Insect pollination of pansies (viola spp.)
1965
Veerman, A. | ZON, J.C.J.
Experiments with caged flowers proved that insect pollination is necessary before pansies (Viola spp.) set seed. Observations on insects visiting pansy fields grown in the Netherlands for seed production made it clear that bumble-bees (Bombus spp.) and moths of Plusia gamma were the only efficient pollinators, as pansy pollen could be found on the proboscis immediately after visiting the flowers. Photographs (Fig. 2) show that the tongues of the pollinating bumble-bees are long enough to reach the nectar in the spur. Studies on the behaviour of the pollinators proved that the visiting habit shows a remarkable constancy throughout the season, as the number of flowers visited per plant did not increase with increasing numbers of flowers per plant. In about 60 per cent of the cases only one flower per plant was visited, regardless of the species of the insect. If a pollinator leaves a flower, in 40 to 45 per cent of cases it visits another flower of the same plant, while in the other cases it flies to neighbouring plants, or plants farther away. At 40 per cent of the visits self-pollination may occur between two flowers of the same plant, if no pollen of former visits is still present on the proboscis. No interspecific difference in visiting behaviour was found. Pollinating insects when undisturbed cover rather short distances. This makes it improbable that contamination by pollination between different varieties frequently occurs.
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