Pollen Ovule Research Articles

Chemo and Radio sensitivity to mutagens in Chilli (Capsicum annuumL.).

The effect of gamma rays, EMS mutagens and their combination on chilli genotypes Kashi anmol (KA-2) and VR-338 (Kashi Gaurav) were investigated in M1 generation to assess the radio and/or chemo sensitivity of different doses. Seeds were irradiated with different concentration of Gamma rays, EMS and combinations. With an increase in doses of Gamma rays, EMS and their combinations, substantial increase in pollen sterility and ovule sterility was reported. Gamma rays were more effective for germination percentage as compared to EMS and their combination in both varieties. Seedling height reduction was predominantly observed in EMS as compared to gamma rays and their combination.

Comparative Reproductive Biology and Pollen Limitation ofTamarix chinensisin Wild and Managed Populations in Arid NW China

Tamarix chinensis is ecologically important species in the arid regions of Northwest China. In order to understand its reproductive biology and pollen limitation, flowering dynamics, pollen viability, floral visitors and their behaviors, pollen limitation and breeding system were studied. It was observed that the species show four reproductive characteristics. First, the flower production period and flowering peak were different between wild and managed populations, being longer in the managed. Second, T. chinensis can be pollen-limited, pollen limitation appeared to be proportionally more intense in wild populations than in managed. Third, for the wild, Apis mellifera being the effective pollinators; for the managed, Megachile (Amegachile) kagiana were found to be the most frequent flower visitor. Finally, the pollen ovule rate was 352.3±62.7. We found that out-crossing is dominant in both populations and that selfpollination just played an assistant role to assure production in the breeding system, an informative characteristic that can be used in future reproductive analyses of the both populations.

Assessment of distyly syndrome in Primula palinuri Petagn. a rare species living on maritime vertical cliffs

The distinctive habitat of vertical cliffs provides refuges for many relict plant species. Primula palinuri Petagn. is the only maritime and Mediterranean species of the genus Primula. It only occurs on the cliffs of a narrow area of southern Italy and is classified as being at risk of extinction. Given that only fragmentary information on the biology and ecology of P. palinuri is available, we studied flower morphology, breeding system and other reproductive traits of this species to furnish data for the evaluation of its conservation status. We assessed that plants of P. palinuri develop either long-styled or short-styled flowers and both morphs are equally represented in the studied populations. Reciprocal position of anthers and stigmas is complemented by differences in pollen–ovule ratios, pollen size and exine ornamentation. In both morphs, about 90 % of open-pollinated flowers developed mature capsules and the average number of seeds per capsule was around sixty. Hand pollination experiments showed that reproductive success was high (92.86 and 100 % fruit set) following inter-morph crossings, but no fruit develops after same-morph pollination or selfing. We have ascertained that full distyly syndrome (distinct floral morphs, intra-morph incompatibility and morphs equally represented in the populations) occurs in P. palinuri. However, a further reduction of the severely fragmented range, any rapid change of the environmental conditions due to human impact on coastal areas or stochastic events of plant mortality may alter the proportion of the two morphs, affecting the fragile conservation status of the species.

Breeding system and fruit set in African Marantaceae

Marantaceae are a pantropically distributed family of perennial herbs and lianas in the understory of tropical rainforests. They are characterized by a unique pollen transfer mechanism. To understand its functional significance and evolution, field investigations have been conducted in Gabon.Data from 28 (of 35) species from Central Africa are achieved. The pollen–ovule ratio (34–140:1; exception Sarcophrynium 2.5:1) falls into the range of facultative autogamous species. All investigated species were proven to be self-compatible; however, only two were autogamous. Natural fruit set was generally low (10.9±10%). The highest natural fruit set was found in Marantochloa purpurea (29.7%), Ma. grandiflora (33.5%) and the two autogamous species Halopegia azurea (31%) and Marantochloa leucantha (35%). Considerable higher fruit set could be reached in all species by hand-self-pollination.We conclude that autogamy is generally avoided through herkogamy based on secondary pollen presentation on the back of the style head – a central component of the specific pollen transfer mechanism. However, with respect to the consecutive visit of pollinators to several flowers of the same individual geitonogamy cannot be excluded. The aggregated pollen transfer via the explosive pollination mechanism might be interpreted as an adaptation to low pollinator visitation rate, pollen limitation might explain the low fruit set.

