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Ecological Section

Bala, Janet [1], Williams, C.F. Rick [1], McGonigle, T.P. [1].

Effects of nutrient limitation on sex allocation in gynodioecious Geranium richardsonii (GERANEACEAE).

Nutrient limitation may be an important factor in the evolution of plant sexual systems. Gynodioecy is one form of sexual expression in which both female and hermaphroditic (male and female) plants exist in a population. Understanding how resources allocated to male reproductive parts affect resources allocated to female reproduction will aid our understanding of the paradox of gynodioecy. The maintenance of females created an evolutionary paradox, in that females must compensate for their lack of gene transmission through male function by increased seed production or higher quality of offspring. This project investigated the effects of nutrient limitation on sex allocation and reproductive success in gynodioecious Geranium richardsonii. Floral parts measured at different stages of plant growth allowed comparisons of allocation to male versus female function. Cloned plants from two populations grown from seeds collected from wild populations of Geranium richardsonii were grown in a greenhouse setting at Idaho State University. Using a randomized complete block design, six treatment groups were established, including a low and high nitrogen and a zero, low and high phosphorus. Four hermaphrodites and four females per population were used for each treatment. Flowers were collected at different times during the growing season and dissected into component parts. After dissection, the individual parts were dried and weighed to the nearest microgram. The dried samples were digested and analyzed for both nitrogen and phosphorus concentration. Nutrient limitation has a significant effect on floral biomass and the nutrient limitation has a greater effect on patterns of allocation to female function (pistils) than to male function (stamens).

1 - Idaho State University, Department of Biological Sciences, Campus Box 8007, Pocatello, Idaho, 83209-8007, USA

Sex allocation
nutrient limitation

Presentation Type: Poster
Session: 32-43
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM
Abstract ID:794

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