Gender-specific physiology in trembling aspen, Populus tremuloides (Salicaceae).

Abstract

Male and feamle clones of trembling aspen, Populus tremuloides, were studied on the Pellston Plain in northern lower Michigan to determine if there were any physiological differences between sexes. Measurements included photosynthetic rate (A), stomatal conductance (g), water-use efficiency (A/g), chlorophyll concentration, specific leaf area, water potential, and stomatal density. Females had greater stomatal conductance, lower water-use efficiency, and higher specific leaf area than males. There were no signficant differences between males and females in the photosynthetic rate per area, chlorophyll concentration, mid-day or pre-dawn water potentials, or stomatal density. Females may exhibit these physiological differences to compensate for the greater cost of reproduction. Because the Pellston Plain has such a low density of clones of a relatively young age, females may not currently be experiencing the tradeoffs associated with gender-specific physiological differences, such as greater differential mortality with greater competition.