Morph Differences and Honeybee Morph Preference in the Distylous Species Fagopyrum esculentum Moench

Abstract

The relatively low reproductive success of buckwheat (Fagopyrum esculentum Moench, Polygonaceae) is poorly understood. The question arises as to whether this distylous species is pollen or resource limited. We investigated the reproductive biology of buckwheat under controlled conditions in growth rooms and in the field in central Belgium in order to determine whether floral morph and pollination events may affect its reproductive success. In controlled conditions, flowering phenology and flower morphology of the two floral morphs did not differ. However, thrum flowers produced larger and fewer pollen grains and secreted more nectar, with a higher proportion of sucrose, than pin flowers. In the field, thrum flowers were preferentially visited by honeybees, but fewer pollen grains were deposited on their stigmas. However, numbers of pollen tubes growing in styles, seed set, and seed weight did not differ between morphs. Seed set was low under field conditions and did not increase after hand cross-pollinations, suggesting that there was no pollen limitation. These results indicate that factors other than floral morph or pollination events were governing female fertility in buckwheat.

Contribution of small insects to pollination of common buckwheat, a distylous crop

“…A single plant produces multiple inflorescences over a period of 25–30 days, but each flower is open and receptive for 1 day (Free, 1993). Cawoy et al (2006) reported that average gynoecium lengths of pin and thrum flowers are 2.58 and 1.41 mm, respectively, and stamen lengths are 1.73 and 2.51 mm, respectively. Flowers produce nectar secreted by glands at the base of the ovary, which attracts many insects.…”

“…We also recorded flower morphs (pin or thrum) on which the insects were captured. In each field, insects were sampled for 15 min between 9:00 h and 12:00 h. The period was set, based on previous work on flower‐visiting insects and pollen availability at different times during the day (Namai, 1990; Bjorkman, 1995 a ; Cawoy et al , 2006). We conducted three trials of the 15‐min sampling for each of our 15 study fields in which the sampling time was between 9:00 h and 12:00 h and the order was randomised.…”

“…We observed and measured the sizes of pollen grains from both flower morphs. Pollen grains of thrum flowers were larger than those of pin flowers (Cawoy et al , 2006). To distinguish the size of pollen grains between the two flower morphs in our study plants, we selected five individual plants for each of the flower morphs and sampled three fresh individual flowers per selected plant in each field.…”

Effects of floral resources on the efficacy of a primary parasitoid and a facultative hyperparasitoid

“…Buckwheat Fagopyrum esculentum Moench (Polygonaceae) is a fast‐growing, annual plant that produces hexose‐dominant nectar, with fructose making up more than 50% of the sugar at peak flowering (Bowie, Wratten, & White, ; Cawoy et al, ; Cawoy, Ledent, Kinet, & Jacquemart, ; Lee, Heimpel, & Leibee, ). Common vetch Vicia sativa L. (Fabaceae) is a leguminose annual plant often grown for seed, pasture, hay and as green manure due to its strong nitrogen‐fixing capacity (Acikgoz & Rum‐Baugh, ).…”

Dichotomy of male and female responses to hoverfly-driven cues and floral competition in the parasitoid wasp Aphidius ervi Haliday

“…Plants were chosen at random from an experimental population of twelve F. esculentum, with any individual plant only used once in any 24 h period. This 24 h period was considered sufficient time for any scent marking by hoverflies to have dissipated (Reader et al, 2005) and for F. esculentum nectar to have replenished itself in plants exposed to hoverflies (Cawoy et al, 2006). For the hoverfly exposed treatment plants were placed within a cage housing three sexed pairs of E. balteatus for 24 h prior to use.…”