Good Pollinators Research Articles

Floral biology, pollination ecology and seed production of the ornamental plant Salvia splendens Sello

SummaryIn this paper, the floral biology and pollination ecology of Salvia splendens are described. All flower characteristics (red corolla, large tubular flowers with abundant but dilute nectar) indicate that S. splendens is adapted to hummingbird pollination. Honeybees, however, were also found to be good pollinators of this plant. Apis mellifera was equally effective in pollinating S. splendens as hand pollination and open pollination, resulting in a 300% increase in seed set compared with bagged control plants. The much smaller stingless bee Tetragonisca angustula was not an effective pollinator of these flowers since during visitation its body failed to touch the stigma. Although pollination seemed not to be the only limiting factor in seed production, external pollinators enhance seed production in S. splendens, and Apis mellifera is an effective, commercially available pollination agent of this economically important ornamental plant.

Exploring the ‘Most Effective Pollinator Principle’ with Complex Flowers: Bumblebees and Ipomopsis aggregata

The ‘most effective pollinator principle’ implies that floral characteristics often reflect adaptation to the pollinator that transfers the most pollen, through a combination of high rate of visitation to flowers and effective deposition of pollen during each visit. We looked for the expected positive correlation between quantity and quality of visits in Ipomopsis aggregata, whose red, tubular flowers are considered to be adapted to hummingbirds. Hummingbirds were indeed the most common floral visitors in 5 years of observation. However, long-tongued bumblebees deposited on average three-times as much outcross pollen per visit to virgin flowers, and elicited four-times as much seed production, as did hummingbirds. Hence visitors that are relatively infrequent, and unexpected given the ‘pollination syndrome’ of the plant, can be surprisingly good pollinators. One interpretation of this observation is that natural selection favours a specialized floral morphology that excludes all but a single type of visitor, but that there are constraints on achieving this outcome. An alternative is that selection favours some degree of floral generalization, but that flowers can retain features that adapt them to a particular type of pollinator in spite of this generalization.

Does Low Biodiversity Resulting from Modern Agricultural Practice Affect Crop Pollination and Yield?

This Botanical Briefing examines the hypothesis that modern agricultural practice affects natural biotic pollination to the extent that crop yields suffer. Few staple foods depend on animal pollination and relatively few other crops are totally dependent on animal pollination. However, there are many crops of local economic importance whose yield or quality may be enhanced by good pollinator activity: studies of these deserve more attention. Amongst those cases already documented, intensification and habitat loss are the most frequent causes of pollinator impoverishment reducing crop yield. As yet there is no clear example of low crop yield resulting from the effect of pesticides or transgenic plants on pollinators, and only one example involving herbicides, although each of these agents can affect populations of crop pollinators.

Position‐dependent reproductive success of flowers in Dactylorhiza maculata (Orchidaceae)

Abstract1. This study explores the importance of flower position for reproductive success of individual flowers of the deceptive terrestrial orchid, Dactylorhiza maculata (L.) Soó.2. Upper flowers had smaller lips and produced lighter pollinia than those in other parts of the inflorescence, probably due to architectural effects.3. Dry weight of seed capsules decreased from bottom to top in the inflorescence in both open‐pollinated and hand‐pollinated plants. However, removal of flowers from the middle and lowest parts of the inflorescence considerably increased seed production of the upper flowers. Decreased seed set was due to decreased resource availability because of the long maintenance time of opened but not pollinated lower flowers.4. Experimental self‐pollination resulted in reduced seed set compared to that following pollination with cross‐pollen, but decreased seed set was independent of flower position within an inflorescence.5. Dactylorhiza maculata with large inflorescences did not have better pollination success. The production of more flowers than the plant is able to fully support may have evolved as an ovary reserve in case of flower herbivory, or as a ‘bet‐hedging’ strategy through which the plant can increase seed production in years with good pollinator availability.

A comparison of two pollinators: the introduced honey bee Apis mellifera and an indigenous bee Centris tarsata on cashew Anacardium occidentale in its native range of NE Brazil

