental populations of the two closely related buckwheat species, distylous Fagopyrum esculentum and homostylous F. tataricum. Differences in pollen size allowed unambiguous identification of pollen on stigmas.

Results

Only 2.4% of F. tataricum pollen and 1.5% of F. esculentum pollen arrived successfully on compatible stigmas of other plants. In the former (homostylous) species, 71.3% of the pollen load on stigmas was autogamous, 10.8% was geitonogamous, and 17.9% was interplant. In the latter (distylous) species, 37.45% of the pollen on stigmas was autogamous, 13.8% was geitonogamous, 17.0% was intramorph, and 31.75% was intermorph. The amount of incompatible pollen arriving on stigmas was greatly decreased by both one‐flower and whole‐plant emasculations, and thus, the proportion of compatible pollen deposited increased with one‐flower emasculation and increased even more with whole‐plant emasculation.

Conclusions

Our quantification of pollen‐donor sources in these two species indicated that heterostyly in Fagopyrum esculentum provided a nearly 2‐fold fitness advantage (in terms of compatible pollination) over expected (random) pollen transfers between morphs. Because of reduced herkogamy, the homostylous F. tataricum was highly autogamous.     

Associations among components of the male germ unit followingin vivo pollination in barley

Summary The male gametophyte of barley has been studied during post-pollination stages from the time of pollen activation through pollen tube growth to the level of the ovule. Techniques included the use of serial thick sectioning, serial ultrathin sectioning of re-embedded thick sections, and computer generation as well as manual production of three-dimensional reconstructions. It was found that after pollination, but before the sperms exit the pollen grain, an intimate association is formed between the vegetative nucleus and the two sperms, and between the sperms themselves. The latter association is maintained through the duration of pollen tube growth observed in this study. These results indicate that the male germ unit of barley, a grass, is ultimately similar to that of other angiosperms studied thus far at the electron microscope level and that the concept of the male germ unit may have even greater significance and application within flowering plants than previously thought.     

'Anti-bee' and 'pro-bird' changes during the evolution of hummingbird pollination in Penstemon flowers

Floral phenotypes may be as much the result of selection for avoidance of some animal visitors as selection for improving the interaction with better pollinators. When specializing on hummingbird-pollination, Penstemon flowers may have evolved to improve the morphological fit between bird and flower, or to exclude less-efficient bees, or both. We hypothesized how such selection might work on four floral characters that affect the mechanics of pollen transfer: anther/stigma exsertion, presence of a lower corolla lip, width of the corolla tube, and angle of flower inclination. We surgically modified bee-pollinated P. strictus flowers changing one trait at a time to make them resemble hummingbird-pollinated P. barbatus flowers, and measured pollen transfer by bumblebees and hummingbirds. Results suggest that, apart from 'pro-bird' adaptations, specific 'anti-bee' adaptations have been important in shaping hummingbird-flowers. Moreover, some trait changes may have been selected for only if changing in concert with other traits.     

Mating system and pollination biology of a high-mountain perennial plant,Rhodiola dumulosa (Crassulaceae)

Aims Rhodiola dumulosa is a perennial herb growing in a naturally fragmented habitat of high-mountain rocks. This research aims to (i) investigate the mating system characteristics and pollination biology of R. dumulosa, (ii) study the effects of ecological factors on the mating system and pollination biology of R. dumulosa and (iii) assess the relationship between its pollination and mating system.Methods Mating system parameters were analysed using allozyme markers. Growth of pollen tubes from artificial self- and cross-pollination was also examined. Field investigations were conducted on insect flower visitation during the blooming period of R. dumulosa. Relationships among mating system, insect flower visitation frequency and environmental factors were assessed.Important findings The results showed that (i) R. dumulosa has a mixed-mating system: it is self-compatible and primarily outbreeding, with the multilocus outcrossing rate (t m) ranging from 0.589 ± 0.078 (± standard deviation) to 0.846 ± 0.077; inbreeding coefficients of maternal parents (F) were zero, indicating that inbreeding depression was intense. (ii) Light intensity and temperature impacted the visitation of the principal pollinators, the syrphid Eristalis tenax and the bumblebee Bombus pyrosoma. (iii) Population size plays an important role in the mating system and pollination. Populations received more frequent visits by the principal pollinators usually had higher outcrossing rates. Pollination to some extent affects the mating system of R. dumulosa and it is important to maintain large populations to prevent further inbreeding and to maintain pollinators to facilitate outcrossing.     

The use of the pheno-climatic model for forecasting the pollination of some arboreal taxa

Air temperature is one of the most frequent parameters for the application of pheno-climatic models which can give information for the forecasting of the beginning of pollination of various species. For the present study 12 years of aerobiological monitoring data concerning the pollination of hazel, alder, elm, poplar, and willow have been employed to forecast the beginning of their pollination assuming that the beginning of pollination of one species corresponds to a specific moment of phenological development for another species with later pollination. The difference expressed in days between the pollination of two winter taxa with successive flowering is very variable. If this interval is expressed in terms of heat (summation of mean daily temperature above a certain threshold) the differences are smaller. The delay between the pollination of alder and elm varies between 3 and 21 days depending on the climatic trend, but during this period elm on average accumulates 26 degree-days (base temperature 4°C) with a lesser variability. In this way we can begin to calculate the heat requirement for elm from the beginning of alder flowering. This application can be used for other couples obtaining statistical values which are more significant than those obtained with the phenological model, with the exception of willow. The results indicate that for the majority of the species with winter flowering there is a linear relation between the flowering dates and air temperature.     

Forecast of the Poaceae pollination in Zurich and Basle (Switzerland)

A simple formula, intended to serve as an aid for the prevention of allergies, is proposed for forecasting the starting date of the grass pollination season in Switzerland. Parameters are daily mean air temperature and rainfall. The forecast is accurate in two thirds of the cases, and too early in one third, but still useful in practice.     