Mating system variation in Veronica (Plantaginaceae): inferences from pollen/ovule ratios and other reproductive traits

The pollen–ovule ratio (P/O) is commonly used to estimate the mode of sexual reproduction in flowering plants. In previous studies, a clear correspondence has been detected between this character and the degree of autogamy. We here investigate variation in this character and its expected correlates in the genus Veronica (Plantaginaceae). Pollen–ovule ratios of 45 species representing eleven percent of all the species in the genus were investigated and compared with results from crossing experiments from previous studies. In addition, multiple populations of 17 of the 45 studied species were sampled and a controlled‐environment experiment was conducted to evaluate the extent of intraspecific variation. Moreover, relationships between P/O and other primary and secondary reproductive characters of the Veronica flower were investigated in relation to a phylogenetic hypothesis in order to determine the phylogenetic constraints on reproductive characters. The differences in P/O among species correspond well to the diversity of mating systems in Veronica and correlate well with other floral characters such as corolla size. These characters together seem to allow a powerful and fast tool to infer mating systems. However, causes for intraspecific variation of P/O, such as different cytotypes, ecotypes or different growth conditions, need to be considered.

Pollination drops as dynamic apoplastic secretions

Pollination drops are apoplastic secretions that are involved in gymnosperm reproduction. Much of the research on pollination drops has been concerned with morphological and phenological descriptions of the drop. Composition analysis has been limited by the phenology and small volume of the drop. Improved proteomics techniques have enabled a more comprehensive analysis of drop composition. It is emerging that the drop is biochemically complex. Many of the components are found in other apoplastic secretions, such as the cell wall proteome, reproductive secretions in angiosperms, floral and extrafloral nectar. In these liquids, proteins confer a variety of functions. In this review, relevant apoplastic secretions are reviewed with an aim to develop a more comprehensive model of dynamic pollination drop function. Comparing pollination drops to other apoplastic secretions reveals similarities that suggest the drop may facilitate pollen–ovule interactions and ovule defense. An example of enzyme activity in the pollination drop is provided. Chitinase activity was detected in the drop of Pseudotsuga menziesii (Douglas-fir) using both a biochemical and an in-gel assay. This shows that one of the putatively identified proteins is active and probably assists in defending the ovule against fungi.

Evidence for autonomous selfing in grassland Protea species (Proteaceae)

It has been assumed that species of the large African genus Protea have strong self-incompatibility systems. However, this assumption was based largely on studies conducted on a clade of bird-pollinated species that occur in the shrubby fynbos vegetation of the Cape region of southern Africa. To test whether self-incompatibility occurs in a grassland/savanna Protea clade, which is largely insect-pollinated, we performed controlled pollination experiments on four species, P. caffra, P. dracomontana, P. simplex and P. welwitschii. Although pollen–ovule ratios of all four species fall within the range for outcrossers, all four species are self-compatible and capable of autonomous seed production. Using fluorescence microscopy, we found that self-pollen tubes had the same probability of reaching ovules as cross-pollen tubes. In the small tree P. caffra, selfed progeny had rates of germination and survivorship that were identical to those of crossed progeny. The grassland Protea spp. studied are likely to have mixed mating systems on account of being both visited by insects and capable of autonomous selfing. If one assumes previous reports of self-incompatibility in Protea to be reliable, there have been at least five losses of self-incompatibility and two gains of autonomous selfing in this genus. However, earlier studies in the genus were often methodologically flawed and a thorough re-analysis of breeding systems in Protea is required. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 433–446.

Pollen Biology of <i>Calligonum mongolicum</i> in the Middle Reaches of Heihe River

The pollen–ovule ratios, pollen fertility rate, pollen viability and longevity, pollen histochemistry of Calligonum mongolicum flowers were determined in the field by the middle reaches of Heihe River. The main results were as follows: Calligonum mongolicum is completely fertile and has starchy pollen. Anthers matured heterotypically. The pollen longevity was about 10h. The pollen viability was higher than 70% at the beginning of anthesis on sunny days. No difference in the pollen production of single anther was found between different flower morphes, but significant difference was in that of single flower. The pollen-ovule ratios of different morph flowers were 1625±125, 1750±177, 1500±102, 1563±120, 1875±72. Pollen–ovule ratios (P/O) reveal that C. mongolicum is facultative autogamous.

