Abstract
Bee-pollinated crops in landscapes with a low abundance of bees suffer from insufficient pollination. The present study investigates the effect of wild bee pollination on fruit and seed production in okra, Abelmoschus esculentus (L.) Moench. The study was conducted in a home garden, where an okra field was established for three pollination trials each to include 40 okra plants. For each trial, three sets of 25 flower buds were selected and tagged. One set was covered to deter bees, another set was kept open to enable bee visits and the other set was cross-pollinated by hand. Of the two species of bees, Tetragonula iridipennis (Smith) visited flowers for nectar while Lithurgus atratus Smith collected and carried pollen grains. The period of stigma receptivity and pollen availability coincided with the highest activity of L. atratus from 10.00 a.m. to 12.20 p.m. Bee-pollinated flowers had significantly enhanced okra pod length and diameter, seed number and seed germinability compared to the trial with flowers covered to deter bees. Hand pollinated flowers also produced significantly longer pods and a higher number of seeds with higher germinability. Although there was no significant difference in pod length and diameter and seed number between hand pollination trial and bee-pollinated trial, germinability of bee-pollinated seeds was significantly higher. Present study highlights the importance of the wild bee, L. atratus to enhance pod size, seed number and seed germinability in okra in Kurunegala, Sri Lanka.
Highlights
Bees visit plants to collect pollen and nectar as food for them and provision their nests as food for the young (Michener 1974; Roubik 1989)
Of the two species of bees visiting okra flowers, Lithurgus atratus was the only species with the ability to collect and carry pollen on its body
Close observations of foraging behaviour of T. iridipennis is necessary to specify their role in pollinating okra
Summary
Bees visit plants to collect pollen (source of protein) and nectar (source of carbohydrate) as food for them and provision their nests as food for the young (Michener 1974; Roubik 1989). Bees are the most important group of pollinators, visiting more than 90% of the leading 107 global crop types (Klein et al 2007). Wild bees are highly diverse, differing widely in their forage preferences and flight times depending on weather conditions. Bees have varied relationships with flowers based on the type of floral resource they specialize on. Many solitary bees are resource specialists for pollen, and rarely for nectar (Wcislo & Cane 1996). The pollen relationships of solitary bees, unlike those of social bees, vary from being general (visiting a wide variety of unrelated flower types belonging to several families) to a highly specialized. Based on the diversity of pollen gathered, bees are termed polylectic, oligolectic and monolectic.
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