The use of sieving during standard pollen pre-treatment of samples of fossil deposits to enhance the concentration of large pollen grains

Small pollen grains and fine particles of the organic matrix in samples of a coarse detritus mud and a blanket peal deposit were removed by sieving through 30μ polyester mesh after digestion with KOH and acetolysis during standard pollen pre-treatment. The technique enhanced the number of large pollen grains m the sample. There was also an increase in the range of taxa which produce huge grains. The method provided a means of estimating the ratio of any scarce large pollen grain to the total grain sum in samples prepared by standard methods of pre-treatment.     

Correlation between pollen morphology and pollination mechanisms in the Hydrocharitaceae

The pollen morphology of 11 genera and 11 species of the Hydrocharitaceae and one species of the Najadaceae was studied using scanning and transmission electron microscopies, and the exine structures and sculptures are discussed in relation to pollination mechanisms and the molecular phylogeny. The pollen grains of the Hydrocharitaceae are spherical, inaperturate, and form monads or tetrads, while those of the Najadaceae are elliptical, inaperturate, and form monads. The entomophilous genera Egeria, Blyxa, Ottelia, Stratiotes, and Hydrocharis share pollen grains that have projections like spines or bacula. The anemophilous genus Limnobium has reticulate pollen grains. The hypohydrophilous genera Thalassia and Najas are characterized by pollen grains with reduced exine structures. The pollen-epihydrophilous genera Elodea and Hydrilla have tightly arranged small spinous pollen grains, and the male flower-epihydrophilous genera Enhalus and Vallisneria have reduced reticulate or gemmate exines. Character state reconstruction of the exine structures and sculptures using a molecular phylogenetic tree suggests that variation in the exine is generally correlated with the pollination mechanism; the selective pressures acting on the pollination mechanisms have reduced the exine structure in hypohydrophilous plants and resulted in various exine sculptures that are adapted to the different pollination mechanisms in entomophilous, anemophilous, and pollen-epihydrophilous plants.     

Selection for pollination success and the mechanical fit of Imfiatiens flowers around bumblebee bodies

Selection on flowers has often been viewed as being particularly strict, constant, and responsible for species differences. Impatiens pallida and I . capensis flowers fit snugly around bees, leading one to expect a close relationship between floral morphology and pollination success. My studies on the amount of pollen removed from androecia and deposited on stigmas in single visits by bumblebees did not confirm this supposition. Trimming off parts of the floral vestibule with scissors and gluing in pleats had very little effect on die amount of pollen that bees moved. In reciprocal transfer experiments, flowers from different populations sometimes differed in the amount of pollen moved, but when the two species were compared in sympatry, pollen removal and deposition differed hardly at all. A comparison of the relationship between pollen movement and floral morphology among 15 populations showed that, although there was great heterogeneity in die amount of pollen moved, the observed differences were independent of floral morphology. None of this supports a belief in strong selection that fine-tunes the mechanical fit between bee and flower; selection for visitation success based on pollinator behaviour may have a much stronger influence on floral characters.     

The number of cells in the pollen of Melastomataceae (Myrtales)

The mature pollen of Melastomataceae is not three-celled, as reported earlier, but two-celled. Two-celled mature pollen is characteristic of all Myrtales, excluding Thymelaeaceae.     

芍药的传粉生物学研究

对内蒙古赤峰市高格斯台罕乌拉自然保护区2个自然居群和内蒙古农校芍药园内2个栽培品种的芍药进行了连续2年的观察和研究表明,不同居群、不同品种的芍药花期相同,均为23~27d。芍药不存在无融合生殖,有微弱的自交性,不存在闭花授粉的现象。是以昆虫为媒介以异交为主要传粉方式的物种。不同花期的结实率之间没有显著差异(F=1.501)。芍药的结实率较低,野生居群平均只有23.27%的胚珠发育成种子。两个野生居群的传粉强度和传粉效率小于栽培品种单瓣花,结实率也低于栽培品种单瓣花。三个实验样地不同居群间的人工授粉结实率基本一致,且均高于其他组合。     

Any which way will do – the pollination biology of a northern Australian rainforest canopy tree (Syzygium sayeri; Myrtaceae)

The pollination biology of Syzygium sayeri was documented using the special capabilities of the Australian Canopy Crane. Syzygium sayeri is a xenogamous species with poor self-compatibility, moderate levels of natural out-crossing, and the producer of copious amounts nectar throughout the day and night. Of a diverse fauna associated with, and visiting the flowers of S. sayeri , larger vertebrates (blossom bats and honeyeaters) account for approximately half its natural pollination rate, while the balance of pollination is attributable to a host of invertebrate visitors (wasps, flies, thrips, butterflies). Day and night pollinators contributed approximately equally to the successful pollination of S. sayeri ; although the number of individuals visiting flowers was greater during the day, further experimentation might reveal night visitors to be more effective pollinators. The co-occurrence of vertebrates and invertebrates, as well as day and night visitors, suggests that S. sayeri has a generalist pollination system, whereby the absence of a discrete set of faunae could be compensated for by the presence of other pollinators. What is not clear is the contribution of different pollinators to the population success (i.e. gene flow) of this species. Further study is needed to determine the contribution of each pollinator group to the flow of genetic material in populations of S. sayeri . © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 69–84.     

Beginning of pollen flight information in the former German Democratic Republic

Volumetric air sampling via the Burkard pollen and spore trap is described. The influence of meteorological factors on the occurrence of airborne pollen was investigated; the concentration of pollen grains is increased in strata of reduced vertical air exchange. A pollen flight information service has been developed since 1989 for Erfurt and other areas in the former German Democratic Republic.