Self-pollinated Flowers Research Articles

Effect of pollination methods on fruit set and physical characteristics of litchi fruits

An experiment was conducted in tarai region of Uttarakhand, to study the effect of different parent combinations in four commercial litchi cultivars (‘Rose Scented’, ‘Calcuttia’, ‘Early Seedless’ and ‘Late Seedless’) as a result of self, cross and open-pollination methods during two successive years (2013 & 2014). The two-year pooled data indicated the initial fruit set (%) was significantly lower in all cross pollination methods, i.e., 38.55% (Early Seedless × Calcuttia) compared to self-pollination method, i.e., 72.78% in Rose Scented × Rose Scented. However, final fruit retention was significantly higher in all cross-pollinated flowers, i.e., 24.68% (Rose Scented × Early Seedless) compared to self-pollinated flowers, i.e., 8.65% (Early Seedless × Early Seedless). Fruit weight (24.33 g) in Late Seedless × Early Seedless, Fruit length (3.66 cm) in Late Seedless × Early Seedless, peel weight (5.19 g) in Early Seedless × Late Seedless, aril weight (18.66 g) in Late Seedless × Early Seedless and seed weight (3.81 g) in Calcuttia × Rose Scented were significantly increased in cross-pollination methods. However, the maximum fruit width (3.00 cm) was recorded in open-pollinated Late Seedless. Overall, increased fruit retention and fruit physical characteristics under the cross pollination suggests that the inclusion of crosspollinators in litchi orchards may have beneficial effects on production.

Biosystematic studies on the mountain plant Gentiana lutea L. reveal variability in reproductive traits among subspecies

Background: Taxonomic analysis provides a basic understanding for taxon identification and contributes to preliminary information for several branches of applied biology, while studies on reproductive strategies and plant fitness are essential to interpret population status and dynamics.Aims: We tested the reliability of diagnostic characters for identification and to characterise sexual resource allocation, the breeding system and seed predation among subspecies of Gentiana lutea.Methods: We analysed morphological characters in 70 herbarium specimens. In five natural populations we counted pollen and ovule numbers, assessed reproductive output after pollination treatments and evaluated pre-dispersal predation.Results: Taxonomic traits previously indicated as diagnostic were not sufficient to discriminate among subspecies. The pollen number and pollen:ovule (P:O) ratio varied strongly among subspecies; self-pollinated flowers produced a significantly lower number of seeds than open-pollinated flowers. Retention of empty fruits and high levels of pre-dispersal seed predation were observed in every case.Conclusions: The variation of P:O ratios among subspecies suggests different efficiency in pollen transfer. The species is self-compatible, nevertheless all subspecies require pollen vectors to enhance cross pollination and viable seed production. Fruit retention may have evolved as a strategy to reduce predation, ensuring higher plant fitness.

Mating system modulates degree of seed dormancy inHypericum elodesL. (Hypericaceae)

AbstractKnowledge of processes responsible for seed dormancy can improve our understanding of the evolutionary dynamics of reproductive systems. We examined the influence of the breeding system on primary seed dormancy inHypericum elodes, an Atlantic–European softwater pools specialist plant that exhibits a mixed mating strategy (the ability to both self- and cross-pollinate) to set seeds. Seeds were obtained through hand pollination treatments performed in a natural population during three consecutive years. Primary dormancy of seeds recovered from each pollination treatment was measured by analysing the seed germination response at dispersal and after various periods of cold stratification. While all collected seeds exhibited physiological dormancy, the degree of primary dormancy was associated with the pollination treatments. Weak and rapid loss of primary dormancy characterized seeds recovered from self-pollinated flowers, while stronger dormancy was found in seeds obtained from cross-pollination. The association between pollination treatments and primary dormancy indicated that the mating system should be considered as a source of variation for dormancy degree, proportional to self- and cross-pollinations (selfing rate) within populations of this species. These results suggest that by shedding seeds with various degrees of dormancy, plants may distribute their offspring across time by means of polymorphism in germination response. We conclude that seed germination alone is not an appropriate fitness measure for inbreeding depression estimates, unless dormancy is removed.