Pollen Biology of <i>Robinia pseudoacacia</i> on Zhen Mountain in Yantai

The pollen–ovule ratios, pollen fertility rate, pollen viability and longevity, pollen histochemistry of Robinia pseudoacacia flowers were determined in the field on Zhen Mountain in Yantai, Shandong province in China. The main results were as follows: Robinia pseudoacacia is completely fertile and has starchy pollen. The pollen longevity was about 80h. The pollen viability was higher than 90% at the beginning of anthesis on sunny days. 80h later, most pollen grains lose their viability. Pollen–ovule ratio (P/O) is 192±19. Accoring to Cruden, R. pseudoacacia is facultative autogamous.

Pollen grain size variation in Caryophylloideae: a mixed strategy for pollen deposition along styles with long stigmatic areas?

The literature supports a positive correlation between pollen size and style length and that pollen size may be affected by a trade-off with pollen number. A correlation between pollen size and pollinator type has been hypothesized by some authors but not confirmed. To assess these associations, pollen grain number, pollen grain diameter and style length were measured in 53 species of Caryophylloideae that had been classified beforehand as being diurnal, nocturnal or self-pollinated. Surprisingly, many species showed two, and a few even three, distinct pollen grain size classes per individual anther. Therefore, further analyses were based on the different pollen size classes and respective pollen grain numbers. Firstly, we found no indication of a trade-off between pollen size and number. Secondly, a positive linear correlation between style length and pollen grain diameter was found using conventional analysis methods and phylogenetically independent contrasts. Thirdly, when using conventional analysis methods a strong relationship between style length and pollination mode was found, with nocturnal species having significantly longer styles and larger pollen grains than diurnal and selfing species. These results were not supported, however, when calculating comparisons of phylogenetically independent pairs. We discuss our findings in relation to intra-specific pollen polymorphism and pollen degeneration, both of which have been associated with different pollen grain sizes in Caryophylloideae. Furthermore, we discuss the possibility that pollen polymorphism might be a mixed strategy to optimise the success of pollen grains deposited at different pollen–ovule distances on long styles.

Pollen tetrad segregation and pollen ovule ratios in six species of Acrotriche (Styphelioideae: Ericaceae)

Pollen morphology can be useful in the determination of phylogeny and mating systems of plants. Pollen ovule ratios can give an indication of the mating system of plant species, and there are a number of theories as to reductions in response to pollination strategies. Pollen tetrad segregation occurs when a number of pollen grains within a tetrad abort; this process has evolved a number of times in the family Ericaceae. Pollen ovule ratios along with the total number of tetrads, number of viable grains and proportions of each of the tetrad types were investigated in six species of Acrotriche (Styphelioideae: Ericaceae). Pollen ovule ratios were used in comparison with related species to give indications of mating systems and to examine theories regarding reductions in pollen production. The study species can be arranged into distinct groupings based on the proportions of tetrad types that correlate with floral morphology and may be indicative of phylogentic associations.

Reproductive ecology in the endemic Primula apennina Widmer (Primulaceae)

Disassortative mating in distylous self-incompatible species should result in the equilibrium of morph types in natural populations. Deviation from isoplethy may affect pollen transfer, and in isolated populations it could lead to Allee effect and genetic drift. Pollen limitation has been found to occur in several distylous species, for which mating opportunities are actually reduced to half population. In this study, we investigated the reproductive features and pollination ecology of the narrow endemic Primula apennina. We recorded equilibrium of morph frequencies in the studied population, reflecting the comparable fecundity found in the two morphs. Long-styled flowers produce more pollen grains of smaller size than short-styled ones: we hypothesize that in thrum flowers, pollen is more easily removed by the insect pollinator Macroglossum stellatarum, resulting in equal pollen amounts carried to both short styles and long styles. This lower pollen transfer efficiency from long-styled to short-styled flowers is also reflected in legitimate pollen–ovule ratio values. Despite results show no evidence of imminent threats to population persistence at study site, the strict dependence on one or very few pollinator species, and ecological traits, may increase extinction risks in the long-term period.

ARE RELATIONSHIPS BETWEEN POLLEN-OVULE RATIO AND POLLEN AND SEED SIZE EXPLAINED BY SEX ALLOCATION?

