Do food trichomes occur in Pinguicula (Lentibulariaceae) flowers?

Background and Aims Floral food bodies (including edible trichomes) are a form of floral reward for pollinators. This type of nutritive reward has been recorded in several angiosperm families: Annonaceae, Araceae, Calycanthaceae, Eupomatiaceae, Himantandraceae, Nymphaeaceae, Orchidaceae, Pandanaceae and Winteraceae. Although these bodies are very diverse in their structure, their cells contain food material: starch grains, protein bodies or lipid droplets. In Pinguicula flowers, there are numerous multicellular clavate trichomes. Previous authors have proposed that these trichomes in the Pinguicula flower play the role of ‘futterhaare’ (‘feeding hairs’) and are eaten by pollinators. The main aim of this study was to investigate whether the floral non-glandular trichomes of Pinguicula contain food reserves and thus are a reward for pollinators. The trichomes from the Pinguicula groups, which differ in their taxonomy (species from the subgenera: Temnoceras, Pinguicula and Isoloba) as well as the types of their pollinators (butterflies/flies and bees/hummingbirds), were examined. Thus, it was determined whether there are any connections between the occurrence of food trichomes and phylogeny position or pollination biology. Additionally, we determined the phylogenetic history of edible trichomes and pollinator evolution in the Pinguicula species. Methods The species that were sampled were: Pinguicula moctezumae, P. esseriana, P. moranensis, P. emarginata, P. rectifolia, P. mesophytica, P. hemiepiphytica, P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia, P. gigantea, P. lusitanica, P. alpina and P. vulgaris. Light microscopy, histochemistry, and scanning and transmission electron microscopy were used to address our aims with a phylogenetic perspective based on matK/trnK DNA sequences. Key Results No accumulation of protein bodies or lipid droplets was recorded in the floral non-glandular trichomes of any of the analysed species. Starch grains occurred in the cells of the trichomes of the bee-/fly-pollinated species: P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia and P. gigantea, but not in P. alpina or P. vulgaris. Moreover, starch grains were not recorded in the cells of the trichomes of the Pinguicula species that have long spurs, which are pollinated by Lepidoptera (P. moctezumae, P. esseriana, P. moranensis, P. emarginata and P. rectifolia) or birds (P. mesophytica and P. hemiepihytica), or in species with a small and whitish corolla that self-pollinate (P. lusitanica). The results on the occurrence of edible trichomes and pollinator syndromes were mapped onto a phylogenetic reconstruction of the genus. Conclusion Floral non-glandular trichomes play the role of edible trichomes in some Pinguicula species (P. agnata, P. albida, P. ibarrae, P. martinezii, P. filifolia and P. gigantea), which are mainly classified as bee-pollinated species that had originated from Central and South America. It seems that in the Pinguicula that are pollinated by other pollinator groups (Lepidoptera and hummingbirds), the non-glandular trichomes in the flowers play a role other than that of a floral reward for their pollinators. Edible trichomes are symplesiomorphic for the Pinguicula species, and thus do not support a monophyletic group such as a synapomorphy. Nevertheless, edible trichomes are derived and are possibly a specialization for fly and bee pollinators by acting as a food reward for these visitors.

Nectar secretion and pollen production in Hyacinthus orientalis ‘Sky Jacket’ (Asparagaceae)

Flowering, nectar secretion, and pollen production in <em>Hyacinthus orientalis</em> ‘Sky Jacket’ (Asparagaceae) were studied between 2013 and 2015 in Lublin, SE Poland (51°16' N, 22°30' E). The flowering was weather-dependent. It started at the beginning of April or at the end of the month and lasted 14–24 days. The mass of nectar, sugar concentration in the nectar, nectar sugar mass, anther size, and pollen mass in flowers all depended on the flower position in the inflorescence and differed significantly between the years of study. The greatest mass of sugars and pollen was recorded in low-positioned flowers. On average, <em>H. orientalis</em> ‘Sky Jacket’ produced 1.63 mg of sugars and 3.51 mg of pollen per flower. The floral reward was attractive for <em>Apis mellifera</em> and <em>Bombus</em> spp., which indicate that the species should be propagated not only for its decorative value but also for supporting pollinators in early spring.

Nectar and pollen production of Helianthus tuberosus L. – an exotic plant with invasiveness potential

In Central Europe, Helianthus tuberosus L. is a late summer/autumn bloomer (August/November). The disc florets produce both nectar and pollen. Floral reward is available in male-phase flowers (pollen and nectar) and in female-phase flowers (nectar). The floral reward is attractive to a variety of insect visitors (honey bees, wasps, flies and butterflies). The season of blooming as well as the total sugar yield (25.4 – 47.4 kg ha−1) and pollen yield (57.8 – 212.7 kg ha−1) indicate that H. tuberosus is important in the enhancement of food resources for pollinators. The generative reproduction in H. tuberosus is impaired (the species does not set seeds/fruits). However, due to its attractiveness for a variety of pollinators in both rural and urban areas, the spread of H. tuberosus should be monitored. Moreover, its propagation needs to be attended with restrictions.

Pollination in an endemic and threatened monoecious herb Begonia satrapis C.B. Clarke (Begoniaceae) in the eastern Himalaya, India

Begonia satrapis was studied for its pollination aspects at Sumbuk, Sikkim, India. The floral details and the foraging behaviour of insects visiting the flowers were examined to define the pollination syndrome and its functionality for the success of sexual reproduction in this species. The flowers do not produce nectar and offer only pollen as floral reward to foraging insects. Therefore, male flowers were foraged more for its pollen than the female flowers. There was a significant difference in the visit to male and female flowers by both Apis florea and Bombus breviceps, respectively. The bees spent more time on male flowers than on female flowers. The bees appear to rely on visual stimuli to visit male and female flowers. The plant produces abundant fruit and seed set in both hand and open-pollinations indicating that it is facultatively xenogamous. The female flowers lacking any reward resemble male flowers and in effect are pollinated by deceit.

Nectar and pollen production in ornamental cultivars of Prunus serrulata (Rosaceae)

Planting ornamental species can help to create pollinator-friendly habitats. In the present study the flowering phenology and floral reward (nectar and pollen) in two cultivars of Prunus serrulata (‘Kanzan’ and ‘Amanogawa’) were evaluated in 2014-2015 in the city of Lublin (south-east Poland). On average, the onset of flowering of P. serrulata occurred in the first ten days of April (‘Kanzan’) or at the end of April (‘Amanogawa’), and lasted 8-17 days. In each year of the study, P. serrulata ‘Kanzan’ started flowering 11-18 days earlier than P. serrulata ‘Amanogawa’. The double flowers of P. serrulata ‘Kanzan’ offered only tiny amounts of nectar and pollen. The total mass of sugars was 0.59 mg per flower and that of pollen 0.08 mg per flower. The semi-double flowers of P. serrulata ‘Amanogawa’ produced 4.5 mg of sugars per flower and 0.17 mg of pollen per flower. The frequency of pollinator visits to flowers was low in P. serrulata ‘Amanogawa’ and very low in P. serrulata ‘Kanzan’. Therefore, if pollinator-friendly arrangements are made in urban areas, these cultivars should not be planted.

Honeybee Response to Landing Guides in Flowers of Smithia hirsuta Dalzell, An Endemic Herb of India

Honeybees response to landing guide located on flowers of Smithia hirsuta Dalzell, an endemic herb of India is studied. The bees perceive the colour contrast as landing guide which serve as a map to the concealed floral reward, the nectar. Hence they associate these with nectar and forage precision with maximum energy conservation. Detailed taxonomy of S. hirsuta Dalzell is also provided.