Effects of Self, Open, and Supplementary Pollination on Growth Pattern and Characteristics of Pomegranate Fruit

In the present study the type of pomegranate pollination and its effects on fruit growth pattern and fruit characteristics were investigated throughout the growing season. Adequate flowers of three cultivars were selected and tagged after self and supplementary pollination and intact flowers were allowed for open pollination. Quantitative traits (weight, diameter, and length) of fruit and arils were improved by open and supplementary pollination. Within the qualitative parameters, seed firmness was decreased in open and supplementary pollination especially in ‘Gorch-e-dadashi’ and ‘Zagh-e-yazdi’. Also, seed length was increased by open pollination in ‘Zagh-e-yazdi’, although it was decreased in ‘Postghermez-e-aliaghaei’ and not influenced in ‘Gorch-e-dadashi’. The rate of self-fertility varies between three studied cultivars of pomegranate and Poost ghermez-e-aliaghaei had more self-fertility than Gorch-e-dadashi and Zagh-e-yazdi. Also the results showed a decrease in arils number, fruit, and seed weight of self-pollinated flowers compared to open and supplementary treatment, which could be considered as an existence of incomplete self-compatibility. In conclusion, this research provides further evidence that pollination in terms of open and supplementary is necessary for increasing the quantity and quality potential of fruits in commercial pomegranate production.

Ovarian self-incompatibility inNarcissus papyraceus(Amaryllidaceae) is the result of a pre-zygotic response

Ovarian self-incompatibility, including pre- and post-zygotic reactions, is a complex mechanism for which we still lack many details relating to its function and significance. The joint presence of ovarian self-incompatibility with style polymorphism is a rare combination that is found in the genus Narcissus. Usually, style polymorphic species have heteromorphic (diallelic and linked to style length locus) incompatibility, which prevents fertilization between individuals of the same morph, thereby helping to maintain equal proportions of floral morphs in populations. However, when present, self-incompatibility in Narcissus is not linked to style polymorphism and cross-fertilization within each morph is possible. Hence, self-incompatibility in Narcissus is of particular interest when attempting to unravel the nature of the rejection reaction and aiming to assess possible cryptic differences in the fertilization process in intra- and inter-morph crosses, which might ultimately explain the wide variation of morph-ratio in the field. We examined the breeding system of Narcissus papyraceus, a style-dimorphic species that has biased morph ratios in most of its populations. We studied pollen-tube growth in the pistil and ovule fate after experimentally controlled hand pollinations. The growth of pollen tubes in self- and intra- and inter-morph crosses was similar up to the point of micropyle penetration in both morphs but, subsequently, a pre-zygotic failure appeared to affect male and female gametophytes in selfed pistils. A high proportion of ovules from self-pollinated flowers showed signs of collapse and self-pollen tubes were blocked or behaved abnormally before entering the embryo sac. Self-incompatibility was stronger in the long-styled morph than in the short-styled morph. We did not find any conclusive sign of differential functioning between intra- and inter-morph cross-pollinations in any morph. These results enable us to rule out the possible effects of pollen–pistil interactions in N. papyraceus as a cause of morph-ratio biases and confirm the exceptional nature of the self-incompatibility mechanism in this polymorphic species.

English

Gossypium hirsutum flowers are easily emasculated by splitting the staminal column with the fingernail and removing the corolla and androecium. However, any damage to the ovary is considered detrimental to successful boll formation and damaged flowers are typically discarded.  This study evaluated boll retention after different emasculation treatments. Removal of the membrane surrounding the ovary reduces boll retention compared to self-pollinated flowers, and showed a similar response across 18 genotypes.  Damage to the ovary wall reduced boll retention compared to emasculate flowers without ovary damage. Damaged flowers could be cross-pollinated to produce additional bolls as compared to discarding the flowers.   Key words:  Breeding, emasculation, Gossypium hirsutum, hybridization

Does Oeceoclades maculata (Orchidaceae) reabsorb nectar?

