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Inflorescence Size: Test of the Male Function Hypothesis

Diane R. Campbell
American Journal of Botany
Vol. 76, No. 5 (May, 1989), pp. 730-738
Stable URL: http://www.jstor.org/stable/2444419
Page Count: 9
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Inflorescence Size: Test of the Male Function Hypothesis
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Abstract

One explanation for low fruit sets in plants with hermaphroditic flowers is that total flower production by a plant is controlled primarily by selection through male function. This male function hypothesis presupposes that success in pollen donation increases more strongly with flower number than does seed set. I tested this prediction by measuring male and female components of reproductive success as functions of flower number in natural populations of the self-incompatible, perfect flowered plant, Ipomopsis aggregata. Fruit set in this humming-bird-pollinated plant averaged 4.9 to 40.3% across the 4 years of study. Both the total amount of pollen donated and the total amount received, as estimated by movement of fluorescent powdered dyes, increased linearly with number of flowers on a plant. Total seed production, however, increased disproportionately quickly because plants with larger floral displays were more likely to set at least one fruit. An estimate of the functional femaleness of a plant, based on pollen donation and seed production, increased with flower number. These results do not support the male function hypothesis.

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