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Abstract Detail

Pollination Biology

Vance, Nan [1], Bernhardt, Peter [2], Edens, Retha [3], Smith, Jane [4].

Pollination ecology and factors affecting pre-zygotic processes in Cypripedium montanum, the mountain lady’s slipper orchid.

The non-rewarding orchid Cypripedium montanum Douglas ex. Lindley is widely but patchily distributed in western North America and appears to be in decline over parts of its range. Reproductive success varies widely and the contribution of pollination success to its overall survival has been speculative. Fruit-to-flower ratio can be relatively high but varies across years and among locations. Determining cause and effect is problematic as the pollination system has not been studied. We investigated how variation in the orchid’s pollinators and floral traits may relate to reproductive success. Based on pollen load, the pollination vectors of this species are primarily small, generalist, female bees in the Andrenidae, Megachilidae, Colletidae, Halictidae and Apidae families. Dimensional measurements of entrance orifice and labellum vary widely among flowers. Evidence of pollen on insects and insect size indicate that the pollinators that most closely fit the dimensions of the exit orifice are the most effective at pollen transfer. For a non-rewarding orchid with low visitation rates, a larger pollen load on fewer insects may increase pollination success. Thus, attracting multiple species of pollinators may ensure that an optimally sized pollinator is available to accommodate any dimensional differences in floral reproductive structures among plants and from year to year. After the flower’s stigma receives pollen, and anthers have senesced, the inferior ovary expands. However, the mechanism of floral senescence may be delayed for up to three weeks because it takes about two weeks for the growing pollen tubes to enter the ovaries. Microphotographic analyses of pollen tubes and post zygotic embryonic cells suggest that ovules are still maturing post-pollination. This is a critical time when excessive drought or insolation could cause premature senescence. Analysis of post-zygotic effects may further identify the influence of pollen load on reproductive success.

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1 - PNW Research Station, 3200 SW Jefferson Way, Corvallis, Oregon, 97331, USA
2 - Saint Louis University, Department of Biology, 3507 Laclede Avenue, St Louis, Missouri, 63103-2010, USA
3 - Saint Louis University, Department of Biology, 3750 Lindell Blvd, St. Louis, Missouri, 63103, USA
4 - Kelsey Creek Laboratory, P.O. Box 2396, Issaquah, Washington, 98027, USA

Cypripedium montanum.

Presentation Type: Oral Paper:Papers for Topics
Session: CP22
Location: Lake Ontario/Hilton
Date: Tuesday, July 10th, 2007
Time: 10:45 AM
Number: CP22010
Abstract ID:1003

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