Nectar is the most common resource offered by orchid flowers. In some cases, flowers reabsorb nectar as part of a resource-recovery strategy. Nectar is present only in the morning in the widespread orchid Oececoclades maculata (Lindl.) Lindl. To determine whether this is due to reabsorption or evaporation of water, the volume of nectar and its concentration in previously bagged flowers were determined throughout the day at two hourly intervals. In addition, the entrance to the nectary of flowers of cultivated plants was obstructed with petroleum jelly in the morning, to prevent the evaporation of water and, in the afternoon, the presence of nectar was recorded. Furthermore, manually self-pollinated flowers, also with the entrance to the nectary obstructed, had their nectary checked 24 hours after pollination to determine whether post-pollination reabsorption occurred. In addition, the period when the pollinators of O. maculata foraged for nectar was determined in order to establish whether it was associated with the period when nectar was available. The volume and concentration of nectar in O. maculata flowers vary from 0.82 μl (25.10%) between 10–12 h and 0.36 μl (33.73%) between 16–18 h and this difference is caused by evaporation of water. Post-pollination reabsorption does not occur in this species. Pollinators forage most actively between 10–12 h. Thus, O. maculata does not reabsorb nectar, but evaporative water loss is a significant factor determining the variation in the volume and concentration of this reward and this is positively correlated with butterfly visitation.

Oil collecting bees and Byrsonima cydoniifolia A. Juss. (Malpighiaceae) interactions: the prevalence of long-distance cross pollination driving reproductive success

Oil-collecting bees are the natural pollinators of oil-flower plants, but little is known about the pollination process and the effectiveness of their pollination service to the reproductive success of their host plants. In species of Byrsonima the reproductive system have been described as auto-compatible or self-incompatible. We studied the reproductive system of Byrsonima cydoniifolia, the fructification by means of short, medium and long-distance cross pollinations, the morphology and floral biology and the pollination interactions with species of oil-collecting bees. By means of controlled pollinations we found self-incompatibility caused by abortion of most self-pollinated flowers and demonstrated that the prevailing cross pollination ensuring the reproductive success of B. cydoniifolia is the long-distance cross pollination and Centridini bees; Epicharis nigrita, particularly, are the pollinators promoting the gene flow between genetically distinct populations.

Self-incompatibility, parthenocarpy and reduction of seed presence in ‘Afourer’ mandarin

Seedlessness is one of the main requirements for the Citrus fresh market. ‘Afourer’ mandarin has been registered as self-incompatible, producing seedless fruit in the absence of cross-pollination. Under field conditions, a high number of seeded fruits is produced, which reduces its quality and commercial value. The purpose of this work was to characterize self-incompatibility type of ‘Afourer’ mandarin, to determine its parthenocarpic capacity, and to reduce the presence of seeds under field conditions. Four experiments were performed, including net-covered trees during flowering period (experiments 1 and 2), single flower emasculation and self-pollination (experiment 3), in vivo pollen germination, pollen tube development and ovule viability (experiment 1), and field application of copper sulfate (CuSO4) and gibberellic acid (GA3) during flowering period (experiment 4); open pollination was the control in all situations. Under open pollination, relatively low seedless fruit percentage was found (7% and 34%), whereas with anti-bee nets this percentage reached 98–99% of the fruits. Relatively high fruit set percentage and fruit number per tree was found in net-covered trees and in bagged or emasculated flowers, indicating that ‘Afourer’ mandarin presents facultative parthenocarpy. Emasculated or self-pollinated flowers resulted in similar seedless fruit number, indicating an autonomous parthenocarpy. In flowers from open or net-covered trees, similar pollen tube growth was registered until 6 days after anthesis, but, thereafter, growth was interrupted in self-pollination condition, reaching only 40% of the style length, which suggests a gametophytic self-incompatibility system. GA3 applied during flowering period reduced the percentage of seeded fruits and seed number per fruit; the most efficient treatment was three applications of GA3 (50mgl−1) combined with CuSO4 (25mgl−1), that increased seedless fruit from 19% to 31% and reduced from 3.7 to 2.3 the number of seeds per fruit.

