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Stigma behavior in Mimulus aurantiacus (Scrophulariaceae).
1Department of Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0116.
American Journal of Botany
|August 17, 1999
Summary
Bush monkey flower stigma closure protects against self-pollination but doesn't improve seed set. This rapid response to touch, while slower to pollen, has no negative impact on female reproductive fitness.
Area of Science:
- Plant reproductive biology
- Pollination ecology
- Plant-pollinator interactions
Background:
- The bilobed stigma of many Scrophulariales species closes upon tactile stimulation by pollinators.
- In Mimulus aurantiacus, stigma closure is rapid (seconds) upon touch.
Purpose of the Study:
- Investigate proximate causes of stigma closure and reopening in Mimulus aurantiacus.
- Evaluate potential costs and benefits of stigma closure for female fitness.
Main Methods:
- Stimulating M. aurantiacus stigmas with touch and/or pollen.
- Observing stigma closure and reopening times.
- Manipulating stigmas to prevent closure during natural pollination.
- Assessing pollen load and seed set.
Main Results:
- Stigma closure is triggered by touch and pollen, with pollen-induced closure being slower.
- Unpollinated stigmas reopen faster (2.5-4.5 h) than pollinated ones (20-28 h).
- Stigma closure does not increase pollen capture or seed set; it reduces pollen load but has no negative fitness effects.
Conclusions:
- Stigma closure in M. aurantiacus is a rapid response to pollination.
- Closure does not enhance reproductive success and may reduce pollen receipt.
- The adaptive significance of stigma closure requires further investigation despite its lack of negative fitness consequences.