Positive correlations between pollen-ovule ratio and seed size, and negative correlations between pollen-ovule ratio and pollen grain size have been noted frequently in a wide variety of angiosperm taxa. These relationships are commonly explained as a consequence of sex allocation on the basis of a simple model proposed by Charnov. Indeed, the theoretical expectation from the model has been the basis for interest in the empirical pattern. However, the predicted relationship is a necessary consequence of the mathematics of the model, which therefore has little explanatory power, even though its predictions are consistent with empirical results. The evolution of pollen-ovule ratios is likely to depend on selective factors affecting mating system, pollen presentation and dispensing, patterns of pollen receipt, pollen tube competition, female mate choice through embryo abortion, as well as genetic covariances among pollen, ovule, and seed size and other reproductive traits. To the extent the empirical correlations involving pollen-ovule ratios are interesting, they will need explanation in terms of a suite of selective factors. They are not explained simply by sex allocation trade-offs.

Nocturnal and diurnal pollination of Clerodendrum molle (Verbenaceae) in the Galápagos Islands

The primary hypothesis of this study was that in the Galapagos Islands, fruit and seed set via nocturnal pollination would exceed that of diurnal pollination because of the greater insect activity at night typical of hot, arid regions. Clerodendrum molle, a widespread member of the Galapagos flora was submitted to pollination experiments, visitor observations, nectar sampling, pollen transfer studies, pollen–ovule ratio studies, and pollen measurements. Flowers set fruit and seed via open pollination, autonomous autogamy, facilitated autogamy, facilitated cross-pollination, diurnal pollination, and nocturnal pollination. Results indicate no significant difference in fruit set. Cross-pollinated flowers showed a significant increase in seed set over all treatments except facilitated autogamy. Nocturnal and diurnal fruit and seed set did not differ significantly. Nocturnal visitors included ants, spiders, hawk moths, and roaches whereas diurnal visitors included carpenter bees and ants. Galapagos members of C. molle exhibit incomplete protandry and set fruit via autonomous autogamy as a result of natural selection in an environment with few faithful pollinators. Overall low fruit and seed set are likely because of a combination of pollen and resource limitation, the latter exacerbated by nectar robbing. Studies of island angiosperms are crucial for complete understanding of the population dynamics of indigenous plants, which can assist conservation officials in protecting these species.

Reproductive ecology of medicinally important Kashmir Himalayan species of Digitalis L.

AbstractReproductive biology, encompassing phenology, floral biology, pollination and breeding systems, was investigated in three pharmaceutically important and anthropogenically exploited species of Digitalis in the montane habitats of the Kashmir Himalaya. Flowers in all three species (Digitalis purpurea, Digitalis grandiflora and Digitalis lanata) are aggregated in racemes. Corollas are characteristically bell shaped enclosing four, didynamously arranged stamens. The stigma is deeply bifid only in D. purpurea. The three species over‐winter as underground tubers and sprouting during the following spring occurs first in D. lanata, followed by D. purpurea and D. grandiflora. Floral bud opening in an inflorescence in all three species occurs sequentially from the bottom upwards in an acropetal succession and male and female phases are temporally separated with basal flowers entering the male phase first followed by the upper flowers in a regular sequence. Only after shedding the pollen grains completely do the flowers shift to the female phase. Resource allocation in all three species is more towards maleness than femaleness during anthesis. The species are principally insect pollinated and selfing is denied because of protandry and spatial separation of the stigma and anthers. Copious amounts of viable pollen grains produced by these species aid in successful pollination, fertilization and seed production. Studies revealed that none of these species operates autogamy because hand‐pollinated flowers with self‐pollen or bagged flowers (foreign pollen excluded) failed to set seed. High seed output in open‐pollinated flowers and high pollen–ovule ratios also indicate the outbreeding nature of these species. Thus, any reduction in the number of individuals constituting a population would significantly reduce the floral display and consequent rewards to the pollinators, with a subsequent influence on seed production. Hence, data on the reproductive biology of overexploited species, such as Digitalis spp., is of pivotal importance in formulating effective conservation strategies.

How flower biology and breeding system affect the reproductive success of the narrow endemic Polygala vayredae Costa (Polygalaceae)