Contrasting breeding systems in six species of Tillandsia L. (Bromeliaceae) from woody areas of Santa Fe Province: Argentina

The reproductive biology of six native Tillandsia species that co-occurred in woody areas of Santa Fe Province (Argentina) was studied for floral biology, breeding systems and reproductive success. Flower longevity, floral phases, hand self- and cross-pollinations or natural pollinations and fluorescence microscopy observations of post-pollination events were analysed. Also pollen/ovule (P/O) ratio and pre-emergent reproductive success (PERS) were compared between species. In T. aëranthos, T. ixioides and T. meridionalis, self-pollinated flowers mostly failed to form fruits, and fluorescence microscopy studies showed that in selfed pistils pollen tube growth was arrested in the style. It is likely that these species have homomorphic, gametophytic self-incompatibility. In contrast, T. capillaris, T. tricholepis and T. recurvata regularly formed fruits following autonomous self-pollination. Floral traits, the P/O ratios and PERS indices correlate with the breeding systems found in these two groups of species: the three selfing species have inconspicuous closed flowers, and they have low P/O ratios and high PERS values. In contrast, the three self-incompatible (SI) species have conspicuous flowers with relatively high P/O and low PERS values. We described here three new cases of SI in Tillandsia species subgenera Anoplophytum and confirm the autogamous and cleistogamous status in three species of Tillandsia subgenera Diaphoranthema.

The effect of temperature and genotype on pollen performance in olive (Olea europaea L.)

The reproductive phase has proven to be one of the most temperature sensitive stages in plants. Relatively high or low temperatures, especially during the progamic phase, are often correlated with low fertilization percentages and low fruit setting in different years and orchards. Here, the olive variety ‘Oblica’ was employed in a two year field experiment to assess the effect of temperature on the duration of the flowering period as well as on pollen germination, pollen tube growth, and fertilization percentage. An increase in temperature in the field was caused by covering trees with polyethylene cages. Cultivars ‘Leccino’ and ‘Levantinka’ were used as pollen donor genotypes in the cross-pollination treatment, and pollen from ‘Oblica’ trees was applied in the self-pollination treatment. Pollen germination in vitro was enhanced when pollen grains were exposed to higher temperatures two days before the start of flowering (29% for covered trees vs. 17% for uncovered trees in 2009; and 12.3% vs. 10% in 2010). Higher temperatures advanced the appearance of full bloom and shortened the duration of flowering period by one day for ‘Oblica’ trees inside the cages. No significant difference in pollen germination on the stigma was observed between the trees exposed to different temperatures. Pollen donor genotype affected pollen germination in vivo. Temperature had significant influence on pollen tube growth in the style and on fertilization percentage, but the reaction was genotype dependent. Higher temperatures reduced pollen tube growth in the style (decrease for 17% in 2009 and for 9% in 2010) and fertilization percentage (decrease for 9% in 2009 and for 8% in 2010) by increasing the time required for pollen tubes to reach the base of the style or the ovule. Due to faster pollen tube growth, the percentages of pollen tube growth and fertilization were significantly higher in cross-pollinated flowers (94.9% in 2009 and 70.9% in 2010 for pollen tube growth; 58.9% in 2009 and 51.4% in 2010 for fertilization) than in self-pollinated flowers (35.4% in 2009 and 59.6% in 2010 for pollen tube growth; 19.3% in 2009 and 39.1% in 2010 for fertilization). The results of our study support the model that the self-incompatibility level in olive is regulated by temperature because differences in self-fertilization percentage were observed between ‘Oblica’ trees outside and inside the polyethylene cages.