1. Aspects of the flowering biology of wild cashew Anacardium occidentale, an andro monoecious, self‐fertile tree, were studied in the north‐east of Brazil, where this species is endemic. Comparison was made among two bee species, Apis mellifera and Centris tarsata, in their pollination of cashew flowers using a number of measures including single bee visits to marked flowers. 2. Cashew flowering is protandrous within a day. Male flowers greatly outnumber hermaphrodite flowers. Stigmas lose receptivity rapidly and pollen is quickly removed from anthers yet flowers remain intact for several days. 3. Only females of C. tarsata collected pollen from cashew flowers, and then only from male flowers. The similar foraging behaviour of the nectar collectors of the two bee species under investigation when visiting hermaphrodite cashew flowers suggests that they may both act as good pollinators. 4. We develop an index of efficiency of pollen removal from anthers (PREi) whereby the relative benefits of flower visitors to a component of a plant’s male reproductive success can be quantified. 5. Comparisons of single bee visits to flowers with unvisited flowers and others receiving unlimited visits were used to show that: C. tarsata pollen collectors were more efficient than nectar collectors of either bee species at removing pollen from anthers; nectar collectors of both bee species had similar pollen removal efficiencies; C. tarsata was more efficient at depositing pollen on stigmas than A. mellifera; both bee species had statistically similar efficiencies at setting seed. 6. The indices of efficiency for some of the stages in the pollination of cashew suggest that C. tarsata flower visits may enhance plant reproductive success over flower visits by A. mellifera but that both bee species may be suitable for the pollination of commercially grown cashew. 7. Despite cashew’s single ovule per flower, high nut set demands a high rate of pollinator visitation during the peak time of stigma receptivity. Provision of additional bee pollination in commercial orchards is recommended to obtain good nut yields.

Practical science—research helping beekeepers 2. Colony manipulations for honey production

Because they are good pollinators, honey bees contribute profoundly to world food production. Because they flourish in hives, they provide hours of fun and relaxation to hobby beekeepers. Because they are social and manageable, honey bees are a favoured laboratory animal for scientists and educators. But for most people, honey bees are what their name says—bees that make a lot of honey. Optimizing honey production has been the focus of much research over several decades, and there are many success stories in which scientists and beekeepers identified a principle of bee biology and developed it into a profitable practice. I describe some of these success stories here. Honey production is a function of local weather, flora, bee densities, bee genetics, colony health, and colony manipulations by the beekeeper. I limit this discussion to colony manipulations.

Investigation on the Fertilization Biology of Santa Maria and June Beauty Summer Pear Cultivars

In this study, fertilization biology of Santa Maria and June Beauty summer pear cultivars, grown under Adana ecological conditions, were investigated. In addition to these two cultivars Prococe di Fiorano was taken as pollinators. In order to determine the pollinator ability of these cultivars, the polen viability, germination capacity and production level of pollens were tested in vitro. Viability of the pollens was determined by TTC and FDA tests. In vitro pollen germination experiments with 'hanging drop' method were done in 0, 5, 10, 15 and 20 % sucrose solutions. In addition, pollen production of the cultivars were detemined by using 'hemacytometric method'. The percentage of fruit-set obtained from free-, self- and cross-pollination experiments, determined in vitro. In order to determine the parthenocarpic fruit settings ability, the flowers were emasculated and isolated. Additionally, the fruit sizes and the number of seeds per fruit determined in all experiments. Santa Maria has given the best results on the pollen viability and germination test. The most suitable pollen germination media were 10 and 15 % sucrose solutions depending on the cultivars. The highest pollen production level was obtained from Santa Maria. After cross-pollinations, it was found that Santa Maria and June Beauty were good pollinators for each other. Moreover, Santa Maria cv. was found to have a tendency for parthenocarpic fruit set.

Some aspects of cross-pollination in wheat (Triticum aestivum L.) 1. Pollen concentration in the field as influenced by variety, diurnal pattern, weather conditions and level as compared to the height of the pollen donor

For the large-scale production of hybrid seed the cross-fertilizing capacity of wheat must be increased. Breeding good pollinators is, therefore, a necessity. Five spring wheat varieties were examined for differences in pollen shedding capacity under normal field conditions. The examination was carried out by collecting pollen on object slides every hour from 06.00 till 20.00 h during flowering. In general, the variety Peko proved to be the best shedder of pollen, while Opal was the worst. Gaby, Jufy I and Orca were intermediate. Consistent results were hard to obtain mainly due to varying weather conditions. It was established that pollen is released throughout the whole period of daylight. The maximum release of pollen, however, occurred from 08.00 till 11.00 h. A less pronounced and much smaller peak was noticed from about 15.00 till 18.00 h. Most pollen appeared to be released at a temperature of 16–20°C and a relative humidity of 70–75%. Although there seems to be some relationship between the diurnal pattern of the pollen release and the indicated values of these meteorological factors, one cannot say that the former is entirely determined by the latter. It has been suggested in the literature that a male-sterile parent that is shorter than its pollinator would be most likely to produce good seed set in the hybrid wheat seed production field. Investigations showed that a greater concentration of pollen was found below the ear level of pollinator plants than at or above ear level.