Polygala vayredae is a narrow endemic species from the oriental pre-Pyrenees. Despite its conservation status and rarity, no information is available on its reproductive biology. As the flower is the structure directly involved in pollinator attraction, its morphological and functional traits have major effects on the reproductive success of the plant. In this work, the flower biology and breeding system of P. vayredae were studied to evaluate how they affect the reproductive outcome in natural populations. Flower morphology, flower rewards, and male and female functioning throughout the lifespan of the flower were assessed. Pollination experiments, involving pollinator exclusion and pollen from different sources, were conducted, and the pollen ovule index was determined. Female fitness and the occurrence of pollen limitation were assessed in three natural populations over 2 years by observing the presence of pollen on the stigma, pollen tube development, and fruit production. Polygala vayredae flowers are elaborate and long-lived with nectar rewards. The floral traits are well adapted to xenogamy and entomophily, which are in accordance with the observed breeding system and auto-incompatibility system. No mechanism of reproductive assurance was observed and P. vayredae strictly depends on pollinators to set fruit. Low fruit production was observed in the studied populations, which was largely the result of scarce, unreliable, and/or inefficient pollinators and poor pollen quality. In addition, available resources may be a limiting factor. The reproductive strategy of P. vayredae prevents inbreeding depression by a self-incompatibility system, which in years of scarce pollinators is overcome by the plant habit.

Evolution of flower morphology, pollen dimorphism, and nectar composition in Arcytophyllum, a distylous genus of Rubiaceae

A phylogenetic study of Arcytophyllum based on ITS was conducted and compared with an earlier study based on cpDNA. The position of the widespread A. thymifolium as sister to all other species was confirmed and several well-supported clades could be retrieved. The Central American A. lavarum is well embedded between exclusively or predominantly South American species. To understand the expression of heterostyly in the genus, we analyzed inter- and intraspecific variation in floral morphology, nectar, pollen–ovule (P/O) ratio and seed set of ten species in 11 populations. Stigma and anther levels differed significantly between the morphs in the species/populations investigated, except for A. filiforme, in which anther levels did not differ significantly between the two morphs. Different expressions of heterostyly in Arcytophyllum seem independent of phylogenetic relationships. Nectar sugar composition was similar between the morphs. Nectar of most species presented a larger proportion of hexoses than of sucrose; only the most derived species, A. macbridei and A. vernicosum, have higher sucrose proportions. There is a significant positive correlation between corolla tube length and the proportion of sucrose. Pollen dimorphism, with regard to both number (long-styled>short-styled) and size (short-styled>long-styled), was observed in all taxa investigated except A. filiforme. According to the P/O ratios, the breeding systems range from facultative autogamy to facultative xenogamy. The lowest P/O ratios were found in A. filiforme, and the highest in A. rivetii. Hymenoptera, Diptera and Coleoptera were observed as flower visitors. Seed production did not differ significantly between the morphs in eight of the 11 species/populations investigated. There is, however, a tendency in all species/populations (except in A. macbridei Peru) for the short-styled morph to have a higher percentage of seeds per ovule, indicating that the short-styled morphs display higher female reproductive success.

Investigation of the breeding systems of four Aizoaceae species in Namaqualand, South Africa

We investigated the breeding systems of four different Aizoaceae species in Namaqualand, South Africa. Results showed that all four species are xenogamous with negligible amounts of seeds produced when flowers are left to spontaneous self-pollination (autogamy) or self-pollinated. Experiments allowing single visits of pollinators resulted in significantly higher seed numbers in relation to bagged unmanipulated flowers for two species. Pollen–ovule ratios were extremely high and supported the notion that the investigated Aizoaceae species are obligate outcrossers depending on insects as pollen vectors.

Relationships between pollen histochemistry, pollen grain number, ovule number and pollinators in Phyllanthaceae

Relationships between pollen histochemistry, pollen grain number, ovule number and pollinators in Phyllanthaceae

Limited ecoclinal variation found in Malva parviflora (small-flowered mallow) across the Mediterranean-climatic agricultural region of Western Australia

Malva parviflora L. populations were collected from 24 locations across the Mediterranean–climatic agricultural region of Western Australia and grown in Perth in a common garden experiment. Seventeen morphometric and taxonomic measurements were taken and genetic variation was investigated by performing principal components analysis (PCA). Taxonomic measurements confirmed that all plants used in the study were M. parviflora. Greater variation occurred within populations than between populations. Separation between populations was only evident between northern and southern populations along principal components 2 (PC2), which was due mainly to flowering time. Flowering time and consequently photoperiod were highly correlated with latitude and regression analysis revealed a close relationship (r2 = 0.6). Additionally, the pollination system of M. parviflora was examined. Plants were able to self-pollinate without the need for external vectors and the pollen–ovule ratio (31 ± 1.3) revealed that M. parviflora is most likely to be an obligate inbreeder with a slight potential for outcrossing. The limited variation of M. parviflora enhances the likelihood of suitable control strategies being effective across a broad area.