S-HAPLOTYPES AND SELF-COMPATIBILITY OF THE JAPANESE PLUM CULTIVAR 'KARARI'

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Genomics and Genetic Transformation of Horticultural Crops S-HAPLOTYPES AND SELF-COMPATIBILITY OF THE JAPANESE PLUM CULTIVAR 'KARARI'

Environmental control of reproductive phenology and the effect of pollen supplementation on resource allocation in the cleistogamous weed, Ruellia nudiflora (Acanthaceae)

Mixed reproductive strategies may have evolved as a response of plants to cope with environmental variation. One example of a mixed reproductive strategy is dimorphic cleistogamy, where a single plant produces closed, obligately self-pollinated (CL) flowers and open, potentially outcrossed (CH) flowers. Frequently, optimal environmental conditions favour production of more costly CH structures whilst economical and reliable CL structures are produced under less favourable conditions. In this study we explore (1) the effect of light and water on the reproductive phenology and (2) the effect of pollen supplementation on resource allocation to seeds in the cleistogamous weed Ruellia nudiflora. Split-plot field experiments were carried out to assess the effect of shade (two levels: ambient light vs. a reduction of 50 %) and watering (two levels: non-watered vs. watered) on the onset, end and duration of the production of three reproductive structures: CH flowers, CH fruit and CL fruit. We also looked at the effect of these environmental factors on biomass allocation to seeds (seed weight) from obligately self-pollinated flowers (CL), open-pollinated CH flowers and pollen-supplemented CH flowers. CH structures were produced for a briefer period and ended earlier under shaded conditions. These conditions also resulted in an earlier production of CL fruit. Shaded conditions also produced greater biomass allocation to CH seeds receiving extra pollen. Sub-optimal (shaded) conditions resulted in a briefer production period of CH structures whilst these same conditions resulted in an earlier production of CL structures. However, under sub-optimal conditions, plants also allocated more resources to seeds sired from CH flowers receiving large pollen loads. Earlier production of reproductive structures and relatively larger seed might improve subsequent success of CL and pollen-supplemented CH seeds, respectively.

BIOLOGÍA REPRODUCTIVA DE GOMESA BIFOLIA (ORCHIDACEAE, CYMBIDIEAE, ONCIDIINAE)

Gomesa bifolia (Orchidaceae, Cymbidieae, Oncidiinae) is an epiphytic orchid that presents showy yellow flowers with brown markings on sepals and petals, fragranceless and with oil as reward. The floral biology of this species was studied in cultivated individuals to describe phenology, flower longevity, reproductive system (using manipulative treatment of cross-pollination vs. self-pollination) and floral pollinators. Moreover, direct observations were made on plants exposed outdoors to identify pollinators, describing their foraging behavior and the duration of visits. The results showed that G. bifolia is a mainly self-incompatible, non-autogamous and pollinator-dependent species. The fruit set in manually cross-pollination flowers (100%) was higher than the manually self-pollinated flowers (30.8%), whereas the control flowers did not set fruits. Females of Centris trigonoides (Apidae, Centridini) were the exclusive pollinators, and the visit rate was low. Several Neotropical orchids of the subtribe Oncidiinae offer floral oils to the pollinators, like the Malpighiaceae familiy. Our results allow inferring that both groups of plants would be part of a guild of species pollinated by oil-collecting bees and that the deceit/pollination syndrome should not be applied to all Oncidiinae flowers.

IMPLIKASI BIOLOGI REPRODUKSI TERHADAP KONSERVASI GENETIK JENIS Santalum album

Santalum album is one of the extinct species which need to be conserved. Therefore, the information of reproductive biology of this species, especially the pollination system can produce important clues in order to conserve it. Preliminary study of pollination system of S. album was conducted at ex-situ conservation plot at Watusipat, Gunung Kidul, Yogyakarta. The observations showed that S. album flowers categorised as protandrous, which structured acropetally; this structure may lead self-pollination within a spike. However, result from artificial pollination showed that S. album was a predominantly out crossing species. Very low level of seeds setted from self-pollinated flowers indicated that pollinator was needed for reproduction process. Observation revealed that European honey bee (Apis mellifera) was one of potential pollinating agents.

