New Zealand Journal of Botany abstract
B97049Received 16 July 1997; accepted 12 March 1998
Inflorescence photosynthesis and investment in reproduction in the dioecious
species Aciphylla glaucescens (Apiaceae)
K. P. HOGAN
Landcare Research
P.O. Box 69
Lincoln, New Zealand
M. B. GARCíA
Estación Biológica de Donñana (CSIC)
Apartado 1056
E-41080 Sevilla, Spain
J. M. CHEESEMAN
Department of Plant Biology
University of Illinois
505 S. Goodwin
Urbana
IL 61801, USA
M. D. LOVELESS
Department of Biology
College of Wooster
Wooster
OH 44691, USA
Abstract The differences in the costs of reproduction between
males and females of dioecious plants should lead to differences in life
history evolution, but photosynthesis of reproductive structures can reduce the
cost of these structures. We hypothesised that the greater costs of
reproduction would select for greater photosynthetic capacity in reproductive
structures of female plants of the dioecious species
Aciphylla
glaucescens. However, measurements of gas exchange using a portable
infra-red gas analysis sytem showed that the photosynthetic capacity of male
inflorescences is greater, and their total mass is half that of females. Thus,
male inflorescences contribute more to their own carbon and energy costs.
Estimates of the contribution of inflorescence photosynthesis suggest that much
of the reproductive biomass is attributable to import of photosynthate from the
leaves. Total nitrogen investment in reproductive structures was much greater
in females. Life history differences between males and females may be driven by
nitrogen or ecological factors rather than by carbon acquisition or energy
requirements.
Keywords dioecy; biomass; nitrogen; gender dimorphism; fruit
photosynthesis
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