The reproductive biology of Cybistax antisyphilitica (Bignoniaceae), a characteristic tree of the South American savannah-like “Cerrado” vegetation

Bignoniaceous woody species are very important ecological components of neotropical forests, but the reproductive biology of many species, such as Cybistax antisyphilitica, remains virtually unknown. Most species of Bignoniaceae are characteristically self-sterile, despite typically exhibiting normal pollen tube growth throughout the style, combined with slow rates of ovule penetration, fertilisation and endosperm initiation in selfed pistils. Uniform abortion occurs within a few days of anthesis, indicating the occurrence of late-acting self-incompatibility (LSI). However, breeding system studies have been performed in fewer than 7% of species, and other types of breeding systems (e.g., self-compatibility and apomixis) have been reported in this family. In the present study, the reproductive biology of C. antisyphilitica was investigated by field observation of flower visitors and floral events. Moreover, reproductive biology of this species was examined through experimental pollinations, analyses of pollen tube growth and ovule penetration using fluorescence microscopy, verification of pistil longevity, and a histological analysis of unpollinated vs. self-pollinated pistils. Finally, morphological aspects, quantities and germination were investigated in seeds that resulted from different pollination treatments. Natural pollination was effected by large- and medium-sized bees, and their visiting behaviour favours a high proportion of geitonogamy and no pollen limitation. Self-pollinated flowers produced no fruits, and all of the characteristic post-pollination events cited above were verified, witnessing the occurrence of LSI with post-zygotic rejection of selfed pistils in C. antisyphilitica. Although some indications of extended pistil longevity were found in selfed pistils, this feature seemed to be affected by unidentified environmental factors. The seeds were always monoembryonic and with high viability. A larger variation in the number of viable seeds was found in fruits derived from natural pollination. A low fruit set was observed after both natural and cross-pollination, and most crossed fruits underwent abortion at several points during the juvenile phase, even when protected against herbivory. The formation of surplus flowers/juvenile fruits and the apparently wasteful selfing mechanism control implied in LSI are discussed in the context of the perennial life style of tropical woody plant species.

English

The fertilization biology of eight sweet cherry cultivars (0900 Ziraat, Lambert, Sunburst, Lapins, Starks Gold, Bing, Chelan and Summit) was studied. Pollen viability was determined with triphenyl tetrazolium chloride (TTC) and fluorescein diacetate (FDA) tests. Pollen germination tests were carried out by hanging drop method on 0, 5, 10, 15 and 20% sucrose solutions. Pollen quantity and pollen morpholo-gical homogeny were determined by hemocytometry method. Pollen tube growth and fruit set ratios of open-pollinated and self-pollinated flowers were also explored. Using TTC and FDA tests, the highest pollen viability rate was obtained with cultivar Sunburst; however, higher pollen germination ratios were obtained with cultivar Lapins and Bing. Starks Gold and Summit cultivars produced more amount of pollen than the other cultivars. A high pollen morphological homogeny was found for all the cultivars. In self, cross and open pollinations, pollen tubes reached the ovules in 2 to 5 days. The pollen tubes of the self pollinated self-fertile cultivars reached the ovule in a less time. Fruit set ratios of the cross-pollinated combinations varied between 0 and 40%. In comparison with self-incompatible cultivars, fruit set ratios of self-fertile cultivars were higher.   Key words: Sweet cherry, pollination, pollen tube growth, fruit set.

Reproductive biology of Echinodorus grandiflorus (Alismataceae): evidence of self-sterility in populations of the state of São Paulo

Abstract The reproductive biology and the pollination of Echinodorus grandiflorus (Cham. & Schltdl.) Micheli were studied in populations native to interior of the State of São Paulo, Brazil. This species blossoms in summer and its flowers offer both nectar and pollen as rewards to pollinators. Nectar is produced in nectaries located at the base of the marginal carpels, opposite the petals. However, the effective pollinators (social and solitary bees), were recorded collecting pollen only. Visits, which can last from one or a few seconds to more than one minute, occur during the whole flower lifespan. Each flower opens at about 5:30 a.m. and lasts circa eight hours. All plants in the studied populations produce only hermaphrodite flowers. Percentage of pollen viability is 75%. The studied populations are self-incompatible and, as a consequence, pollinators are needed to transfer pollen among individuals. In natural conditions and after hand cross-pollinations, all receptacles presented mature achenes. Based on the analyses of pollen tube growth from hand self-pollinated flowers, and as a consequence of achenes abortion circa 30 days after self-pollinations, the populations of E. grandiflorus studied apparently presents a mechanism of late-acting self-sterility.

Pollination and reproductive biology of thirteen species of <i>Begonia</i> in the Serra do Mar State Park, São Paulo, Brazil

The reproductive biology of 13 monoecious species of Begonia that occur in the Serra do Mar State Park, São Paulo, Brazil, was investigated. These species flower annually and present flowers with mostly white tepals, sweet odour, pollen as a reward but no nectar, numerous yellow stamens, and yellow styles. Anthesis is diurnal and floral duration is long (6 - 15 days). The unusual appearance of pistillate flowers of these species supports the view that they are intersexual mimics of the staminate flowers. Despite consistently high levels of fruit-set, none of the 11 species tested proved to be apomictic. In contrast to earlier reports of self-compatibility in Begonia, self-pollinations of B. integerrima and B. itatinensis produced no fruits or seeds, and the complete absence of pollen tubes in the styles of self-pollinated flowers of B. integerrima suggests that the species is self-incompatible. Flowers pollinated under natural conditions showed many pollen tubes that reached ovules, suggesting that adequate numbers of compatible pollen grains had been transported by pollinators. The principal pollinators were bees of the Apidae and Halictidae. Ten species of bees were observed to visit eight species of Begonia, and pollen collection occurred by vibration, except for Trigona spinipes. Visits to rewarding staminate flowers were significantly more frequent than visits to unrewarding pistillate flowers. Duration of visits to pistillate flowers also was significantly shorter than the duration of visits to staminate flowers. We conclude that visits to pistillate flowers occur by mistake but with sufficient frequency to allow for successful reproduction in natural populations of these species.

Late-acting self-incompatibility in Acca sellowiana (Myrtaceae)

Acca sellowiana (Berg) Burret is a predominantly allogamous species with hermaphrodite flowers that has barriers to self-fertilisation such as dichogamy by protogyny and self-incompatibility. This study aimed to identify when self-incompatibility occurs in A. sellowiana flowers submitted to self-pollinations. Pollinations were made using nine known self-incompatible accessions in several treatments including manual cross-pollination, manual self-pollination, no pollination and natural pollination. Flowers were pollinated and pistils collected at times ranging from 1 to 30 days after pollination (DAP). In both cross- and self-pollinations the fertilisation occurred from 18 DAP and the zygote was visualised at 24 and 26 DAP, respectively. The abscission of the self-pollinated flowers increased from 26 DAP onwards, when significant differences (P < 0.05) were found for the percentage of abscission among self-pollinated and cross-pollinated flowers. At 30 DAP, 72% of self-pollinated flowers were abscised. The size of ovules and ovaries of self-pollinated flowers showed no significant difference from those of non-pollinated flowers throughout 30 DAP, while those from cross-pollinated flowers were significantly larger (P < 0.05) than the other treatments from 22 and 24 DAP, respectively. After 40 DAP, there was no fruit development in self-pollination and non-pollination treatments. Our study brings greater clarity to the mechanism of self-incompatibility in A. sellowiana, indicating late-acting self-incompatibility occurring through the rejection/abscission of self-pollinated flowers precisely after syngamy and zygote formation.